Transposition of the great arteries: clinical guidelines

List of Abbreviations

AV – atrioventricular junction;

Ao – aorta;

AoV – aortic valve;

ACG – angiocardiography;

ACE – angiotensin-converting enzyme;

aPTT – activated partial thromboplastin time;

LVOT – left ventricular outflow tract;

LVOT – left ventricular outflow tract;

PSG – peak systolic gradient;

VSD – ventricular septal defect;

ASD — atrial septal defect;

ESC – European Society of Cardiology;

IMV – invasive mechanical ventilation;

CPB – cardiopulmonary bypass;

IVS – intact ventricular septum;

IMPA – invasive monitoring of pulmonary artery pressure;

CA – coronary artery;

EDV – end-diastolic volume;

EDD – end-diastolic dimension;

CT – Computed tomography;

LV – left ventricle;

PA(T) – pulmonary artery (trunk);

LCA – left coronary artery;

IVS – interventricular septum;

MV – mitral valve;

INR – international normalized ratio;

IAS – interatrial septum;

IAC — interatrial communication;

MRI – magnetic resonance imaging;

HF – heart failure;

PDA – patent ductus arteriosus;

LVOTO – left ventricular outflow tract obstruction;

NICU – Neonatal Intensive Care Unit;

PFO — patent foramen ovale;

RV — right ventricle;

PTI – prothrombin index;

RCA – right coronary artery;

PT – prothrombin time;

CRP – C-reactive protein;

SLA – systemic-to-pulmonary shunt;

TGA – transposition of the great arteries;

TGA – transposition of the great vessels;

EF – ejection fraction;

EchoCG – echocardiography;

ACC – American College of Cardiology;

AHA – American Heart Association;

NYHA – New York Heart Association

Terms and Definitions

Cardiac catheterization and angiocardiography is an invasive diagnostic method for assessing central hemodynamics, involving direct pressure measurement in the heart chambers, blood sampling from them to assess gas composition, and their contrast imaging.

Computed tomography (CT) – a non-invasive diagnostic imaging method that yields a series of submillimeter cross-sectional axial images of human body organs and structures, based on measuring and complex computer processing of X-ray attenuation differences by tissues of varying densities; to improve the differentiation of organs from one another, as well as normal and pathological structures, various contrast enhancement techniques are used with iodine-based radiocontrast agents. To visualize the structures of the cardiovascular system, CT angiography is used—a technique of intravenous bolus injection of a radiocontrast agent into the bloodstream using an intravascular contrast injection system at a preset injection rate and time, based on which computer post-processing with 3D reconstruction builds a three-dimensional model of the heart and vessels.

Magnetic resonance imaging (MRI) – a non-invasive, non-X-ray computer method for obtaining tomographic medical images to study internal organs and tissues, based on the phenomenon of nuclear magnetic resonance and the measurement of the electromagnetic response of atomic nuclei placed in a strong static magnetic field in response to excitation by a specific combination of electromagnetic waves; such nuclei are hydrogen atoms present in the human body as part of water and other substances. MR angiography is a method for imaging the vascular lumen using an MRI scanner. The method allows for the evaluation of both anatomical and functional blood flow characteristics. MR angiography is based on the difference in signal between moving protons (blood) and surrounding stationary tissues, which allows for vascular imaging without the use of any contrast agents—non-contrast angiography (phase-contrast MR angiography). In some cases, intravenous bolus contrast enhancement using gadolinium-based paramagnetic contrast agents is applied.

Critical congenital heart defects — conditions characterized by acute cardiac output deficiency, rapid progression of heart failure, tissue oxygen starvation with the development of decompensated metabolic acidosis, and impaired vital organ function [1].

Patient – an individual to whom medical care is provided or who applies for medical care regardless of the presence of a disease and their condition [2].

Working group on the development/updating of clinical guidelines – a team of specialists working together and in a coordinated manner to develop/update clinical guidelines and bearing joint responsibility for the results of this work.

Condition – bodily alterations arising from the impact of pathogenic and/or physiological factors and requiring medical care [2].

Syndrome is a stable set of symptoms sharing a common pathogenesis [3].

Thesis-recommendation – a statement reflecting the procedure and correctness of performing a particular medical intervention with proven efficacy and safety.

Level of evidence (LoE) is the degree of confidence that the estimated effect of a medical intervention is true [4].

Grade of recommendation (GoR) is the degree of confidence in the reliability of the intervention effect and that adherence to the recommendations will bring more benefit than harm in a specific situation [4].

Echocardiography – an ultrasound method aimed at studying morphological and functional changes of the heart and its valve apparatus.

1. Brief information on the disease or condition

1.1 Definition of the disease or condition

Transposition of the great arteries (TGA) is a group of congenital heart defects belonging to conotruncal anomalies, characterized by atrioventricular concordance and ventriculoarterial discordance [5].

Morphological criteria of the defect [6]:

1. Atrioventricular concordance;

2. Ventriculoarterial discordance;

3. Presence of subaortic conus;

4. Absence or hypoplasia of subpulmonary conus;

5. Presence of mitral-pulmonary fibrous continuity.

Associated defects:

• atrial septal defect;

• patent ductus arteriosus;

• juxtaposition of atrial appendages;

• coronary artery anomalies;

• persistent left superior vena cava;

• atrioventricular valve anomalies;

• right ventricular hypoplasia.

1.2 Etiology and pathogenesis of the disease or condition (group of diseases or conditions)

The main feature of this pathology is that blood circulation in the systemic and pulmonary circuits occurs in parallel rather than in series, as is normal. Deoxygenated blood from the right ventricle enters the aorta. After passing through the systemic circulation, it returns to the right side of the heart. Oxygenated blood from the pulmonary veins returns to the left ventricle and enters the pulmonary artery. Mixing of blood from the two circulatory circuits is only possible if there are communications at various levels (most commonly an interatrial communication or patent ductus arteriosus, less frequently a ventricular septal defect). The degree of arterial hypoxemia depends on the size of the communications and, accordingly, on the volume of mixing of pulmonary and systemic venous blood return. Blood shunting occurs in both directions, since a unidirectional shunt would lead to complete emptying of one of the circulatory circuits [7].

There are two groups of patients. The first group includes patients with an intact ventricular septum (IVS). In so-called "simple transposition," the mixing of venous and arterial blood occurs mainly at the atrial level through a patent foramen ovale (PFO) and to a lesser extent at the great artery level through a patent ductus arteriosus (PDA). Usually, this mixing is minimal (especially with a small "restrictive" interatrial communication), resulting in severe hypoxemia. Intrauterine circulation is not compromised by this anomaly. However, immediately after birth, a life-threatening situation acutely arises due to low systemic arterial blood oxygen saturation. The condition of patients with IVS is more severe than that of patients with a ventricular septal defect (VSD). An exception is patients with a large atrial septal defect. For patients with TGA, surgical correction is indicated at an early age and usually consists of correcting ventriculoarterial discordance. However, in the neonatal period, in the presence of severe arterial hypoxemia and a "restrictive" interatrial communication, a stabilizing procedure—Rashkind balloon atrial septostomy—is often performed prior to radical correction.

The second clinical group is represented by patients with VSD. The mixing of blood from the two circulatory circuits occurs not only at the atrial level (via interatrial communication) and arterial level (via PDA) but additionally at the ventricular level.

Patients with VSD are less cyanotic, but they have a tendency to develop congestive heart failure and pulmonary hypertension, which manifests as early as 3–4 months of life. Therefore, anatomical correction at an early age is also indicated for them.

1.3 Epidemiology of the Disease or Condition

Transposition of the great arteries is the most common cyanotic congenital heart defect after tetralogy of Fallot. It accounts for 2.5–5% of all congenital heart defects. It is often associated with other congenital heart defects, such as VSD (20–45%), left ventricular outflow tract obstruction (5–25%), coronary artery anomalies (25%), coarctation of the aorta (<5%), aortic arch interruption (<1%), and atrial isomerism (<1%). Familial variants of TGA do not occur. Furthermore, no association with known genetic syndromes and chromosomal abnormalities has been established. Males predominate among patients with TGA (2:1). TGA is more common in infants born to mothers with diabetes mellitus [8].

1.4 Features of Coding the Disease or Condition

Q20.3 – Discordant ventriculoarterial connection

1.5 Classification of the disease or condition

Currently, the following classification of transposition of the great arteries is used more often than others [9]:

• with an intact ventricular septum (IVS);

• with IVS and left ventricular outflow tract (LVOT) obstruction;

• with VSD;

• with VSD and LVOT obstruction.

Several approaches have been proposed to systematize the multiple branching variants of the coronary arteries. The "Leiden Convention" is a widely used classification system.

Leiden classification of coronary anatomy [10].

• Sinuses (viewed from the perspective where the aorta comes first, followed by the pulmonary artery)

- sinus 1 – adjacent to the pulmonary artery on the right side from the observer's viewpoint (anatomically left);

- sinus 2 – adjacent to the pulmonary artery on the left side from the observer's viewpoint (anatomically right).

• Coronary arteries:

- right coronary artery;

- anterior descending artery;

- circumflex artery (Cx).

M.N. Yacoub and R. Radley-Smith classification [11].

Type A – normal coronary artery (CA) anatomy. The right and left coronary ostia in this type are located in the centers of the right and left aortic sinuses.

Type B – both CAs arise from a single common ostium located in close proximity to the posterior commissure of the aortic valve in one of the sinuses.

Type C – two coronary artery ostia are located very close to each other in close proximity to the posterior aortic commissure.

Type D – the location of the ostia is similar to that in Type A. The course of the left coronary artery (LCA) is similar to that in Type A, except for the absence of the circumflex branch in its typical location.

Type E – the circumflex artery originates from the right posterior sinus, and its further course is similar to that described in Type G. Another coronary trunk originates from the anterior part of the left sinus, courses anteriorly, and then divides into the main right coronary and anterior descending arteries. The right CA runs along the anterior surface of the outflow tract of the anteriorly positioned ventricle, reaching the right AV groove.

Type F – practically identical to Type D, except for the origin site of the anterior descending artery.

The Marie Lannelongue Hospital classification is based mainly on the course of the coronary arteries and does not emphasize the location of the ostia. Four variants of the coronary artery course are distinguished:

• Normal course (about 60% of all cases);

• Loop course (35%);

• Intramyramidal course (5%);

• Mixed course variant, including intramyramidal and loop courses (0.1%).

The classification of coronary anatomy by the risk level of surgical treatment [12,13] provides for those distribution variants of the coronary arteries that are able to determine the prognosis of arterial switch, namely:

• all coronary arteries originate from a single sinus;

• intramural coronary arteries;

• retropulmonary course of the entire left coronary artery system;

• retropulmonary location of only the circumflex artery;

• left coronary artery or any of its branches originating from sinus 2.

