Prolonged QT interval syndrome

Instrumental screening of arrhythmias

To identify patients with suspected or proven ventricular tachyarrhythmias, two main imaging and electrical activity assessment methods are used.

1. Standard 12-lead ECG This is the baseline diagnostic method that allows the detection of:

• Hereditary channelopathies: long and short QT syndromes, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia.
• Cardiomyopathies: hypertrophic cardiomyopathy (HCM) and arrhythmogenic right ventricular cardiomyopathy (ARVC).
• Structural pathology: AV blocks, bundle branch blocks, ventricular hypertrophy, and pathological Q wave (indicating infiltrative pathology or coronary artery disease).

It is important to remember that the administration of certain drugs and electrolyte imbalances can significantly distort the electrocardiographic picture, causing QRS complex prolongation or repolarization abnormalities.

2. Echocardiography (EchoCG) This method surpasses MRI and CT in availability and cost-effectiveness. EchoCG has high accuracy in diagnosing congenital defects, valvular and myocardial diseases associated with ventricular arrhythmias. Additionally, regional wall motion and left ventricular systolic function are evaluated.

Drug toxicity and monitoring

Many pharmacological agents require strict monitoring due to toxic effects, including a direct impact on cardiac conduction.

• Azithromycin: can provoke long QT syndrome, and also exhibits ototoxicity and causes gastrointestinal disorders. Requires mandatory ECG monitoring, audiogram, and patient interview.
• Arsenic trioxide: requires an ECG (QT evaluation) at least once a week during the remission induction phase, and then every 2–3 weeks.
• Other antibiotics: Amikacin threatens nephro- and ototoxicity (tinnitus); Clarithromycin and Imipenem/cilastatin — the development of hepatitis; Cefoxitin and Co-trimoxazole are hazardous due to hematotoxicity (leukopenia, anemia). Important: cefoxitin can interfere with serum creatinine tube assays, requiring alternative measurement methods, and ethambutol damages the optic nerve, requiring color vision tests.

Pediatric follow-up and prevention

Dispanserization (active clinical follow-up) of children with arrhythmias has no strict time limits. Patients are managed by pediatricians and cardiologists until transition to adult care.

Post-discharge examination schedule:

1. First 3 months — monthly.
2. From 3 to 12 months — once a quarter.
3. Older than 1 year — every six months.

The basis of follow-up control is a standard ECG, supplemented by 24-hour Holter monitoring when necessary.

Preventive strategy includes eliminating triggers and maintaining normal electrical activity:

• Early screening is performed during periods critical for arrhythmia manifestation: in newborns, at ages 4–5, 7–8, and during puberty (12–13 years).
• Secondary prevention is based on physical therapy, psychological counseling, and courses of metabolic support (antioxidants, membrane stabilizers) and nootropics.

Prognosis and autonomic nervous system influence

In most cases, pediatric arrhythmias are benign and do not shorten life expectancy. However, in newborns and infants, the risk of progression to heart failure or arrhythmogenic cardiomyopathy is significantly higher, which threatens disability or death.

Poor prognostic criteria:

• Acquired complete AV block.
• Atrial fibrillation.
• Chronic and paroxysmal tachycardias.

Predictors of sudden cardiac death (SCD): long QT syndrome, severe forms of sick sinus syndrome (SSS), as well as ventricular tachyarrhythmias presenting with syncope, arterial hypertension, or acute heart failure.

An important background for the development of pathologies is vegetative dystonia syndrome (VDS). While not an independent nosology, VDS triggers a cascade of psychosomatic reactions (including coronary artery disease and hypertension) in combination with other factors. Somatic diseases exacerbate ANS dysfunction, creating a vicious cycle.

Class and exam questions

What else to study on this topic

• Catecholaminergic polymorphic ventricular tachycardia
• Arrhythmogenic right ventricular cardiomyopathy (ARVC)
• Toxic effects of specific antibacterial therapy
• 24-hour Holter ECG monitoring for arrhythmias
• Pathogenetic role of vegetative dystonia syndrome

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.