Cor triatriatum: Clinical Guidelines

List of Abbreviations

ACG – angiocardiography

CHD — congenital heart disease

VSD — ventricular septal defect

ASD – atrial septal defect

CoA – coarctation of the aorta

PA – pulmonary artery

PV – pulmonary veins

LSVC – left superior vena cava

PH – pulmonary hypertension

LV — left ventricle

LA – left atrium

MV – mitral valve

MRI – magnetic resonance imaging

CI — circulatory insufficiency

RV – right ventricle

RA – right atrium

TAPVC – total anomalous pulmonary venous connection

PAPVR – partial anomalous pulmonary venous return

ECG — electrocardiography

EchoCG — echocardiography

Terms and Definitions

Angiocardiography – catheterization of the heart chambers and blood vessels, an invasive procedure performed for therapeutic or diagnostic purposes in cardiovascular pathology by introducing catheters into the heart cavity or the lumen of great vessels.

Pulmonary hypertension – a pathophysiological condition characterized by an increase in mean pulmonary artery pressure > 25 mm Hg, with the development of right ventricular heart failure as the most frequent cause of patient death.

Level of evidence (LoE) – the degree of certainty that the estimated effect of a medical intervention is true [1].

Grade of recommendation (GoR) – the degree of certainty that the effect of an intervention is reliable and that following the recommendations will bring more benefit than harm in a specific situation [1].

Echocardiography — an ultrasound imaging method aimed at examining the morphological and functional changes of the heart and its valvular apparatus.

1. Brief information on the disease or condition

1.1 Definition of the disease or condition

Classical (or typical) cor triatriatum sinister – a congenital heart defect in which the pulmonary veins (PV) drain into a 'proximal' chamber of the left atrium (LA), separated from the 'distal' chamber by a diaphragm (membrane) with one or more restrictive orifices [2].

In turn, the term 'cor triatriatum dexter' mentioned in the literature is used to designate various developmental anomalies of the heart with division of the right atrium and is not related to classical cor triatriatum

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

Due to the fact that cor triatriatum belongs to intrauterine developmental anomalies, any events affecting embryogenesis can lead to this defect. First of all, these include the effects of various physical, chemical, infectious, and toxic factors on the developing fetus. A hereditary nature of the pathology cannot be excluded either, as there are no data confirming or refuting this possibility. As a result of impaired embryonic development, the septum in the left atrium is formed due to the delamination of the inner layer of the atrial wall during improper positioning of the pulmonary veins. An alternative variant of forming a separate chamber instead of a septum is also possible [3]. That is, this anomaly is an intermediate variant between normal anatomy and anomalous pulmonary venous drainage, based on the positioning and separation of the pulmonary vessels. As a result of this anomaly, the left atrial chamber is divided by a membrane.

In typical cases of cor triatriatum, a fibrous or fibromuscular membrane with one or more orifices is present, dividing the left atrial cavity. Usually, the membrane is thick, the orifice in it is tubular [4,5], and it may contain calcifications. The membrane divides the LA into an upper or upper-posterior chamber (the common pulmonary-venous chamber, proximal) and a lower or anterior-inferior chamber (distal). The PVs empty into the former, while the latter communicates with the LA appendage and mitral valve. The membrane extends from the interatrial septum in the fossa ovalis region to the anterolateral wall of the LA, attaching just below the entry of the lower PV orifices. Most frequently, the membrane attaches above the oval foramen [6] or from the middle part of the oval fossa, with the latter being divided into two parts. Usually, the wall of the proximal chamber is thick, whereas the wall of the distal chamber is thin.

In 90% of cases, the proximal chamber communicates with the distal left atrial chamber through a central or eccentric orifice in the membrane. In 10% of cases, communication between the accessory chamber and the LA proper is entirely absent. In such cases, there is communication with the RA directly via an ASD or indirectly via anomalous pulmonary venous connection. Despite the high pressure in the proximal chamber, the PVs are not dilated. Relative to the superior vena cava and RA, the right PVs draining into the proximal chamber are located as in a normal heart. The RV is usually enlarged, but this enlargement depends on the presence and degree of left-to-right shunt at the atrial level. The LV is of normal size or moderately hypoplastic. The fossa ovalis may be located between the common pulmonary-venous chamber and the RA, but more frequently in the septum between the LA and RA. If a patent foramen ovale is present, it is stretched.

In cor triatriatum, the right and left PVs may form a separate 'chamber' behind, slightly above, or medial to the LA, similar to the common venous sinus characteristic of TAPVC.

Among associated intracardiac anomalies, the combination of cor triatriatum with anomalous drainage of PVs is most frequently observed [2,7-12].