1.6 Clinical presentation of the disease or condition

An infant with TGA is symptomatic from birth. The leading symptom in newborns is cyanosis, the intensity of which does not change significantly with oxygen breathing. Cyanosis may be less pronounced when TGA is combined with a large VSD. In infants with insufficient blood mixing at the septal level, severe arterial hypoxemia, acidosis, and circulatory failure may develop, which are exacerbated by the closure of the ductus arteriosus [14,37].

In adult patients after surgical correction of TGA, clinical manifestations of congestive heart failure (usually left ventricular, but right ventricular is also possible) and coronary ischemia are possible. The occurrence of long-term cardiac arrhythmias is also possible, which may be accompanied by complaints of skipped heartbeats and palpitations (with varying severity of clinical symptoms). In patients after the Rastelli procedure, clinical symptoms may be the result of RV-PA conduit stenosis, the formation of subaortic obstruction, or a residual VSD [16,17,18].

2. Diagnostics, medical indications and contraindications for diagnostic methods

The diagnosis is established based on the data of:

1. Electrocardiography;

2. Transthoracic echocardiography;

3. Transvenous cardiac catheterization and angiocardiography;

4. Computed tomography of the heart and vessels with contrast or Magnetic resonance imaging of the heart with contrast.

Diagnostic criteria

Symptoms:

• dyspnea at rest or during feeding;

• cyanosis;

• poor weight gain (delayed physical development);

• frequent respiratory infections;

Anamnesis: prenatal diagnosis of congenital heart disease.

Physical examination:

• tachycardia;

• dyspnea;

• hepatomegaly;

• cyanosis of varying severity;

• murmurs of varying intensity (the presence of a systolic murmur in the 4th intercostal space along the left sternal border may be due to the presence of a VSD. A systolic-diastolic murmur in the 2nd–3rd intercostal space along the left sternal border may indicate the presence of a patent ductus arteriosus).

Laboratory tests: do not provide characteristic information for TGA.

Instrumental Studies:

ECG:

• signs of right ventricular hypertrophy with a positive T-wave in lead V_1;

• right axis deviation;

• other ventricular and supraventricular rhythm disturbances.

Echocardiography:

• atrioventricular concordance;

• ventriculoarterial discordance.

2.1 Complaints and Anamnesis

• At the diagnostic stage, it is recommended to collect medical history and complaints regarding vascular pathology in all patients (parents of patients) with suspected TGA to determine the severity of the patient's condition [14,22,29].

ESC/ESC I C (LoE 5, GoR C)

Comments: when taking the medical history and complaints, it is necessary to be aware of the presence of dyspnea at rest or during feeding, delayed physical development, susceptibility to colds, as well as the presence and severity of cyanosis.

2.2 Physical Examination

• When examining a patient with suspected TGA, it is recommended to focus on heart auscultation, femoral artery pulsation, heart and respiratory rate, and liver size assessment to determine the severity of the condition and identify signs of circulatory failure [14, 22, 29].

ESC/ESC I C (LoE 5, GoR C)

Comments: A systolic murmur at the 4th intercostal space along the left sternal border may be caused by a VSD. A systolic-diastolic murmur at the 2nd–3rd intercostal space along the left sternal border may indicate a patent ductus arteriosus (PDA). Absence or weakening of femoral artery pulsation may indicate coarctation of the aorta.

• During the physical examination of adult patients after atrial switch, it is recommended to check for signs of venous congestion, such as head and neck edema, lower extremity edema, and hepatomegaly [22].

ESC/ESC I C (LoE 5, GoR C)

Comments: Head and neck edema may be a clinical manifestation of blood flow obstruction at the level of the upper segment of the systemic venous baffle; lower extremity edema and hepatomegaly, at the level of the lower segment of the systemic venous baffle.

2.3 Laboratory Diagnostics

• All patients with TGA admitted to the hospital are recommended to undergo acid-base balance and blood gas analysis (pH, BE, pCO2, PO2, Lac — capillary/arterial/venous blood samples) to assess the severity of hypoxemia and the degree of metabolic disorders [14, 22, 29].

ESC/ESC I C (LoE 5, GoR C)

ESC/ESC I C (LoE 5, GoR C)

• All patients with TGA are recommended to undergo a complete blood count (CBC) and urinalysis, including assessment of hemoglobin and hematocrit levels, red blood cell, leukocyte, and platelet counts, and erythrocyte sedimentation rate (ESR) as part of the initial evaluation upon hospital admission, including for surgical treatment, during follow-up at least once a year, and in the postoperative period if necessary [22, 35].

ESC/ESC I C (LoE 5, GoR C)

Comments: Performing a complete blood count in all patients with TGA during dispensary follow-up and prior to surgical treatment is important for detecting anemia and timely correction thereof. In patients with a mean corpuscular volume (MCV) of less than 80 fL, it is advisable to determine serum iron, ferritin, transferrin, and total iron-binding capacity (TIBC) to timely correct iron deficiency states. In patients with a mean corpuscular volume of more than 100 fL, it is advisable to determine blood vitamin B12 (cyanocobalamin) and serum folic acid levels to timely correct vitamin B12 or folate deficiency states. The above conditions can negatively affect the clinical and functional status and the course of the disease, as well as the outcomes of surgical treatment [22]. In addition, during dispensary follow-up and before surgical treatment, a urinalysis must also be performed to rule out urogenital infections and kidney disease.

ESC/ESC I C (LoE 5, GoR C)

Comments: Increased clearance of red blood cells and hemoglobin and impaired uric acid excretion can lead to hyperuricemia with a potential risk of gout [22]. In the presence of severe renal and hepatic failure, therapy aimed at normalizing their function is administered. Once the parameters have normalized, the patient's readiness for surgery is evaluated.

ESC/ESC I C (LoE 5, GoR C)

ESC/ESC I C (LoE 5, GoR C)

• In patients with TGA during follow-up, it is recommended to monitor blood levels of B-type natriuretic peptide or N-terminal pro-B-type natriuretic peptide (NT-proBNP) for mortality risk stratification, as well as in the case of surgical treatment if necessary in the pre- and/or postoperative period [26, 27, 113].

ESC/ACC IIa C (LOE 4, GoR C)

Comments: monitoring NT-proBNP levels is useful for assessing the risk of congestive heart failure and adverse outcomes.

2.4 Instrumental Diagnostics

• All patients with suspected TGA are recommended to undergo pulse oximetry to assess the severity of arterial hypoxemia [14, 22, 29].

ESC/ESC I C (LoE 5, GoR C)

Comments: the measurement is performed on the right arm.

• All patients with suspected TGA are recommended to undergo blood pressure measurement on peripheral arteries (arms and legs) to rule out coarctation of the aorta [14, 22].

ESC/ESC I C (LoE 5, GoR C)

Comments: the measurement is performed on the right arm and either leg to determine the blood pressure gradient as a sign of aortic coarctation.

• All patients with TGA are recommended to undergo an electrocardiogram (ECG) to diagnose rhythm and conduction disorders [14, 22, 29].

ESC/ESC I C (LoE 5, GoR C)

Comments: Frequently, newborns with TGA have normal ECG parameters. Later, signs of right ventricular hypertrophy appear with a positive T wave in lead V₁ and right axis deviation.

• All patients with suspected TGA are recommended to undergo transthoracic echocardiography (TTE) combined with color Doppler mapping to establish the diagnosis, assess defect morphology, and determine treatment strategy (see Appendix A3) [14, 22, 29].

ESC/ESC I C (LoE 5, GoR C)

Comments: During transthoracic echocardiography, it is necessary to:

1) determine atrioventricular concordance;

2) verify the great arteries: visualize the bifurcation of the pulmonary artery branches and (if possible) the coronary artery ostia;

3) determine the spatial relationship of the great arteries at the valve level in the short-axis view: the aorta positioned anteriorly and to the right of the pulmonary artery (PA); the aorta positioned to the right and adjacent to the PA in a "side-by-side" fashion;

4) assess the size of the atrial septal defect (ASD, patent foramen ovale) and the presence of a ventricular septal defect (VSD), including its size and localization. Determine the "restrictiveness" of the atrial septal defect by measuring the size of the interatrial communication and the mean pressure gradient (greater than 6 mm Hg);

5) rule out atrioventricular valve anomalies;

6) assess coronary artery anatomy;

7) assess the size/volume of the left and right ventricles (LV and RV), LV myocardial thickness (inferolateral wall), and indexed LV myocardial mass.

• Transesophageal echocardiography is recommended for patients in whom transthoracic echocardiographic data are technically limited or inconclusive (see Appendix A3) [22, 29].

ESC/ACC IIa C (LOE 5, GoR C)

Comments: Echocardiography is the imaging modality of choice in children with TGA, and currently, the majority of patients are referred for cardiac surgery based solely on the echocardiographic diagnosis. A segmental approach to anatomical diagnosis provides the best framework for a comprehensive assessment of the heart defect and associated anomalies. The data obtained allow for the most precise tailoring of patient management tactics in each specific case. If the child is agitated, transthoracic echocardiography is performed under sedation. When the study is performed in an inpatient setting, echocardiography is conducted in the presence of a cardiovascular surgeon and a cardiologist for a multidisciplinary discussion of the findings.

• In patients with TGA prior to surgical treatment, transvenous cardiac catheterization and cardiac ventriculography with panaortography are recommended to verify the diagnosis in cases of complex defect anatomy or to assess the severity of pulmonary hypertension in late diagnosis of the defect [14,22].

ESC/ACC IIa C (LOE 5, GoR C)

• Prior to surgical treatment, coronarography is recommended for patients with suspected coronary artery anomalies, as well as for those scheduled for aortic translocation or an arterial switch operation [14,22].

ESC/ESC I C (LoE 5, GoR C)

• In case of inconsistency between clinical and instrumental data or difficulty in clarifying the defect anatomy at the time of diagnosis, patients with suspected TGA are recommended to undergo contrast-enhanced cardiac magnetic resonance imaging (MRI) or contrast-enhanced computed tomography of the heart and great vessels to clarify the anatomy of the defect (as well as to detect signs of shunting or blood flow obstruction at the level of the atrial venous pathway or to assess left ventricular myocardial mass in late diagnosis of congenital heart disease) [14,22].

ESC/ACC IIa C (LOE 5, GoR C)

2.5 Other Procedures

• Adult patients with TGA are recommended to undergo cardiopulmonary exercise testing (cardiopulmonary exercise testing/ ergospirometry) at least once every three years to assess left ventricular functional reserve [37].