Among other associated developmental heart anomalies, the following can be noted [13-17]: ASD, LSVC, VSD, CoA, CAVC, TOF.

In the isolated form of the defect, hemodynamic disturbances reduce to obstructed blood outflow from the lungs and are similar to those observed in mitral stenosis. The degree of their severity is inversely proportional to the area of communication between the heart chambers.

In the absence of communication between the chamber into which the PVs drain and the left atrioventricular orifice, postnatal circulation is possible only in the presence of an interatrial defect through which (or which) the RA communicates with both LA chambers. In these cases, blood from the upper chamber first enters the RA and then, through the part of the defect located below the membrane, returns to the LA and from there to the LV [2,18].

Naturally, the entry of mixed blood into the systemic circulation causes hypoxemia, while the degree of pulmonary venous congestion, pulmonary hypertension, and LV cardiac output volume depends on the size of the interatrial communication.

The localization of the interatrial defect determines the likelihood of two types of hemodynamic disturbance in the second anatomical form of the membrane. If the right atrium communicates only with the upper chamber through the defect, the hemodynamic disturbance is identical to Lutembacher syndrome (a combination of congenital ASD with acquired mitral stenosis). If the defect is located below the membrane, so-called shunt hypoxemia is added to the hemodynamic disturbances characteristic of mitral stenosis [18-20,35].

1.3 Epidemiology of the Disease or Condition

Cor triatriatum is a fairly rare congenital anomaly, observed in approximately 0.1-0.4% of cases among all congenital heart defects [2,7,18,21].

The natural history and prognosis depend on the size of the communication between the proximal chamber and the distal LA. In approximately 35% of cases, the interatrial communication is less than 3 mm in diameter—an extreme form of stenosis, almost equivalent to atresia. In 35% of cases, the orifice size ranges from 3 to 6 mm, corresponding to severe stenosis.

Patients in both groups die in early childhood from heart failure. In the first group, death may occur within the first 6 months of life, and in the second group, before the age of 2 years [22-24]. With a large orifice diameter (greater than 7 mm in infants and adolescents), the defect presents with the clinical picture of mitral stenosis, and life expectancy increases to several years. Thus, in the majority of patients, the orifice is restrictive, and about 70% of patients with classical cor triatriatum die in early childhood [2]. The prognosis of the disease is more favorable when there is communication with the right atrium, as decompression of the common pulmonary-venous chamber occurs. The course of the disease with a large left-to-right shunt is more favorable in contrast to patients with a restrictive orifice in the membrane [2,18,25].

Very rarely, cor triatriatum may be detected in adults [26-28]. Such late diagnosis is due to lesser membrane obstruction.

1.4 Features of Coding the Disease or Condition

Q24.2 — Cor triatriatum.

1.5 Classification of the disease or condition

Classification I [29]:

I. The accessory chamber receives all PVs and connects to the LA:

A – without other communications (classical form of the defect);

B – with additional anomalous communications (direct connection to the RA or connection via TAPVC).

II. The accessory chamber receives all PVs and does not connect to the LA:

A – connects directly to the RA;

B – connects to the RA via TAPVC.

III. Incomplete form of cor triatriatum (part of the PVs drains directly into the LA, part into the accessory chamber):

A – the accessory chamber connects to the LA;

B – the accessory chamber connects to the RA.

Classification II [30]:

A. The accessory common pulmonary venous chamber receives all pulmonary veins and communicates with the LA.

1. no other connections (classical cor triatriatum);

2. other anomalous connections:

a) directly with the RA;

b) with total anomalous pulmonary venous connection.

B. The accessory common pulmonary venous chamber receives all pulmonary veins and does not communicate with the LA.

1. anomalous connection directly with the RA (cardiac type TAPVC, in which all pulmonary veins initially drain into a venous collector).

2. with total anomalous pulmonary venous connection (supra- or infracardiac type TAPVC).

C. Subtotal cor triatriatum.

1. The accessory common pulmonary venous chamber receives part of the pulmonary veins and connects to the LA:

a) the remaining pulmonary veins connect to the left atrium;

b) the remaining pulmonary veins connect anomalously (partial cor triatriatum with PAPVC).

2. The accessory common pulmonary venous chamber receives part of the pulmonary veins and connects to the RA:

a) the remaining pulmonary veins connect to the LA;

b) the remaining pulmonary veins connect anomalously (mixed type TAPVC).

1.6 Clinical presentation of the disease or condition

Clinical manifestations of the disease are extremely diverse and depend on the severity of the membrane defect stenosis, as well as the direction and volume of the blood shunt through the atrial septal defect [2,23,25,31,35].