ESC/ESC I C (LoE 5, GoR C)

Comments: spiroergometry testing in patients allows for the determination of peak oxygen consumption (VO2) in order to predict the development of myocardial dysfunction.

Patients with low cardiac output, as well as those who have suffered a myocardial infarction or present with effort angina (coronary blood flow impairment) following an arterial switch operation, are individually indicated for myocardial scintigraphy and/or myocardial scintigraphy with functional tests.

In addition, patients may individually (rarely) undergo myocardial biopsy to rule out inflammatory myocardial diseases, dilated and restrictive cardiomyopathies, and to study the morphological substrate of ventricular rhythm disorders in the pre- and postoperative periods in patients with TGA.

3. Treatment, including drug and non-drug therapies, diet therapy, and pain management

3.1 Conservative Treatment

• All newborns with TGA, immediately after venous access is established, are recommended to start an infusion of a prostaglandin preparation (Alprostadil**) [37].

ESC/ESC I C (LoE 5, GoR C)

Comments: continuous infusion of the drug is used at a dose of 0.01-0.1 mcg/kg/min IV. The infusion rate can be slowly increased to the minimum effective dose (but not exceeding 0.1 mcg/kg/min) [82,91-92]. Infusion of the C01EA prostaglandin group drug is continued until surgery.

• In the case of a restrictive patent ductus arteriosus (according to Echocardiography, with decreased saturation, lactacidosis), all newborns with "simple TGA" are recommended an increased dose of prostaglandins (but not exceeding 0.1 mcg/kg/min) [15,37,82,91-92].

No ESC guideline (LoE 5, GoR C)

Comments: Doses above 0.05 mcg/kg/min require transferring the child to the intensive care unit and, if necessary (in the presence of respiratory disorders), placing the patient on mechanical ventilation. Doses exceeding 0.1 mcg/kg/min are inappropriate to use [37,91,92].

• Neonates with TGA and risk factors for infection (amniotic fluid aspiration, presence of an umbilical venous catheter or central venous catheter) are recommended systemic antibacterial drugs in age-appropriate doses in the maternity hospital, continuing their administration for 48–72 hours to improve the outcomes of subsequent surgical correction of the defect [36].

No ESC guideline (LoE 5, GoR C)

• In case of suspected (severe metabolic disorders and low saturation levels) or ultrasound-confirmed restrictive atrial communication in a newborn with TGA, it is recommended to transfer the patient to mechanical ventilation, increase the dose of the prostaglandin preparation, administer muscle relaxants in calculated doses, and initiate additional oxygen insufflation in the inspired gas mixture for potential condition stabilization followed by subsequent surgical correction of congenital heart disease [15,37,91,92].

No ESC guideline (LoE 5, GoR C)

• Adult patients with systemic RV systolic dysfunction and TGA are not recommended to use ACE inhibitors, beta-blockers, angiotensin II receptor antagonists, or aldosterone antagonists as monotherapy or in combination to improve prognosis [45].

ESC/RSC III C (LoE 2, GoR A)

Comments: currently, there are no data confirming the efficacy of this pharmacotherapy in patients with systemic RV systolic dysfunction. However, prescribing the above classes of drugs according to indications is possible in the presence of comorbid pathology, including standard heart failure treatment, weighing the potential benefits against the risks of decreased cardiac output and systemic hypotension development.

The administration of antiarrhythmic drugs, especially in patients after atrial switch procedures, should be carried out with extreme caution due to the frequent development of bradycardia.

In case of heart failure decompensation, diuretics can be added to the therapy for symptom relief.

3.2 Surgical Treatment

Palliative treatment

• Neonates with TGA and an intact ventricular septum are recommended to undergo balloon atrial septostomy in the first days of life in a perinatal or cardiac surgery center to prevent the development of restriction at the atrial communication and a sharp deterioration in the newborn's condition [14,29].

ESC/RSC IIa C (LoE 5, GoR C)

Comments: furthermore, increasing arterial saturation provides flexibility in choosing the timing of surgery within 1-3 weeks after birth. In cases where the patient has an ASD of adequate size, correction of the defect can be performed without prior transvenous cardiac catheterization and atrial septostomy.

• Neonates with TGA and a high degree of restriction of the atrial communication (pressure gradient greater than 6 mmHg, severe metabolic disorders, and low saturation levels) are recommended to undergo urgent balloon atrial septostomy for stabilization [14].

No ESC guideline (LoE 5, GoR C)

Radical single-stage correction of "simple" TGA

• Neonates with TGA and IVSD are recommended to undergo an arterial switch operation in the first 2-4 weeks of life for radical correction of the defect [6, 46].

ESC/RSC I B (LoE 5, GoR C)

Comments: The operation is performed in the neonatal period, before the left ventricle has lost its ability to maintain systemic circulation. Left ventricular involution may be delayed due to the persistence of a large PDA or the presence of dynamic left ventricular outflow tract obstruction.

• In case of unfavorable coronary artery anatomy, it is recommended to perform either an arterial switch operation (given sufficient experience with such interventions) or an atrial switch procedure (correction of transposition of the great arteries) [14,40].

No ESC guideline (LoE 5, GoR C)

Comments: There are variants where the right coronary artery arises from the posterior sinus, or the right coronary artery arises from the posterior sinus with simultaneous independent origin of the left anterior descending branch from the left sinus. There is also an anatomical variant characterized by a single coronary artery arising from the right adjacent sinus and running posteriorly toward the pulmonary trunk, or arising from the left adjacent sinus and running anteriorly toward the right ventricular outflow tract. In rare cases, both main arteries originate from a single adjacent sinus, usually the right, and one or both arteries run intramurally, creating the impression that they arise from different sinuses. Other rare variants may also occur, increasing the risk of primary radical intervention in TGA

Coronary artery variants affect the planning and execution of the arterial switch operation, as difficulties may arise in transferring the coronary ostia to the neoaorta.

• Preventive prolonged sternotomy is recommended for newborn patients requiring high doses of cardiotonic support with hemodynamic instability or at high risk of developing tight mediastinum syndrome (assuming/observing significant ventricular myocardial edema) [14,37].

No ESC guideline (LoE 5, GoR C)

Two-stage surgical treatment of "simple" TGA

If the optimal time window for performing the arterial switch operation has been missed, a staged treatment approach is performed. To select a staged treatment approach, where the first stage involves pulmonary artery banding and creation of a systemic-pulmonary shunt, the following indicators are required:

1) age over 1-2 months,

2) left ventricular mass to right ventricular mass ratio <0.6 or left ventricular pressure <50 mm Hg.

Additional useful, but non-decisive criteria are echocardiographic parameters– presence or absence of interventricular septum bulging into the left ventricular cavity, wall thickness, and ventricular volume.

• If a primary arterial switch operation is not feasible in patients with TGA, it is recommended to perform pulmonary artery banding with creation of a systemic-pulmonary shunt (with or without) as the first stage, followed by the arterial switch operation (arterial switch) as the second stage (at 4-6 months) [14,40].

ESC/ROS IIa C (LOE 5, GOR C)

Comments: Dynamic left ventricular outflow tract obstruction is not a contraindication to performing an arterial switch operation. This type of obstruction resolves spontaneously after surgery. Mild anatomical valvular or subvalvular pulmonary stenosis is relieved during the arterial switch operation without increasing surgical risk.

Surgical correction of TGA with ventricular septal defect

• In patients with TGA and a restrictive VSD, it is recommended to apply the same management strategy as for "simple" TGA [47].

No ESC guideline (LoE 5, GoR C)

• In patients with TGA and a large VSD, it is recommended to perform an arterial switch operation with simultaneous closure of the septal defect without prior pulmonary artery banding at the age of 2 weeks to 2 months [47].

ESC none (LOE 5, GOR C)

• In patients with TGA and multiple VSDs (single ventricle heart variant), it is recommended to perform pulmonary artery banding as the first stage, followed by creation of a cavopulmonary anastomosis (and subsequent Fontan procedure) [47].

ESC none (LOE 5, GOR C)

• In patients with TGA with a large VSD and a hypoplastic right ventricle or an "overriding" AV valve (single ventricle heart variant), pulmonary artery banding is recommended followed by staged hemodynamic repair of the defect at a later age [46,47].

No ESC guideline (LoE 5, GoR C)

• In patients with TGA, a large VSD, and concomitant mild subaortic stenosis, it is recommended to perform an arterial switch operation with VSD repair and resection of subvalvular obstruction elements (excavation of LV membrane, excision of heart muscle tissue) [6,14,41,47].

ESC/ACC IIa C (LOE 5, GoR C)

Surgical correction of TGA with left ventricular outflow tract hypoplasia

• In patients with TGA with concomitant diffuse hypoplasia of the right ventricular outflow tract and aortic valve annulus, it is recommended to perform a Damus-Kaye-Stansel procedure combined with a Rastelli procedure at the age of 1-2 years (using an animal-derived cardiovascular patch*** or a synthetic cardiovascular patch***) [47].

ESC none (LOE 5, GOR C)

Surgical correction of TGA with aortic arch hypoplasia and/or coarctation

• In patients with TGA and concomitant aortic arch hypoplasia and/or coarctation, it is recommended to perform simultaneous aortic reconstruction and an arterial switch operation [6,32,33,34,47,49].

ESC/ROS IIa B (LOE 4, GOR C)

• In patients with TGA and concomitant aortic arch hypoplasia and/or coarctation and lack of experience in single-stage repairs, it is recommended to use a two-stage approach with relief of the aortic arch obstruction and pulmonary artery banding at the first stage and an arterial switch at the second [14,40].

No ESC guideline (LoE 5, GoR C)

Comments: There are two approaches to the surgical management of patients with concomitant aortic arch hypoplasia and coarctation. In the staged approach, aortic arch obstruction is relieved at the first stage via a left thoracotomy, accompanied by pulmonary artery banding. Intracardiac repair is deferred for several months. With the two-stage approach, overall mortality ranges from 31 to 64%.

Recently, there has been a trend toward single-stage anatomical correction of TGA with aortic arch/isthmus obstruction. Despite the complexity of the surgery and the age of the children at the time of correction, overall mortality proved to be lower [30,32,49].

Treatment of children older than 1 month with transposition of the great arteries without left ventricular outflow tract obstruction

• An atrial switch operation is recommended for patients in whom [6,13,46]:

1) the arterial switch operation was not performed in the neonatal period due to concomitant extracardiac pathology or late presentation to the clinic, when the left ventricle is no longer able to support systemic function;

ESC/RSC I B (LoE 5, GoR C)

2) the defect anatomy is unfavorable for biventricular repair.

ESC/ROS I C (LOE 5, GOR C)

Comments: Coronary artery anatomy influences the planning and execution of the arterial switch operation, as difficulties in transferring the coronary ostia to the neoaorta may arise. Unfavorable defect anatomy also includes the presence of severe pulmonary stenosis. The optimal intervention in this case is the Senning procedure and surgical relief of the stenosis at 3-6 months of age.

• An arterial switch operation is recommended for patients with a "trained" left ventricle (optionally in the presence of a VSD or after pulmonary artery banding) capable of supporting systemic function, provided there are no other contraindications to surgery [14,37].

ESC/ESC I C (LoE 5, GoR C)

Comments: To train the left ventricle, pulmonary artery banding is indicated to increase left ventricular afterload and induce hypertrophy, which will subsequently allow an arterial switch operation to be performed.

Treatment of children older than 1 month with transposition of the great arteries, ventricular septal defect, and left ventricular outflow tract obstruction

Ideal candidates for the Rastelli procedure are considered to be patients with a functionally incompetent pulmonary valve, a VSD whose upper edge is in close proximity to the aortic orifice, the ratio of its diameter to that of the descending aorta is 0.5 or greater, and the cross-sectional area of the ventricular septal defect is greater than 0.8 cm²/m², provided there is no chordal-papillary attachment of the AV valves on the surface of the infundibular septum [43]. The presence of anomalous tricuspid valve attachment to the infundibular septum in patients with TGA is not an absolute contraindication to the Rastelli procedure.

The choice of conduit type depends largely on the surgeon, but in young children it is recommended to avoid xenopericardial grafts and aortic allografts, favoring a pulmonary allograft [19].

Performing an atrial switch operation in this group of patients is associated with a high risk of postoperative complications and adverse outcomes [48].

• Reconstruction of the right ventricular outflow tract to the pulmonary arteries is recommended to be performed without the use of an artificial pulmonary trunk whenever possible; otherwise, a conduit with a competent valve is used [6,19].

ESC/ACC IIa C (LOE 4, GoR C)

• When choosing the conduit size in young children, it is recommended to take into account that outgrowing it is not the main cause of its dysfunction [42].

ESC/ROS IIa C (LOE 5, GOR C)

Comments: When reconstructing the ventricular outflow tracts, it is recommended to choose methods and technical techniques that restore their geometry to as close to natural as possible (resection/mobilization of the infundibular septum, translocation of the great arteries with subsequent orthotopic reimplantation, orthotopic implantation of an artificial pulmonary trunk, etc.) [19].

Exceeding the conduit diameter by more than 2 standard deviations from the normal mean is not advisable.

• In patients with TGA in whom surgical interventions do not involve the use of an artificial pulmonary trunk, it is recommended to perform these techniques under the age of 1 year, as these techniques promote adequate growth of the anastomosis between the right ventricle and the pulmonary trunk with a minimal risk of subsequent stenosis [14,41].

No ESC guideline (LoE 5, GoR C)

• In patients with TGA who have an indication for a Rastelli procedure, it is recommended to perform it at the age of 1-3 years [14,41].

ESC none (LOE 5, GOR C)

• Preservation of the infundibular septum during the Rastelli procedure is not recommended because it serves as a substrate for left ventricular outflow tract obstruction postoperatively [6,48].

ESC/ACC III C (LE 4, GR C)

• Ligation of the pulmonary trunk during the Rastelli procedure is not recommended as it is an unreliable method for eliminating the natural communication between the left ventricle and the pulmonary arteries [6,48,53].

ESC/ACC III C (LE 4, GR C)

• Separation of the left ventricle and pulmonary arteries during the Rastelli procedure is recommended by transection and closure of the pulmonary trunk, as this technique completely prevents its recanalization in the postoperative period [53].

No ESC guideline (LoE 5, GoR C)

• In patients with a dysplastic, functionally incompetent pulmonary valve, as an alternative to the Rastelli procedure, it is recommended to perform the REV procedure (réparation à l'étage ventriculaire – a surgical correction method for D-TGA combined with resection of pulmonary stenosis according to the original technique) [19,20].

ESC none (LE 4, GR C)

Comments: The REV procedure is an alternative method for correcting TGA with VSD and pulmonary stenosis, which avoids the use of conduits (this procedure was described in 1982).

• In cases where anatomy is unfavorable for performing the intracardiac stage of the Rastelli and REV procedures (restrictive (VSD/Ao <0.5) and/or remote VSD from the aorta; presence of chordal-papillary apparatus of AV valves on the surface of the infundibular septum; moderate right ventricular hypoplasia provided there are no coronary anomalies, particularly a single coronary artery, type I), it is recommended to perform the Bex-Nikaidoh procedure or univentricular palliation depending on the center's experience [44].

ESC/ACC IIa C (LOE 4, GoR C)

• In patients with outflow obstruction who have a pulmonary valve capable of adequate function but unsuitable as an aortic valve (provided there are no coronary anomalies such as the right coronary artery originating from sinus 2, or the left anterior descending artery originating from sinus 1), it is recommended to perform the arterial switch operation [21,23-25,28].

ESC/ACC IIa C (LE 4, GR C)

Comments: In the presence of coronary anomalies, preference is given to the REV procedure with pulmonary root translocation.

In Type G according to Yacoub and Radley-Smith, where the circumflex artery originates from the right posterior sinus and passes posterior to the pulmonary trunk, the site of coronary reimplantation onto the pulmonary trunk is shifted cranially to avoid kinking of the circumflex artery. The 'trapdoor' technique, described back in 1988, serves the same purpose. The undoubted benefit of this technique is somewhat diminished by the potential for plication of the neo-aortic bulges containing the coronary ostia after anastomosing the distal aorta with the neo-aorta.

To enlarge the lumen of the reimplanted coronary arteries, an additional autologous pericardial patch is used. However, this method is fraught with complications such as thrombosis, lack of growth, and degeneration, and therefore cannot be considered ideal.

Yamagishi et al. proposed a method of coronary translocation that is a further refinement of the 'trapdoor' technique and its subsequent modification.

Surgical treatment of complications

• In patients with life-threatening complications in the pre- and postoperative periods in the form of hemo- and hydropericardium with the potential development of cardiac tamponade, it is recommended to perform pericardiocentesis with drainage of the pericardial cavity on an emergency basis [14,37].

ESC/ACC IIa C (LOE 5, GoR C)

Comments: After draining the fluid from the pericardial cavity, it is advisable to leave a drainage system in place until fluid output ceases [14,37].

• In patients with TGA who develop rhythm disturbances, specifically complete heart block, it is recommended to implant a permanent pacemaker (single-chamber rate-responsive implantable pacemaker*** or dual-chamber rate-responsive implantable pacemaker***) [14,37].

ESC/ACC I C (LE 5, GR C)

Comments: In patients with a pacemaker implanted in early childhood, as the child grows, it is necessary to replace the epicardial lead system as well as the pacemaker itself when the battery reaches the end of its service life. This involves revision of the pacemaker and lead system, and replacement or removal of the device.

If a patient with a permanent implanted pacemaker (single-chamber rate-responsive implantable pacemaker***) develops inflammatory complications in the pacemaker pocket and/or lead system in the postoperative period, surgical revision and pacemaker explantation with placement of temporary leads are required.

• In adult patients with life-threatening arrhythmias following surgical correction of TGA, as well as those at high risk for ventricular fibrillation, it is recommended to implant an implantable cardioverter-defibrillator (dual-chamber implantable cardioverter-defibrillator*** and endocardial defibrillation lead***; if unavailable – single-chamber implantable cardioverter-defibrillator*** and endocardial defibrillation lead***) [14,37].

ESC/ACC I C (LE 5, GR C)

• In adult patients after atrial switch with severe regurgitation at the systemic (tricuspid) atrioventricular valve without significant ventricular systolic dysfunction (EF >40%), it is recommended to perform tricuspid valve repair under cardiopulmonary bypass or valve replacement (tricuspid valve replacement and aortic valve repair under cardiopulmonary bypass) regardless of clinical manifestations [22].

ESC/ACC IIa C (LOE 5, GoR C)

• Surgical treatment to eliminate abnormal blood shunting at the level of the systemic venous baffle, baffle stenosis, or pulmonary venous obstruction is recommended for adult patients after atrial switch when clinical symptoms appear [22].

ESC/ESC I C (LoE 5, GoR C)

• In patients with clinical manifestations of obstructive coronary disease, it is recommended to perform surgical treatment depending on the substrate (vessel repair, coronary artery stenting, coronary balloon angioplasty, coronary artery bypass grafting under cardiopulmonary bypass, or off-pump coronary artery bypass grafting) [22].

ESC/ESC I C (LoE 5, GoR C)

• In patients postoperatively with clinical symptoms of a residual left-to-right shunt at the ventricular septal level or significant LV volume overload, it is recommended to perform transcatheter closure of the septal defect using an occluder (cardiac occluder***) [14,22,37].

ESC/ESC I C (LoE 5, GoR C)

• In adult patients with neo-aortic root dilation >55 mm, it is recommended to perform surgical treatment (aortic resection with replacement, aortic valve replacement under cardiopulmonary bypass) [22].

ESC/ACC IIa C (LOE 5, GoR C)

• In patients with pulmonary artery branch stenosis, it is recommended to perform surgical treatment (transluminal pulmonary balloon angioplasty and/or pulmonary artery stenting, or vessel repair) regardless of clinical manifestations if a narrowing >50%, right ventricular systolic pressure >50 mmHg, and/or reduced pulmonary perfusion are detected [22].

ESC/ACC IIa C (LOE 5, GoR C)

Comments: supravalvar pulmonary stenosis and stenosis of its branches (both unilateral and bilateral) may be a consequence of the Lecompte maneuver, which must be taken into account in adult patients.

• In adult patients after the Rastelli procedure with clinical symptoms (at rest or during exertion) and a mean gradient ≥40 mmHg or severe aortic regurgitation, it is recommended to surgically relieve subaortic obstruction or regurgitation (resection of hypertrophied muscle tissue in the obstruction zone from the infundibular part of the right ventricle or resection of muscle tissue in the hypertrophy zone in combined outflow tract obstruction of both ventricles) [14,22,37].