With severe stenosis from the first days of life, cyanosis, dyspnea, cough, and congestive rales in the lungs occur and progressively worsen. Cyanosis of visible mucous membranes and skin is caused by the communication between the left and right atria via the foramen ovale or atrial septal defect. Subsequently, heart failure and delayed physical development are observed. Under more favorable conditions, when the orifice in the membrane exceeds 6–7 mm [2,18,25,32,33], symptom progression is slower.

Patients are frequently treated for pneumonia, and only echocardiography helps detect the defect. Other symptoms are related to right ventricular failure, such as hepatomegaly, facial and lower extremity edema. Feeding difficulties and poor weight gain are noted. The majority of patients die from right ventricular failure [2,8,25,34,35].

Unlike patients with mitral stenosis, patients with cor triatriatum have no history of a previous rheumatic process [2,26-28].

2. Diagnostics, medical indications and contraindications for diagnostic methods

The diagnosis of cor triatriatum is verified based on the cumulative data of the disease development history, complaints of the patients' parents, clinical manifestations of the defect, and instrumental diagnostic methods.

2.1 Complaints and Anamnesis

(Reliability of Evidence Level C, Confidence Level in Recommendations 5).

Comments: Depending on the degree of hemodynamic impairment, there is significant variability in the clinical course of cor triatriatum. The patient's condition depends on the size of the membrane orifices, the degree of impaired pulmonary venous drainage, and the anatomical variant of congenital heart disease (association with various variants of anomalous pulmonary venous drainage, presence of an atrial septal defect, and left ventricular dimensions). When taking the medical history, it is necessary to clarify whether the patients have dyspnea, palpitations, decreased exercise tolerance, poor weight gain, and frequent bronchopulmonary infectious diseases.

2.2 Physical Examination

(Reliability of Evidence Level C, Confidence Level in Recommendations 5).

Comments: Patients with developing pulmonary hypertension generally present with malnutrition and an asthenic body type. When signs of right ventricular failure join the clinical picture, patients may exhibit edema in the lower extremities, lower back, and anterior abdominal wall. Pronounced impairment of pulmonary venous drainage can lead to the development of lip cyanosis and facial flushing—the so-called "mitral butterfly" appearance.

With the development of RV hypertrophy (isolated or combined with myogenic dilation) due to the heart defect, an enhanced apex beat and widespread pulsation in the epigastric region may occur [34].

(Reliability of Evidence Level C, Confidence Level in Recommendations 5).

Comments: The auscultatory findings of the defect are non-specific and in some cases may be completely absent. In most cases, the first heart sound is normal or slightly accentuated; the second heart sound, heard along the left sternal border, is loud and sometimes split. In cases of pronounced impairment of pulmonary venous drainage and the development of pulmonary hypertension, an accentuation of the second heart sound over the pulmonary artery is noted. With the development of right heart dilation, a systolic murmur of tricuspid regurgitation may occur. With long-standing defects and the development of relative pulmonary valve regurgitation due to elevated pressure, a Graham Steell functional diastolic murmur may be auscultated in the second intercostal space to the left of the sternum and along the left sternal border [35].

2.3 Laboratory Diagnostics

In patients with a non-restrictive orifice in the membrane, LA findings are non-specific.

2.4 Instrumental Diagnostics

(Level of Evidence: C, Strength of Recommendation: 5).

Comments: There are no specific signs on ECG. In most cases, right axis deviation is observed. The following may also be registered:

• increased P wave amplitude in leads II and V;

• signs of severe RV hypertrophy with a qR pattern in lead V1;

• deep negative T waves in the right precordial leads, less commonly in leads II, III, and aVF, indicating RV subendocardial myocardial ischemia associated with high pressure within the ventricle.

Signs of left atrial hypertrophy may appear, though not consistently [18,25,35].

• All patients are recommended to undergo targeted chest radiography to determine cardiac configuration and the status of the pulmonary circulation [7,8,10,18,25,35].

(Reliability of Evidence Level C, Confidence Level in Recommendations 5).

Comments: On the posteroanterior chest radiograph, the cardiac silhouette is mildly to moderately enlarged, appearing almost normal in adults. Oblique projections reveal cardiac enlargement at the expense of the right heart chambers. The pulmonary vascular pattern is enhanced along the venous bed, pulmonary edema may occasionally be visualized, and the pulmonary artery trunk is dilated [2,8,25,35].

(Level of Evidence: C, Strength of Recommendation 5).

Comments: Left cor triatriatum. In the parasternal long-axis view of the left ventricle, a fixed linear echodensity is visualized, extending from the free wall of the left atrium to the atrial septum. The location and degree of attachment to the atrial septum are variable. In the apical 4-chamber view, the presence of the linear echostructure should be confirmed and artifacts excluded.