ESC/ESC I C (LoE 5, GoR C)

• In asymptomatic adult patients after the Rastelli procedure with severe right ventricular outflow tract obstruction and/or severe pulmonary regurgitation, it is recommended to consider surgical treatment (resection of hypertrophied muscle tissue in the obstruction zone from the infundibular part of the right ventricle or resection of muscle tissue in the hypertrophy zone in combined outflow tract obstruction of both ventricles) if at least one criterion is met [22]:

a) decreased exercise tolerance (cardiopulmonary exercise testing)

b) progressive RV dilation (indexed RV end-systolic volume ≥80 mL/m2, and/or indexed RV end-diastolic volume ≥160 mL/m2, or progression of tricuspid regurgitation)

c) progressive RV systolic dysfunction

d) RV systolic pressure >80 mmHg

ESC IIb C (LoE 5, GoR C)

• For adult patients with severe neo-aortic valve regurgitation in the presence of severe comorbidities and high risk of open valve replacement, transcatheter aortic valve implantation (cardiac aortic valve bioprosthesis***) may be recommended [14,37].

ESC/RSC IIa C (LoE 5, GoR C)

3.3 Other Treatment

No.

4. Medical Rehabilitation and Sanatorium-Resort Treatment

Not addressed by ESC (LoE 4, GoR C)

Comment: since children with TGA currently have good long-term survival after surgical treatment, improving their quality of life is becoming increasingly important. Health (emotional, behavioral, and social) and deficits in any of these components can affect the ability to fulfill important social roles in the future [83].

It has been established that patients with surgically treated TGA have a somewhat reduced exercise tolerance [84]. Certain predictors of poor functional capacity include: VSD closure, decreased left ventricular function [85].

Studies have also shown that patients who have undergone surgical correction of TGA are more likely to have neurodevelopmental disorders. One center reported that 65% of adolescents who had TGA in infancy required special education services [56]. Patients with surgically repaired TGA are more likely to suffer from attention deficit/hyperactivity disorder, so it is important that children who have undergone corrective surgery for TGA undergo ongoing screening and referral to specialists for neurodevelopmental disorders [56].

Not addressed by ESC (LoE 3, GoR C)

Comment: it has been established that additional attention should be paid to the follow-up of children with "simple TGA," especially regarding sports participation [86]. Children after surgical correction of TGA should be encouraged to full activity in daily life, but isometric or prolonged exercise should be avoided. Children can participate in physical activities, including low-to-moderate dynamic or static sports [71]. However, the demand for physical activity in children with TGA tends to be reduced, which is partly due to parental overprotection [87]. Rehabilitation programs can be useful for increasing physical activity levels aimed at improving exercise tolerance and motor function in children after surgical correction of TGA.

• Within 6 months after anatomical correction of TGA under cardiopulmonary bypass, a patient with a complicated postoperative course (residual pulmonary hypertension, heart failure, infectious complications, repeated surgical interventions during a single hospitalization) is recommended to undergo rehabilitation in a specialized cardiological sanatorium-resort facility [62,64,68,75,88].

No ESC guideline (LoE 5, GoR C)

• For children with TGA undergoing staged surgical treatment, it is recommended to provide inpatient or outpatient follow-up at their place of residence with an appointment (examination, consultation) by a pediatric cardiologist/pediatrician at least once every 7 days [6].

No ESC guideline (LoE 5, GoR C)

• For patients with TGA at the stage of surgical correction, it is recommended to select individualized therapy aimed at correcting circulatory failure and reducing pulmonary vascular resistance in age-appropriate dosages (diuretics, ACE inhibitors, type 5 phosphodiesterase inhibitors) [55].

No ESC guideline (LoE 5, GoR C)

Sanatorium and spa treatment

• The third (outpatient) stage of medical rehabilitation for children after surgical correction of TGA is recommended to be carried out in sanatorium-resort settings by a multidisciplinary rehabilitation team (ICF), primarily pediatric cardiology specialists [57,93-105].

No ESC guideline (LoE 5, GoR C)

Comments: Sanatorium-resort treatment (SRT) includes medical care provided by medical organizations (sanatorium-resort organizations) for preventive, therapeutic, and rehabilitative purposes based on the use of natural therapeutic resources, including staying in health-improving areas and resorts [58,93-105].

Indications for referring children with congenital heart defects to sanatorium-resort treatment are formulated in the Order of the Russian Ministry of Health No. 1029n dated September 28, 2020, "On Approval of the Lists of Medical Indications and Contraindications for Sanatorium-Resort Treatment." However, children after surgical correction of TGA are not included in the list of indications for sanatorium-resort treatment [59].

• Sanatorium-resort treatment may be recommended for patients after surgical correction of TGA performed at an early age, who are in the stage of defect compensation, without hemodynamic impairment, with circulatory failure no higher than grade I [57-59,93-105].

No ESC guideline (LoE 5, GoR C)

Comment. In the rehabilitation of children with CHD (TGA), it is important to consider the presence of residual problems:

- heart failure,

- pulmonary hypertension,

- hypoxia and arterial hypoxemia syndrome,

- reduced immune reactivity,

- asthenoneurotic syndrome.

Contraindications for referring children who have undergone surgery for TGA to sanatorium-resort treatment include:

- circulatory failure stage IIA or more (higher than functional class II according to ROSS),

- moderate and severe pulmonary arterial hypertension (with mPAP >35 mmHg),

- life-threatening tachyarrhythmias and bradyarrhythmias,

- ventricular or atrial tachycardias,

- second- and third-degree AV blocks,

- decreased left ventricular ejection fraction,

- subacute myocarditis, pericarditis,

- presence of a pacemaker.

General contraindications for sanatorium-resort treatment and acute or subacute stage diseases, including acute infectious diseases until the isolation period ends, are also taken into account [59,93-105].

Sanatorium-resort institutions under the jurisdiction of the Russian Ministry of Health admit children aged 4 to 14 years inclusive, including accompanied by a legal representative, and children aged 15 to 18 years unaccompanied.

If the sanatorium-resort institution has a cardiology department, children aged 7 to 14 years inclusive are admitted without being accompanied by a legal representative, unless the need for accompaniment is dictated by medical indications [60,93-105].

Referral for sanatorium-resort treatment of children is performed no earlier than 6 months after surgical treatment. The duration of sanatorium-resort treatment is 21 days.

Sanatorium treatment of children after TGA correction can be carried out in the resorts of: Kislovodsk, Pyatigorsk, Gelendzhik, Sochi, Belokurikha, Yevpatoria [61,65,66].

To assess the initial clinical and functional status of patients with TGA upon admission to sanatorium-resort treatment, it is necessary to have ECG and echocardiography data, and for children with arrhythmic syndrome, Holter monitoring data.

Objectives of sanatorium-resort treatment: improvement of the cardiovascular and respiratory systems' function, as well as the child's adaptive and compensatory mechanisms, enhancement of immunological reactivity, nonspecific resistance, and the child's body defense mechanisms, reduction of muscle deconditioning, and correction of the child's psycho-emotional state [63,67,68].

Sanatorium-resort treatment of children who have undergone TGA correction includes:

1. climatic regimen appropriate to the season of the year and the patient's clinical and functional status;

2. therapeutic nutrition;

3. adequate physical activity taking into account exercise tolerance in the form of small-group or individual sessions;

4. therapeutic massage of the collar zone;

5. physical treatment methods and hardware physiotherapy (prescribed according to standard methods): antihypoxic, sedative, immunostimulatory, cardiotonic, vasodilating, antiarrhythmic, and autonomic-correcting methods;

6. psychotherapy (individual, small-group, family sessions) [61–64].

• Climate therapy (air baths, sun baths, sea bathing) is recommended for children after surgical correction of TGA, in the stage of malformation compensation, without hemodynamic disturbances, with circulatory failure no higher than grade I, for the purpose of increasing nonspecific resistance and immune defense of the child's body [61, 63, 64, 75, 93–105].

No ESC guideline (LoE 5, GoR C)

Comments. Climate therapy is carried out according to standard methods and taking into account special dosimetric tables: climate therapy, – starting with regimen I (gentle, mild) for 3–5 days, then – regimen II (gentle-training);

- air baths are prescribed depending on the season of the year, the regimen in the ward (sanatorium climate ward) or in the open air, daily, for 5–30 minutes, with a course of 15–20 procedures;

- heliotherapy (sun baths) is prescribed according to regimen I (gentle, diffused solar radiation) with a dosage from 1 to 4 therapeutic doses and regimen II (gentle-training) – with an increase in therapeutic doses from (1 to 8), daily, 1–2 times a day, treatment course of 15–18 procedures;

- sea bathing (thalassotherapy) is carried out according to regimen I (gentle) and regimen II (gentle-training) (at a sea water temperature of at least 22°C). It starts with rubbing, dousing, and dipping for 2–3 days.

• At the sanatorium-resort stage, it is recommended to prescribe medical nutrition for children after surgical correction of TGA, in the stage of malformation compensation, without hemodynamic disturbances, with circulatory failure no higher than grade I [61, 62, 63, 69, 74, 93–105].

No ESC guideline (LoE 5, GoR C)

Comments: in sanatorium-resort institutions, a standard diet is used (Pevzner therapeutic diet table No. 15) without exceeding the age norm of carbohydrates, animal fats, fluids, and salt [61, 63, 69, 93–105].

• For patients after surgical correction of TGA, in the stage of malformation compensation, without hemodynamic disturbances, with circulatory failure no higher than grade I, it is recommended to prescribe a physical activity regimen [63, 70–74, 93–105].

No ESC guideline (LoE 5, GoR C)

Comments: the physical activity regimen includes:

- morning hygienic gymnastics with self-monitoring of heart rate (HR), therapeutic gymnastics;

- walks in the fresh air along the sea and in the park area;

- therapeutic dosed walking is prescribed adequately to the patient's condition at a pace of 70–80 steps per minute according to regimen I and 80–90 steps per minute according to regimen II with short-term rest (3–5 min) on a bench. Before and after therapeutic walking, the pulse rate is measured to monitor load tolerance.

For patients with TGA and circulatory failure grade _I, physical loads are prescribed according to regimen I. If a patient shows worsened tolerance to physical and emotional loads or worsened myocardial functional capacities during the sanatorium-resort stage of treatment, the child is transferred to regimen I (gentle) until the end of the sanatorium stay.

No ESC guideline (LoE 5, GoR C)

Comments: massage techniques are used – stroking, rubbing, kneading. Procedures are carried out daily, lasting 10–12 minutes, with a course of 8–10 procedures.

• At the sanatorium-resort stage, for children after surgical correction of TGA, in the stage of malformation compensation, without hemodynamic disturbances, with circulatory failure no higher than grade I, it is recommended to prescribe antihypoxic physical treatment methods that promote increased blood oxygenation, reduction of tissue hypoxia, and enhanced oxygen utilization by the myocardium and brain (therapeutic mineral baths (sodium chloride), gas baths (carbon dioxide, oxygen)) [61, 63, 93–105].

ESC none (LOE 5, GOR C)

Comment: Sodium chloride baths: water temperature 36–37°C, sodium chloride concentration 10–20 g/L, procedure duration 8–12 min, every other day, 8–10 procedures per course;

Carbon dioxide baths: water temperature – 34-36°C, CO₂ concentration – 0.6-0.9-1.3 g/L, every other day, procedure duration 6-10 min, course of 8-10 procedures;

Oxygen baths: water temperature – 36-37°C, oxygen pressure – 0.3 atm, 8-10 min prescribed every other day, course of – 8-10 procedures.

• Sedative treatment methods are recommended for children after surgical correction of TGA, in the stage of defect compensation, without hemodynamic disturbances, with circulatory failure no higher than grade I, and are aimed at enhancing inhibitory processes in the CNS (general medical massage, therapeutic aromatic baths [coniferous, iodine-bromine], gas baths [nitrogen], electrosleep) [61,63,93-105].

No ESC guideline (LoE 5, GoR C)

Comment: Coniferous baths: used in children over 6 years of age, temperature 36-37°C, every other day, 7-10 min, course of – 8-10 procedures;

Iodine-bromine baths: water temperature 36-37°C, 8-10 min (depending on age), every other day, course of 8-12 baths;

Nitrogen baths: water temperature in the bath 36°C, 8-10 min, every other day, course of 8-10 baths.

Electrosleep: performed using the orbital-occipital method with a frequency of 6-10 mA, duration 15-20 minutes, daily, course of 12-15 procedures.

• At the sanatorium-resort stage of treatment for children after surgical correction of TGA, in the compensation stage of the defect, without hemodynamic impairment, with circulatory insufficiency no higher than grade I, as a cardiotonic method it is recommended to use gas (carbon dioxide) baths aimed at stimulating cardiac activity [61-63,93-105].

ESC none (LOE 5, GOR C)

ESC none (LOE 5, GOR C)

Comments: "Dry" carbon dioxide baths: carbon dioxide concentration 32%, temperature 32°C, procedure duration – 8-20 min (depending on age), daily or every other day, course – 8-10 procedures;

SMT therapy: prescribed paravertebrally to the cervical-collar zone (C_IV-Th_II), modes IV and III, exposure frequency 30 Hz, modulation depth 50-75%, 5 min for each mode, daily, course of 10 procedures;

Galvanization of the collar region (Scherbak galvanic collar): current intensity 2-8 mA, procedure duration 8-16 min according to the schedule, daily, course of 10 procedures;

Infrared laser therapy: prescribed paravertebrally at the level of C_IV-Th_II, labile technique, frequency – 80 Hz, pulse power 2-4 W, procedure duration – 2, 3, 4 min (depending on age), daily, course of 5-6 procedures;

Circular and jet showers: water temperature 35-30°C, performed for 2-3 minutes, every other day, course of 10-15 procedures;

Contrast shower: water temperatures 36 and 18°C, performed for 8-10 min, every other day, course of 8-10 procedures.

ESC none (LOE 5, GOR C)

Comment: therapeutic swimming is performed in the warm water of an open water body or swimming pool at a comfortable pace with a gradual increase in distance and duration of stay in the water.

• Psychotherapy is recommended for patients after surgical correction of TGA, in the stage of defect compensation, without hemodynamic disturbances, with circulatory failure no higher than grade I in the form of individual, small-group, and family sessions to correct the child's relationships with the surrounding social environment, eliminate negative psychoemotional factors, and form an adequate response to stressful situations [63,76,93-105].

ESC none (LOE 5, GOR C)

Comment: if the clinical and functional state of patients with TGA deteriorates during the sanatorium-resort stage of treatment, emergency professional care is required along with further management of the child on baseline pharmacotherapy, sparing climate-physical and therapeutic regimens.

5. Prevention and Dispensary Observation

• All patients after surgical correction of TGA are recommended lifelong follow-up and management by a specialist (appointment/examination/consultation with a pediatric cardiologist, appointment/examination/consultation with a cardiologist) for the timely detection and management of potential postoperative complications [6,14,22].

ESC/ESC I C (LoE 5, GoR C)

Comments: The frequency of follow-up depends on age, type of surgical procedure performed, and hemodynamic status.

• Regardless of the type of surgical correction performed, all patients with TGA are recommended follow-up and consultations with a cardiologist at a specialized center competent in the care of adult patients with congenital heart disease at least once a year [22].

ESC/ESC I C (LoE 5, GoR C)

Comments: Long-term complications of the arterial switch operation:

1) coronary artery occlusion or stenosis; 2) supravalvular pulmonary stenosis; 3) aortic regurgitation; 4) aortic root dilation; 5) residual VSD; 6) ventricular outflow tract obstruction.

Long-term complications of the atrial switch operation: 1) systemic right ventricular dysfunction; 2) tricuspid regurgitation; 3) left ventricular outflow obstruction; 4) systemic or pulmonary venous return obstruction; 5) intra-atrial shunts; 6) arrhythmias (sick sinus syndrome, atrial fibrillation, atrial and ventricular tachyarrhythmias).

The frequency of dispensary appointments (examinations, consultations) with a pediatric cardiologist/cardiologist is at 1, 3, 6, and 12 months after surgery. Dispensary follow-up includes ECG and echocardiography, exercise ECG and/or exercise echocardiography, pulse oximetry, and, if necessary, Holter monitoring, cardiac CT, and/or cardiac and great vessel MRI. Subsequent patient monitoring is carried out at intervals of 3–12 months [14,39].

When determining the frequency of follow-up, one should be guided by the presence of heart failure symptoms, hemodynamic status, arrhythmias, hypoxemia, etc. Depending on these factors, all patients with congenital heart disease can be divided into four groups (A, B, C, D):

Group A

- heart failure functional class I;

- absence of anatomical hemodynamic disorders;

- absence of cardiac arrhythmias;

- normal liver, kidney, and lung function.

Group B

- heart failure functional class II;

- minimal stenosis and/or valve regurgitation (grade I), mild aortic or ventricular dilation;

- left ventricular EF at least 50%, right ventricular EF at least 40%;

- hemodynamically insignificant intracardiac shunts (Qp/Qs <1.5);

- absence of hypoxemia;

- arrhythmias not requiring treatment;

- absence of signs of pulmonary hypertension;

- normal renal and hepatic function.

Group C

- heart failure functional class III;

- moderate or significant stenosis and/or valve regurgitation (grade II–III), arterial or venous stenoses, moderate aortic or ventricular dilation;

- left ventricular EF 40–49%, right ventricular EF 35–39%;

- hemodynamically significant intracardiac shunts (Qp/Qs ≥1.5);

- moderate hypoxemia (Sat O2 ≥85%);

- arrhythmias controlled by therapy;

- pulmonary hypertension (pulmonary hypertension functional class I–II);

- internal organ dysfunction controlled by therapy.

Group D

- heart failure FC IV;

- significant aortic dilation;

- severe hypoxemia (Sat O2 <85%);

- cardiac arrhythmias refractory to therapy;

- pulmonary hypertension (pulmonary hypertension FC III–IV);

- internal organ dysfunction refractory to ongoing therapy.

Depending on the type of surgical correction of TGA performed and the presence of specific symptoms, a different follow-up frequency and scope of required examinations are determined for each patient.

Atrial switch operation

Arterial switch operation

ESC/ACC IIa C (LOE 5, GoR C)

• All patients after an arterial switch operation are recommended to undergo coronary imaging (coronary duplex scanning and/or coronary angiography and/or computed tomography coronary angiography) before participating in competitive sports [16].

ESC/RSC IIa C (LE 4, GR C)

• Adult patients after an arterial switch operation are recommended an annual evaluation including medical history, 12-lead electrocardiography, and echocardiography [37].

ESC/ESC I C (LoE 5, GoR C)

• All patients with TGA during follow-up after an arterial switch operation are recommended to undergo transthoracic echocardiography combined with color Doppler mapping at least once a year to detect potential postoperative complications [14,22,29].

ESC/ESC I C (LoE 5, GoR C)

Comments: repeat echocardiography is typically used to monitor ventricular dimensions and function, neo-aortic dimensions, and to rule out trunk (suture site) and pulmonary artery branch stenoses.

• All patients with TGA during follow-up after an atrial switch operation are recommended to undergo transthoracic echocardiography combined with color Doppler mapping at least once a year to detect potential postoperative complications [14,22,29,39].

ESC/ESC I C (LoE 5, GoR C)

Comments: Left ventricular dilation and dysfunction are important factors when deciding on surgical correction of an incompetent aortic valve. Pulmonary venous return anomalies and systemic right ventricular systolic dysfunction are ruled out, and blood flow in the pulmonary and caval tunnels is assessed.

• When evaluating adult patients after an arterial switch operation, contrast-enhanced cardiac magnetic resonance imaging is recommended for all patients every 3–5 years or on an individual basis to timely rule out the development of postoperative complications [38].

ESC/ACC IIa C (LOE 5, GoR C)

• All patients who have undergone arterial switch operations (especially patients with coronary artery anomalies) who exhibit electrocardiographic and/or echocardiographic signs of myocardial ischemia are recommended to undergo angiocardiography with coronary angiography to rule out or detect coronary blood flow disorders [14,22,78,79].

ESC/ESC I C (LoE 5, GoR C)

Comments: during coronary angiography, intravascular ultrasound (intravascular ultrasound of the vessel wall) may be performed to clarify the state of the coronary vessel wall.

• Vena cava phlebography is recommended for patients who have undergone atrial switch operations when signs of obstruction at the atrial baffle level are detected, in order to rule out or assess the degree of stenosis at the atrial baffle level [80,81].

ESC/ACC IIa C (LOE 5, GoR C)

• Adult patients with TGA are recommended to undergo Holter monitoring at least once every two years to detect potential arrhythmias [37].

ESC/ACC IIa C (LOE 5, GoR C)

• Holter monitoring, event recorder systems, and intracardiac electrophysiological studies are recommended if patients with TGA have a history of (or suspected) arrhythmias or if arrhythmias are detected on an ECG [22].

ESC/ACC IIa C (LOE 5, GoR C)

Comments: sinus node dysfunction and supraventricular tachycardia in patients after an arterial switch operation are rare, unlike in patients after an atrial switch operation.

• If arrhythmias are detected in a patient after surgical treatment of TGA and the diagnosis is uncertain, it is recommended to consider performing an electrophysiological study (EPS), specifically transesophageal atrial pacing, to clarify the form and morphology of the arrhythmia [81].

ESC/ACC IIa C (LOE 5, GoR C)

Comments: This technique allows assessment of AV conduction. In addition, incremental transesophageal pacing can be used to provoke or terminate paroxysms of AV tachycardias.