Differential echocardiographic diagnosis of cor triatriatum includes partial anomalous pulmonary venous return to the coronary sinus, supravalvular mitral ring (between the left atrial appendage and the base of the anterior mitral leaflet), and a visible fold of the LA wall at the junction of the lower left pulmonary vein.

When cor triatriatum is detected, the size, number, and location of the membrane orifices should be determined. Three-dimensional echocardiography with color Doppler mapping can facilitate the identification of the orifice [36]. It is also critical to determine the drainage of all four pulmonary veins. In complex cases, transesophageal echocardiography allows easy visualization of the intra-atrial membrane and determination of the transmembranous gradient to assess the severity of pulmonary outflow obstruction. A low-velocity phase flow with a peak velocity of less than 1 m/s indicates the absence of obstruction. Concomitant mitral stenosis can mask moderate obstruction at the level of the atrial membrane. Therefore, it is important to examine the morphology of the mitral valve and subvalvular apparatus.

Doppler echocardiography is useful in detecting moderate or severe pulmonary venous outflow obstruction. In cases of mild obstruction, a provocative test, such as exercise prior to the echocardiographic examination, is recommended.

Cor triatriatum dextrum. A membrane divides the right atrium into proximal (superior) and distal (inferior) chambers. The superior chamber connects with the superior (and inferior) vena cava, while the inferior chamber communicates with the tricuspid valve, the right atrial appendage, and the inferior vena cava [37]. Venous outflow restriction (orifice diameter in the membrane, velocity/pressure gradient between the atrial chambers) and the direction of blood shunting in the presence of a patent foramen ovale (PFO) / atrial septal defect (ASD) should be assessed. Echocardiographically, cor triatriatum dextrum should be differentiated from Ebstein's anomaly [38].

(CRA C, LOR 4).

Comments: CT plays an increasingly important role in the diagnosis of cor triatriatum: it provides excellent spatial resolution and rapid data acquisition, allows visualization of epicardial coronary arteries and arterial collaterals, and detects parenchymal lung disease. Ventricular dimensions and function can be assessed in less time compared to MRI. CT is currently more widely available than MRI and therefore plays a special role in emergency situations. Cardiac CT is an alternative to MRI in patients with implanted pacemakers or defibrillators [2,64-66].

(LoE C, GoR 4).

Comments: Cardiac MRI improves visualization capabilities, particularly for assessing ventricular volume overload and quantifying shunts. The technique provides three-dimensional anatomical reconstructions with high spatial and temporal resolution, volumetric measurements, vascular assessment, and myocardial fibrosis evaluation. MRI is used in adult patients with cor triatriatum in the following clinical situations:

- as an alternative to echocardiography when both methods can provide similar information;

- as an adjunctive method when echocardiographic data are ambiguous or borderline, such as left ventricular volumes and ejection fraction, which may be critical in managing adult patients with cor triatriatum (e.g., assessing volume overload and valvular regurgitation);

- MRI is more informative than echocardiography in quantifying right ventricular volumes and ejection fraction, right ventricular outflow tract obstruction, pulmonary regurgitation, evaluating the pulmonary arteries (stenosis, aneurysms) and aorta (aneurysm, dissection, coarctation); systemic and pulmonary veins (anomalous drainage, obstructions, etc.), collaterals and arteriovenous malformations (superior to CT), in coronary artery disease (CAD) (inferior to CT), assessing intra- and extracardiac masses (inferior to CT), quantifying myocardial mass (left and right ventricles), detecting and quantifying myocardial fibrosis/scar (late gadolinium enhancement); and tissue characterization (fibrosis, fat, etc.) [39,67].

(LoE C, GoR 4).

Comments: A reliable sign of the defect is the presence of two regions with different pressures in the left atrium. Passing a catheter into both chambers via an atrial septal defect is extremely rare. An indicator suggesting the anomaly is the detection of an elevated pulmonary capillary wedge pressure (PCWP), as well as a gradient between the PCWP and the left ventricular end-diastolic pressure [13]. Intraadrial shunting may be detected. The direction of the shunt varies and depends on the location of the defect relative to the left atrial septum. If there is communication between the upper chamber of the left atrium and the right atrium via an oval foramen or ASD, a left-to-right shunt is observed, which can occasionally be substantial [40].

Selective pulmonary angiography in some cases reveals slowed blood flow through the pulmonary veins, and in cases of dense opacification of the left atrium, it can sometimes establish its two-chamber structure. With very large atrial communications, the angiocardiographic picture differs little from total anomalous pulmonary venous return [15,40].

2.5 Other Procedures

(Reliability of Evidence Level C, Confidence Level in Recommendations 5).

• Before hospital discharge, all patients are recommended to undergo echocardiography for postoperative monitoring following the surgical procedure [2,25,35].

(Level of Evidence: C, Strength of Recommendation: 5).

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

3.1 Conservative Treatment

Supportive therapy

The treatment strategy for cor triatriatum is determined by the size of the membrane orifice, the degree of pulmonary venous outflow obstruction, and the size of the ASD shunt (if present). Primary conservative treatment aims to reduce pulmonary venous congestion and is used to stabilize the patient's condition while preparing for surgery.

(Reliability of Evidence Level C, Confidence Level in Recommendations 5).

Comments: In patients with heart failure, it is advisable to use conservative therapy with diuretics. Treatment should not be prolonged and is used until surgical correction of the congenital heart defect.

Heart failure is the most frequent problem in adult patients with cor triatriatum or following surgical correction of the defect. Therapy in such cases is carried out using established heart failure guidelines [41,42].

(LoE B, GoR 3).

Comments: Diuretics are used in children for the treatment of heart failure, reducing myocardial preload and afterload as well as extracellular fluid volume, thereby improving the functional status of internal organs. Doses are selected individually, starting with the minimum and gradually increasing to a clinically effective level. For mild fluid retention, thiazides are used:#Hydrochlorothiazide** (C03AA03) is used off-label in children under 3 years of age (solid dosage form). #Hydrochlorothiazide** (C03AA03), according to the instructions, is used at a dose of 1–2 mg/kg/day or 30–60 mg/m² of body surface area once daily, although higher doses are described in the literature: in children under 6 months – 2–3.3 mg/kg/day in 2 divided doses, over 6 months – 2 mg/kg/day in 2 divided doses[73]. The potassium-sparing diuretic #Spironolactone** (potassium-sparing diuretics / aldosterone antagonists / C03DA01) can be used alongside thiazides in children off-label at a dose of 1–3 mg/kg/day [73-75]: in premature infants under 32 weeks of gestation – 1 mg/kg/day, newborns – 1–2 mg/kg/day, in infants and children – 1–3 mg/kg/day. #Spironolactone** is frequently used in combination with loop diuretics (furosemide**) as a potassium-sparing diuretic. In children with impaired renal function or pronounced fluid retention, the use of loop diuretics is recommended: #furosemide** (C03CA01) is prescribed to newborns at a dose of 1 mg/kg/dose every 12–24 hours per orally or intravenously as a bolus; to infants and children – 1–4 mg/kg/day in 2–4 divided doses orally, and 1–2 mg/kg/dose every 6–12 hours intravenously[73]; at a continuous infusion rate of 0.1–0.4 mg/kg/h[74,75]. According to the drug prescribing information, furosemide** (C03CA01) is administered intravenously at a dose of 1 mg/kg/day, not exceeding 20 mg/day; tablets are prescribed from 3 years of age at 2 mg/kg/day, not exceeding 40 mg. With intravenous administration, the effect appears in 10–15 minutes and lasts up to 3 hours. In concomitant renal failure, the dose of #furosemide** is increased to 5 mg/kg/day or more [87]. There are indications of the safety and efficacy of using the loop diuretic #torasemide off-label in children [77-86]. #Torasemide may be more effective than #furosemide** in treating heart failure in children due to higher diuretic activity consistent with potassium-sparing and anti-aldosterone effects. In children, #torasemide is used at a dose of 0.42–0.48 mg/kg/day (ranging from 0.18 to 0.8 mg/kg/day) in a single daily dose[76]When transferring a child from #furosemide** to #torasemide, the dose is adjusted as follows: 1 mg of #furosemide** corresponds to 0.2 mg of #torasemide.[76].

(Level of Reliable Evidence C, Uncertainty of Evidence Level 5).

Comments: To increase cardiac output, adrenergic and dopaminergic agents (inotropic drugs) are used (dobutamine**, dopamine**) [52,53]. These drugs are used in children of all age groups (from birth to 18 years) in the setting of low cardiac output, but with caution.

(Reliability of Evidence Level C, Confidence Level in Recommendations 5).

Comments: There is no compelling evidence supporting the efficacy and safety of ACE inhibitors, angiotensin II receptor blockers, calcium channel blockers, or beta-blockers in patients with cor triatriatum and pulmonary hypertension.

(Reliability of Evidence Level C, Confidence Level in Recommendations 5).

3.2 Surgical Treatment

• Surgical treatment is recommended for patients with cor triatriatum with a restrictive opening between the proximal and distal chambers [2,25,32,35].

(CRA C, LOR 4).

• Surgical correction of congenital heart disease is recommended for patients with cor triatriatum associated with concurrent congenital heart anomalies [71,72].

(CRA C, LOR 4).

• Surgical correction of cor triatriatum is recommended for adult patients with clinical manifestations [72].