• If complications develop in the form of cardiac rhythm disturbances requiring permanent pacemaker implantation, patients with TGA are recommended to undergo follow-up every 3–6 months, and, if necessary, pacemaker parameter adjustment [80].

ESC/ACC I C (LE 5, GR C)

6. Organization of Medical Care

Indications for planned hospitalization:

1) Ineffectiveness of drug therapy at the prehospital stage;

2) Inability to provide specialized medical care and diagnostics (CT angiography, MRI, cardiac catheterization) in an outpatient setting;

3) Elective surgeries.

Indications for emergency hospitalization:

Life-threatening conditions.

Indications for patient discharge from the hospital:

1) Upon the patient's recovery;

2) Upon persistent improvement, when the patient's health status allows them to continue treatment in an outpatient clinic or at home without detriment to their health;

3) When it is necessary to transfer the patient to another healthcare organization;

4) Upon the written request of the patient or their legal representative, provided that discharge does not threaten the patient's life and is not dangerous to others.

In cases of a prenatally established diagnosis of TGA, delivery of all patients is carried out in a specialized inpatient facility equipped with a neonatal intensive care unit (NICU) and located in close transport accessibility to a cardiac surgery center. Immediately after delivery and stabilization, patients are transferred to the NICU for adequate monitoring of vital functions and further stabilization [48,54].

7. Additional Information

Prognosis of surgical treatment

Almost all patients die within the first year of life without surgical intervention. Surgical 30-day mortality after anatomical correction is approximately 5.6% (EACTS database). Risk factors include prematurity, birth weight <2.5 kg, VSD, or aortic pathology [14]. Long-term 25-year survival and freedom from arrhythmia are 97%. Most patients maintain normal ventricular systolic function and exercise tolerance. The main causes of death are sudden death and myocardial infarction. The most frequent long-term complication is neo-aortic valve regurgitation associated with root dilatation, developing in 7% of patients 10 years after the arterial switch operation and in 35% of patients 5 years after the arterial switch operation with relief of left ventricular outflow tract obstruction. Hospital mortality after atrial switch ranges from 0 to 6%, and the long-term postoperative period is characterized by severe complications such as right ventricular dysfunction, tricuspid regurgitation, and supraventricular arrhythmias. Survival at 10 and 25 years is 90% and 74%, respectively. Immediate results of the Rastelli procedure are characterized by low hospital mortality (from 0 to 7%). Long-term survival is lower than after the Mustard operation and physiological correction, and at 10 and 20 years is 93% and 57%, respectively. The main cause of death is heart failure and arrhythmias. Freedom from right ventricular outflow tract obstruction at 20 years is 32%. Encouraging intermediate results have been obtained for the REV, Bex-Nikaidoh, and truncation switch operations. Further accumulation of experience is required.

Criteria for Evaluating the Quality of Medical Care

References

Appendix A1. Working Group Composition

1. Apkhanova T.V., MD, "National Association of Experts in Spa Treatment"

2. Baryshnikova I.Yu., PhD in Medical Sciences (Moscow) All-Russian Public Organization for the Promotion of the Development of Radiation Diagnostics and Therapy "Russian Society of Roentgenologists and Radiologists"

3. Bokeria L.A., Academician of the RAS (Moscow)

4. Garmash O.I., Deputy Director for Science, State Budgetary Healthcare Institution of the Republic of Crimea "Research Institute of Children's Resortology, Physiotherapy and Medical Rehabilitation"

5. Golubova T.F., Director of the State Budgetary Healthcare Institution of the Republic of Crimea "Research Institute of Children's Resortology, Physiotherapy and Medical Rehabilitation", D.Sc. (Medicine), Professor

6. Golukhova Elena Zelikovna, Academician of the RAS, D.Sc. (Medicine), Professor (Moscow), Russian Society of Cardiology (RSC), Association of Cardiovascular Surgeons (ACVS)

7. Gulasaryan Ruben Sergeevich, Ph.D. (Medicine) (Moscow), ACVS

8. Doktorova V.P. (Moscow), ACVS

9. Eliseeva L.V., Researcher, Department of Functional Diagnostics, Clinical Physiology and Research Methods, SBIH RC "RIIDKFiMR"

10. Irtyuga Olga Borisovna, D.Sc. (Medicine) (Saint Petersburg), RSC

11. Kalashnikov S.V., Ph.D. (Medicine) (Moscow), ACVS

12. Kim Alexey Ivanovich, D.Sc. (Medicine), Professor (Moscow), RSC, ACVS

13. Kovalev I.A., DSc in Medical Sciences, "Association of Pediatric Cardiologists of Russia", (Moscow)

14. Konchugova T.V., D.Sc. (Medicine), Professor, "National Association of Experts in Sanatorium-Resort Treatment"

15. Krupyanko S.M., MD, Association of Pediatric Cardiologists of Russia, (Moscow)

16. Kurganova A.V., Head of the Department of Functional Diagnostics, Clinical Physiology and Laboratory Research Methods, SBIH RC "RIIDKFiMR", Ph.D. (Medicine)

17. Morozov Alexander Alexandrovich, D.Sc. (Medicine) (Saint Petersburg), RSC

18. Popov Alexey Evgenievich, Ph.D. (Medicine) (Kaliningrad), ACVS

19. Rychina Inna Evgenievna, Ph.D. (Medicine) (Moscow), All-Russian Public Organization for Assistance to the Development of Radiology and Therapy "Russian Society of Radiologists"

20. Trunina I.I., Doctor of Medical Sciences, "Association of Pediatric Cardiologists of Russia", (Moscow)

21. Baryshnikova I.Yu., PhD in Medical Sciences (Moscow) All-Russian Public Organization for the Promotion of the Development of Radiation Diagnostics and Therapy "Russian Society of Roentgenologists and Radiologists"

22. Sinitsyn V.E., MD, PhD, Professor (Moscow), All-Russian Public Organization for the Promotion of the Development of Diagnostic Radiology and Therapy "Russian Society of Roentgenologists and Radiologists"

23. Fesyun Anatoly Dmitrievich, MD, PhD, Associate Professor, President of the National Association of Experts in Spa Treatment and Balneology

24. Yurpolskaya L.A., Doctor of Medical Sciences (Moscow) All-Russian Public Organization for Assistance to the Development of Radiology and Therapy "Russian Society of Radiologists"

25. Yakovlev Maxim Yuryevich, MD, PhD, "National Association of Experts in Spa Treatment and Balneology"

Appendix A2. Methodology for Developing Clinical Guidelines

Target audience for these clinical guidelines:

• pediatric cardiologist;

• cardiovascular surgeon;

• pediatrician;

• neonatologist;

• cardiologist;

• ultrasound diagnostics physician;

• functional diagnostics physician;

• radiologist.

Methods used for collecting/selecting evidence: electronic database search.

Description of methods used to assess the quality and strength of evidence: the evidence base for the guidelines includes publications indexed in the PubMed and Scopus databases. The literature search depth was 30 years.

Methods used to assess the quality and strength of evidence

• expert consensus;

• evaluation of the recommendation quality in accordance with the rating scheme (Table P1).

• evaluation of the evidence strength in accordance with the rating scheme (Table P2).

During the development of the clinical guidelines, international scales for the level of recommendation consensus and the level of evidence quality were used (Tables P1 and P2), as well as a new system of LEQ and LRC scales for therapeutic, rehabilitation, preventive, and diagnostic interventions (Tables P3, P4, and P5), introduced in 2018 by the Center for Expertise and Quality Control of Medical Care of the Russian Ministry of Health. The formulation of the National Guidelines was based on ESC recommendations, taking into account national specifics, examination and treatment features, and the availability of medical care. For this reason, the text of these clinical guidelines simultaneously uses two scales for evaluating the reliability of evidence for recommendation statements: ESC levels of evidence with LRC and LEQ. ESC recommendation classes have been added to evaluate the necessity of executing a recommendation statement.

Table P1. Classes of recommendations according to the guidelines of the European Society of Cardiology (ESC).

Table P2. Levels of evidence according to the guidelines of the European Society of Cardiology (ESC).

Table P3. Scale for assessing levels of evidence (LEQ) for prevention, treatment, and rehabilitation methods (preventive, therapeutic, rehabilitation interventions)

Table P4. Scale for assessing levels of evidence (LEQ) for diagnostic methods (diagnostic interventions)

Table P5. Scale for assessing levels of recommendation consensus (LRC) for prevention, diagnostics, treatment, and rehabilitation methods (preventive, diagnostic, therapeutic, rehabilitation interventions)

Procedure for updating clinical guidelines.

The update mechanism for clinical guidelines provides for their systematic revision — at least once every three years, — as well as upon the emergence of new evidence-based data on the diagnosis, treatment, prevention, and rehabilitation of specific diseases, or in the presence of justified additions/comments to previously approved clinical guidelines, but no more frequently than once every 6 months.

Appendix A3. Reference Materials

1. On Protection of Public Health in the Russian Federation (Federal Law No. 323-FZ of November 21, 2011)

2. On Approval of the Procedure for Providing Medical Care to Patients with Cardiovascular Diseases (Order of the Ministry of Health of Russia No. 918n of November 15, 2012)

3. Order of the Ministry of Health of Russia No. 103n dated February 28, 2019 "On approval of the procedure and timeframe for the development of clinical guidelines, their revision, the standard form of clinical guidelines and requirements for their structure, composition and scientific validity of the information included in the clinical guidelines" (Registered with the Ministry of Justice of Russia on May 8, 2019, No. 54588);

4. Order of the Ministry of Health of the Russian Federation No. 203n dated May 10, 2017 "On approval of criteria for assessing the quality of medical care";

5. Order of the Ministry of Health of the Russian Federation No. 804n dated October 13, 2017 "On approval of the nomenclature of medical services";

6. Order of the Ministry of Health of Russia No. 4n dated June 6, 2012 (as amended on July 7, 2020) "On approval of the nomenclature classification of medical devices".

7. "On Approval of the Rules for Conducting X-ray Examinations" (Order of the Ministry of Health of Russia No. 560n dated June 9, 2020 (as amended on February 18, 2021))

8. "On Approval of the Rules for Conducting Ultrasound Examinations" (Order of the Ministry of Health of Russia No. 557n dated June 8, 2020).

A3.1 Transthoracic echocardiography technique

Requirements in neonates: probes with a frequency of 7.5-12 MHz, in adults – 2.5-7 MHz.

Contraindications: none.