(CRA C, LOR 4).

• Surgical correction of the defect is recommended for atypical forms of cor triatriatum accompanied by a severe clinical course: the common pulmonary-venous chamber opens into the right atrium; there is no communication or a restrictive communication exists between the common pulmonary-venous chamber and the left atrium with a small foramen ovale between the right atrium and the left atrium, with a large left-to-right shunt combined with decreased inflow to the left atrium and left ventricle [2,25,32,35].

(Reliability of Evidence Level C, Confidence Level in Recommendations 5).

• Surgical correction of cor triatriatum is recommended in patients with a non-restrictive opening in the membrane in whom the defect limits work capacity or contributes to the development of secondary diseases [2,25,32,35].

(Reliability of Evidence Level C, Confidence Level in Recommendations 5).

3.3 Endovascular interventions

• In patients with cor triatriatum in a critical condition with a restrictive communication between the chambers, it is recommended to use balloon vasodilation using a double-balloon technique as an emergency intervention [2,25,35].

(Reliability of Evidence Level C, Confidence Level in Recommendations 5).

Comments: the use of this technique leads to the regression of symptoms and allows the patient to be stabilized from a critical condition, serving as a life-saving procedure.

3.4 Other treatment

No

4. Medical Rehabilitation and Sanatorium-Resort Treatment

• Within 6 months after surgical correction of cor triatriatum under cardiopulmonary bypass in a patient with a complicated postoperative course (residual pulmonary hypertension, heart failure, infectious complications, repeated surgical interventions during the same hospitalization), it is recommended to undergo rehabilitation in a specialized cardiological medical institution [88].

(LoE C, GoR 5).

Comments: The following conditions may occur after correction of cor triatriatum:

- Restenosis of the resected membrane [4,22].

- Persistence of pulmonary hypertension may also be observed after successful correction of congenital heart disease. Persistent pulmonary hypertension after correction of cor triatriatum belongs to group 1 [55]. If clinical manifestations are present, its treatment is carried out in accordance with available guidelines [46].

- Rhythm and conduction disorders (ventricular and supraventricular arrhythmias, bundle branch block, atrioventricular blocks, and sudden cardiac death) may occur both immediately after surgical correction and at later follow-up periods.

(LoE C, GoR 5).

Comments: Eight months after the repair of cor triatriatum, patients may be cleared for participation in all competitive sports in the absence of: 1) signs of pulmonary arterial hypertension; 2) symptomatic tachyarrhythmias or second- or third-degree AV block; 3) signs of myocardial dysfunction; 4) ventricular or atrial tachycardia.

5. Prevention and Dispensary Observation

The prognosis after surgical correction of cor triatriatum is favorable, provided that the congenital heart disease is corrected in a timely manner. Life expectancy and physical performance may be limited in the presence of pulmonary hypertension.

(CRA C, LOR 4).

Comments: The frequency of follow-up visits with a pediatric cardiologist/cardiologist is at one month, 3, 6, and 12 months after surgery. The follow-up protocol includes ECG and echocardiography, as well as exercise stress testing and pulse oximetry when necessary. Subsequent patient monitoring is carried out at intervals of 3–36 months [58,59].

Following surgery, it is recommended to remain under medical follow-up for one year, and thereafter according to clinical indications. Patients with left ventricular dysfunction, residual shunt, or residual pulmonary hypertension should be monitored annually in specialized centers. In patients with a good clinical and hemodynamic result of the surgery, preserved left ventricular function, absence of pulmonary hypertension, and no other lesions, follow-up visits may be considered at intervals of 3–5 years.

When determining the frequency of follow-up, one should be guided by the presence of heart failure symptoms, hemodynamic status, cardiac arrhythmias, hypoxemia, etc. Depending on these factors, all patients with CHD 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 dilation of the aorta or ventricle(s);

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

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

- absence of hypoxemia;

- cardiac arrhythmias not requiring treatment;

- absence of signs of pulmonary hypertension;

- normal kidney and liver function.

Group C

- heart failure functional class III;

- moderate or significant stenosis and/or valve regurgitation (degrees II–III), arterial or venous stenosis, moderate dilation of the aorta or ventricle(s);

- LVEF 40–49%, RV EF 35–39%;

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

- moderately severe hypoxemia (SatpO2 ≥ 85%);

- cardiac arrhythmias controlled by therapy;

- pulmonary hypertension (pulmonary hypertension FC I–II);

- internal organ dysfunction controlled by therapy.

Group D

- heart failure FC IV;

- significant aortic dilation;

- severe hypoxemia (SatpO2 < 85%);

- cardiac arrhythmias refractory to therapy;

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

- internal organ dysfunction refractory to ongoing therapy.

Depending on whether a patient with corrected or uncorrected ventricular septal defect belongs to a particular group, varying frequencies of monitoring and scopes of required examinations are recommended:

(Level of Reliable Evidence C, Uncertainty of Evidence Level 5).

(Level of Reliable Evidence C, Uncertainty of Evidence Level 5).

Comments: Echocardiography makes it possible to determine the presence of tricuspid regurgitation, restenosis at the level of the resected membrane, ventricular dysfunction, and elevated pulmonary artery pressure.

(Level of Reliable Evidence A, Uncertainty of Evidence Level 2).

(Level of Reliable Evidence C, Uncertainty of Evidence Level 5).

(Level of Reliable Evidence C, Uncertainty of Evidence Level 5).

Comments: For any type of congenital heart disease in the correction of which animal-derived*** (192060) or synthetic*** (192080) cardiovascular patches were used, if indicated, bacterial endocarditis prophylaxis is carried out for 6 months after surgery or lifelong if residual shunts or valvular regurgitation persist. Endocarditis prophylaxis is performed during dental procedures accompanied by damage to the oral mucosa (tooth extraction, manipulations in the periapical zone of the tooth, etc.). Prophylaxis of infective endocarditis consists of oral administration, 30–60 minutes before the procedure, of amoxicillin** at a dose of 50 mg/kg (children) or 2 g (adults) (in case of allergy to benzylpenicillin** or ampicillin**, #clindamycin** is used (off-label in children 12 years of age) at a dose of 20 mg/kg (children) or 600 mg (adults)). [62]

6. Organization of Medical Care

Indications for hospital admission to a medical organization:

1) presence of symptoms of heart failure;

2) presence of pulmonary hypertension;

3) elective surgical treatment.

Indications for emergency hospitalization:

1) deterioration of the patient's functional status due to the progression of circulatory insufficiency symptoms or cardiac arrhythmias;

2) infective endocarditis;

3) acute cardiac arrhythmias.

Indications for discharging a patient from a medical organization:

1) absence of obstruction to blood flow at the atrial level;

2) absence/compensation of symptoms of circulatory insufficiency.

7. Additional Information

(Level of Reliable Evidence C, Uncertainty of Evidence Level 5).

(Reliability of Evidence Level C, Confidence Level in Recommendations 5).

Criteria for Evaluating the Quality of Medical Care

References

Appendix A1. Working Group Composition

1. Avramenko A.A. (Samara)

2. Arnautova I.V., MD, "Association of Cardiovascular Surgeons of Russia", (Moscow)

3. Bogdanov V.N. (Chelyabinsk)

4. Bokeria L.A., Academician of the RAS, "Association of Cardiovascular Surgeons of Russia", (Moscow)

5. Boriskov M.V., DSc in Medical Sciences, (Krasnodar)

6. Borisova N.A., "Russian Scientific Society of Endovascular Diagnostics and Treatment Specialists", (Saint Petersburg)

7. Gorbatikov K.V., DSc in Medical Sciences, (Tyumen)

8. Gorbatykh Yu.N., DSc in Medical Sciences, (Novosibirsk)

9. Kim A.I., DSc in Medical Sciences, "Association of Cardiovascular Surgeons of Russia", (Moscow)

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

11. Krivoshchekov E.V., DSc in Medical Sciences, (Tomsk)

12. Kupryashov A.A., DSc in Medical Sciences, (Moscow)

13. Levchenko E.G., (Moscow)

14. Movsesyan R.R., DSc in Medical Sciences, "Association of Cardiovascular Surgeons of Russia", (Saint Petersburg)

15. Plotnikov M.V., Candidate of Medical Sciences, (Astrakhan)

16. Pursanov M.G., Doctor of Medical Sciences, (Moscow)

17. Sinelnikov Yu.S., Doctor of Medical Sciences, (Perm)

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

19. Chernogrivov A.E., MD, Association of Cardiovascular Surgeons of Russia, (Moscow)

20. Shatalov K.V., MD, "Association of Cardiovascular Surgeons of Russia" (Moscow)

There is no conflict of interest.

All members of the Working Group have confirmed that they have no financial support or conflicts of interest to disclose.

Appendix A2. Methodology for Developing Clinical Guidelines

Target audience for these clinical guidelines:

1. Pediatric Cardiologist

2. Cardiologist

3. Cardiovascular Surgeon

4. Ultrasound Diagnostics Physician

5. Pediatrician

6. X-ray Endovascular Diagnostics and Treatment Physician

During the development of the CPG, a new system of levels of evidence (LE) and grades of recommendation (GR) scales for therapeutic, rehabilitation, preventive, and diagnostic interventions (Tables 1, 2, and 3) introduced in 2018 by the Center for Expertise and Quality of Medical Care of the Russian Ministry of Health was used.