Limitations: cases of an inadequate acoustic window

Important indicators when analyzing and interpreting the obtained images:

Performing transthoracic echocardiography

In the preoperative period

In the 4-chamber heart view, atrioventricular concordance is visualized. In the long-axis view of the LVOT from the subcostal or left parasternal approach, parallel vessel alignment is visualized, with the pulmonary artery originating from the left ventricle.

In the short-axis view at the valve level, to verify the great arteries, it is necessary to visualize the bifurcation of the pulmonary artery branches or the coronary ostia, and determine the relative position of the great arteries: the aorta is located anteriorly and to the right of the PA; the aorta is to the right and adjacent to the PA in a "side-by-side" orientation.

From the subcostal approach in the atrial long-axis view, color Doppler mapping visualizes the atrial septal defect (patent foramen ovale). The restrictiveness of the atrial septal defect is determined by measuring the size of the interatrial communication and the mean pressure gradient (greater than 6 mm Hg).

From the suprasternal or high left parasternal approaches in short-axis views, the patent ductus arteriosus (PDA) is evaluated. Obtaining an ultrasound cross-section along the left branch of the PA is considered optimal. The PDA diameter is measured in B-mode along the inner contour of the duct at its narrowest point. In the case of a "poor acoustic window", measurements are performed using color Doppler mapping. The direction of blood shunting through the PDA is also evaluated using this mode [77].

Exclusion of VSD: multi-slice analysis combined with color Doppler mapping determines the number, size, localization, and edges of the defects.

When LV outflow tract obstruction is detected, it is important to determine its origin: whether it is dynamic due to high pressure in the right ventricle and displacement of the conal septum to the left, or if there is a pathological substrate (deformation of the pulmonary valve leaflets, a membrane, anomalous chordal attachment of the mitral valve in the LV outflow tract).

Atrioventricular valve anomalies are combined with TGA and may be represented by a common atrioventricular canal, hypoplasia and/or stenosis of the atrioventricular valve, cleft mitral valve leaflet, biventricular communication, anomalous attachment of tricuspid valve cords to the conal septum or muscular septum crest. All approaches and cross-sections must be used to identify AV valve anomalies. Subcostal and apical 4-chamber views are useful for determining the biventricular nature of the AV valve. In addition to anatomical anomalies, AV valve regurgitation may be the result of ventricular dysfunction or ischemia due to severe cyanosis.

Coronary artery anatomy: evaluated using a high-frequency probe with a coronary application (if available). The high left parasternal short-axis view at the aortic valve level is used to visualize the proximal coronary arteries. The parasternal, apical, or subcostal left ventricular long-axis views can also be informative for assessing coronary anatomy. The coronary arteries must originate from the aortic sinuses facing the pulmonary valve. The absence of a bifurcation of the left main coronary artery may indicate anomalous origin of its branches, as well as a potential intramural course of the branch crossing the outflow tract.

Determination of the size/volume of the left and right ventricles, myocardial thickness of the inferolateral LV wall, and indexed LV myocardial mass.

A3.2 Definition and evaluation of data obtained during transthoracic echocardiography

During transthoracic echocardiography, it is necessary to determine and evaluate the following items:

• determine the type of intrathoracic heart position;

• evaluate the spatial relationship of the great vessels;

• determine the coronary artery anatomy;

• determine the type of atrioventricular connection;

• evaluate the anatomy and function of the heart valves;

• establish the presence or absence and the variant of the ventriculo-infundibular (mitral-semilunar) fibrous continuity;

• evaluate the distance between the tricuspid and pulmonary valves, and compare it with the aortic valve diameter;

• determine the size and position of the ventricular septal defect;

• determine the size and position of the infundibular septum, and rule out or confirm the presence of chordal-papillary attachments of the atrioventricular valves on its surface;

• evaluate the anatomy of the left ventricular outflow tract, and in case of isolated subvalvular obstruction, determine the possibility of its surgical relief;

• determine the diameter of the pulmonary valve, the morphology of its cusps, and provide an assessment regarding its functionality:

1) suitable to function as a systemic valve;

2) suitable to function as a pulmonary valve;

3) functionally unsuitable;

• evaluate the functional state of the left ventricle and provide a conclusion regarding its systemic competence based on the following parameters: end-diastolic volume index, ejection fraction, myocardial mass index, as well as the direction of ventricular septal curvature, and the pressure ratio between the left and right ventricles in the presence of a ventricular septal defect.

In the postoperative period. Following the arterial switch operation

Evaluation of ventricular size and function; neo-aortic size and function, ruling out stenosis of the trunk (at the suture line) and branches of the pulmonary artery.

Left ventricular (LV) systolic function should be evaluated by measuring the ejection fraction using the biplane Simpson's method. Evaluation of ejection fraction or fractional shortening in M-mode should be performed with caution in this patient group, particularly in the early postoperative period, because ventricular septal dyskinesia may be present, leading to an underestimation of systolic function. If LV dysfunction is suspected, a regional myocardial assessment is necessary, especially when myocardial ischemia is suspected. This assessment relies primarily on visual evaluation of regional wall motion across all LV segments using various standard LV echocardiographic views (short-axis views at different levels, apical 2-, 3-, and 4-chamber views) if other myocardial systolic function assessment techniques are unavailable. Z-scores will help to quantitatively assess LV dimensions. It is recommended to index the obtained absolute end-diastolic volume values to the patient's body surface area for better stratification of LV cavity enlargement.

Aortic root: z-scores (https://zscore.chboston.org) are used to determine aortic root dilation. Measurements of aortic root structures are taken from the left parasternal long-axis view. Mild neo-aortic valve regurgitation is a common finding in patients following an arterial switch operation. Apical 3- and 5-chamber views, as well as parasternal long- and short-axis views, allow for a comprehensive assessment of the severity of neo-aortic regurgitation. The severity of neo-aortic regurgitation is evaluated based on the vena contracta width and the degree of diastolic retrograde flow in the abdominal aorta. LV dilation and dysfunction are important factors when making decisions regarding surgical intervention for an incompetent aortic valve.

Pulmonary outflow anomalies frequently occur after the arterial switch operation and the Rastelli procedure. Following the arterial switch operation, obstruction can occur at multiple levels (supravalvular region, pulmonary artery branches). Echocardiographic grading of stenosis severity is assessed using continuous-wave Doppler (peak systolic pressure gradient across the stenosis of 17–24 mmHg is considered minor; a peak gradient of 25–36 mmHg [peak velocity less than 3 m/s] is minimal; a peak gradient of 36–64 mmHg [peak velocity 3–4 m/s] is moderate; a peak gradient greater than 64 mmHg [peak velocity greater than 4 m/s] is severe). The position of the pulmonary artery branches is unique following the Lecompte maneuver. The pulmonary artery branches are positioned anterior to the ascending aorta, best visualized from the high left parasternal view. The permissible maximum velocity across the pulmonary artery branches after an arterial switch operation is less than 2 m/s.

Systemic right ventricular (RV) systolic dysfunction is a common late complication in patients after an atrial switch operation. In most clinical cases, the assessment of global systolic function is qualitative. Quantitative methods include the measurement of fractional area change, tricuspid annular plane systolic excursion (TAPSE), and the peak systolic velocity of the RV myocardium at the tricuspid annulus level using tissue Doppler imaging (S′). In adults, a tricuspid annular plane systolic excursion (TAPSE) of less than 17 mm indicates RV systolic dysfunction. The peak systolic velocity of the tricuspid annulus (S′) reflects RV contractility and is evaluated using tissue Doppler imaging. Tricuspid annular S′ correlates with the RV fractional area change and TAPSE. S′ is preload- and heart rate-dependent. The lower limit of normal for S′ in adults is 9 cm/s; in children, the significance of a decrease should be calculated using z-scores. In adults, S′ <9 cm/s corresponds to an RV ejection fraction of <40%.

Atrial switch operation. Evaluation of blood flow in the pathways for the pulmonary and venae cavae. Flow obstruction is established when the maximum pressure gradient at the narrowest point of the baffle exceeds 10 mmHg (or maximum velocity exceeds 1.5 m/s).

Following the Rastelli procedure, subaortic obstruction, aortic regurgitation, and LV dysfunction are potential late complications. The severity of subaortic obstruction is determined by the systolic pressure gradient measured via continuous-wave Doppler: severe – greater than 50 mmHg; moderate – 30–50 mmHg; mild – less than 30 mmHg.

Residual ventricular septal defects are a common late complication, including intramural defects that may develop postoperatively.

Appendix B. Physician Action Algorithms

Appendix B1. Management algorithm for patients with TGA and intact ventricular septum (simple form)

Appendix B2. Management algorithm for patients with TGA and VSD

Appendix B3. Management algorithm for patients with TGA and concomitant pulmonary stenosis

Appendix B4. Algorithm for the use of diagnostic imaging methods in TGA

Appendix C. Patient Information

Dear parents, the diagnostic results revealed that your child has a complex congenital heart disease – transposition of the great arteries. By voluntarily consenting to the surgery, you must understand the purpose and risks of the procedure, which will be explained to you by the attending physician.

Transposition of the great arteries occurs in the early stages of embryonic development. The causes of embryogenesis disorders are numerous: maternal infectious diseases in early pregnancy, parental harmful habits, environmental and genetic factors, etc. Depending on the specific defect variant, hemodynamic disturbances and clinical manifestations can vary significantly. However, in all cases, they impair the physical condition and reduce the life expectancy of patients.

In certain cases, staged treatment for transposition of the great arteries may be required, with the first stage being a preparatory procedure. Radical correction of transposition of the great arteries is performed under cardiopulmonary bypass. It involves transferring the aorta to the left ventricle and the pulmonary artery to the right ventricle, as well as repairing associated cardiac anomalies. If anatomical correction is not feasible, a cavopulmonary shunt (or Fontan-type palliation) is employed, whereby blood from the venae cavae flows directly into the pulmonary artery, bypassing the heart.

In individual cases, complications may arise:

• heart failure;

• prolonged mechanical ventilation;

• acute kidney injury requiring peritoneal dialysis or hemodialysis;

• postoperative bleeding, large hematomas;

• infectious complications;

• hypersensitivity reactions (allergies) to medications, anesthetics, and contrast agents, which may manifest, for example, as itching.

Severe reactions, such as circulatory collapse, seizures, and respiratory compromise, are extremely rare and require inpatient treatment, potentially leading to irreversible consequences;

In most cases, surgery leads to an improvement in condition and the disappearance of symptoms. In some cases, repeat interventions may be required, most commonly associated with the child's growth.

Postoperative follow-up examinations are particularly important to timely evaluate the results of the repair and detect any potential complications.

Appendix G. Assessment Scales, Questionnaires, and Other Evaluation Tools

No.