Table 1. Scale for assessing levels of evidence (LE) for diagnostic methods (diagnostic interventions).

Table 2. Scale for assessing levels of evidence (LE) for prevention, treatment, and rehabilitation methods (preventive, therapeutic, rehabilitation interventions).

Table 3. Scale for grading the levels of evidence (LE) for prevention, diagnostic, treatment, and rehabilitation methods (preventive, diagnostic, therapeutic, and rehabilitative interventions).

Procedure for updating clinical guidelines.

The mechanism for updating clinical guidelines provides for their systematic revision at least once every three years, as well as upon the emergence of new evidence-based medicine 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 the Basics of Protecting the Health of Citizens in the Russian Federation (Federal Law No. 323-FZ of November 21, 2011)

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

Appendix B. Physician Action Algorithms

Appendix C. Patient Information

Cor triatriatum (cor triatriatum sinister) is a congenital heart defect in which the pulmonary veins drain into the "proximal" chamber of the left atrium, separated from the "distal" chamber by a membrane with one or more openings.

Cor triatriatum is a rather rare congenital anomaly and is observed in approximately 0.1-0.4% of cases among all congenital heart defects.

Among associated intracardiac anomalies, the most frequent combination of cor triatriatum is with anomalous pulmonary venous drainage.

Among other associated cardiac developmental anomalies, atrial septal defect, left superior vena cava, ventricular septal defect, coarctation of the aorta, complete atrioventricular canal, and Tetralogy of Fallot can be noted.

In the isolated form of the defect, hemodynamic disturbances result in impeded blood outflow from the lungs and are similar to those observed in mitral stenosis. The severity of these disturbances is inversely proportional to the area of communication between the heart chambers.

Clinical manifestations of the disease are extremely diverse and depend on the degree of membrane defect stenosis, as well as the direction and volume of blood shunting through the atrial septal defect.

With severe stenosis from the first days of life, cyanosis, dyspnea, cough, and congestive rales in the lungs appear and progressively increase. Cyanosis of the visible mucous membranes and skin is caused by the communication between the left and right atria through the foramen ovale or an atrial septal defect. Subsequently, heart failure and physical developmental delay are noted. Under more favorable conditions (larger size of the opening in the membrane), symptom progression occurs more slowly.

Patients are frequently treated for pneumonia, and only an echocardiographic examination helps identify the defect. Other symptoms relate to right ventricular failure – hepatomegaly, facial and lower extremity edema. Feeding difficulties and poor weight gain are noted. Most patients die from right ventricular failure.

The natural course and prognosis depend on the size of the communication between the proximal chamber and the distal left atrium. In approximately 35% of cases, the intra-atrial communication is less than 3 mm in diameter; an extreme form of stenosis, almost equivalent to atresia. In 35% of cases, the opening size ranges from 3 to 6 mm and corresponds to severe stenosis.

Patients in both groups die in early childhood from heart failure. In the first group, death may occur during the first 6 months of life, and in the second group, before 2 years of age. With a large diameter of the opening (more than 7 mm in young children and adolescents), the defect presents with clinical features of mitral stenosis, and life expectancy increases to several years. Thus, in the majority of patients, the opening is restrictive, and about 70% of patients with classic cor triatriatum die in early childhood. The prognosis of the disease is more favorable if there is an existing communication with the right atrium, as decompression of the common pulmonary-venous chamber occurs. The course of the disease with a large left-to-right shunt is more favorable compared to patients with a restrictive opening in the membrane.

Given the varying prognosis in different patients with cor triatriatum, the presence of a left atrial membrane cannot be considered an absolute indication for surgery. Absolute indications for surgical treatment include: patients with a small (restrictive) orifice in the membrane between the chambers, adult patients with clinical manifestations, and patients with cor triatriatum combined with associated congenital heart anomalies. Relative indications are present in patients with a non-restrictive orifice in the membrane in whom the defect limits working capacity or contributes to the development of secondary diseases.

The radical method of treatment for cor triatriatum is resection of the membrane that creates an obstruction to blood flow within the left atrium. In cases of extremely severe condition, surgery becomes an emergency intervention as the only possible life-saving measure for the patient. In this capacity, it is most frequently performed in infants and young children.

The operation for radical correction of the defect is extremely effective; however, it is difficult to objectively characterize mortality because the defect is very rare, and the experience of individual authors is limited to isolated observations.

According to various authors, hospital mortality ranges from 0 to 50%, with an average of 15%. 20-year survival after defect correction is 83–100% and depends on associated congenital heart defects and the presence of severe pulmonary hypertension.

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

No.