Ventricular tachycardia in children: symptoms, diagnosis, treatment

Ventricular tachycardia occupies a special place in arrhythmology, as it has a wide variability of clinical manifestations and in some cases - a high probability of an unfavorable prognosis. Many ventricular tachycardias are associated with a high risk of developing ventricular fibrillation and, consequently, sudden cardiac death. Ventricular tachycardia is a ventricular rhythm with a heart rate of 120-250 per minute, consisting of three or more consecutive ventricular complexes. The ventricular complex is usually wide, deformed, AV dissociation is often detected, sometimes retrograde activation of the atria with 1:1 conduction. The most unfavorable course of ventricular tachycardia occurs in newborns, patients with long QT syndrome, organic heart diseases. In the absence of organic pathology, the course of arrhythmia in most cases is favorable for a long time, however, with prolonged persistence of ventricular tachycardia in childhood, an increase in hemodynamic disorders secondary to arrhythmia is recorded, which is associated with the development of circulatory failure and a worsening prognosis.

Epidemiology

For the pediatric population, ventricular tachycardia is a relatively rare arrhythmia. Its prevalence in childhood has not been studied. Among all arrhythmias in children, it occurs with a frequency of up to 6%. Ventricular tachycardia is related to SVT as 1:70.

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Causes of ventricular tachycardia

In children, ventricular tachycardia is often caused by organic heart disease: dilated cardiomyopathy, myocarditis, arrhythmogenic right ventricular dysplasia, heart tumors, ischemic lesions in patients with coronary artery origin anomalies, anatomical causes after surgical correction of congenital heart defects. Other causes of ventricular tachycardia may include pheochromocytoma, overdose of cardiac glycosides and antiarrhythmic drugs. In more than 70% of cases, ventricular tachycardia in children is considered idiopathic.

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Symptoms of ventricular tachycardia

The severity of clinical symptoms depends on the presence or absence of organic heart disease, age, clinical variant of ventricular tachycardia and properties of the electrophysiological substrate of arrhythmia. In patients with organic heart disease, tachycardia is usually accompanied by symptoms of circulatory failure; children feel interruptions in the heart area (non-paroxysmal ventricular tachycardia). Paroxysmal ventricular tachycardia is accompanied by sensations of heartbeats, discomfort in the chest, often weakness, dizziness, a feeling of fear; with a prolonged attack, symptoms of circulatory failure develop. In some cases, the attack is accompanied by loss of consciousness. Newborns often demonstrate tachypnea, shortness of breath, pallor or cyanosis of the skin, lethargy, weakness, enlarged liver and edema. Older children with idiopathic nonparoxysmal ventricular tachycardia are often asymptomatic or have minimal clinical manifestations despite the presence of nonparoxysmal sustained ventricular tachycardia. A high incidence of sudden death at a young age (under 40 years) has been reported in families of children with life-threatening arrhythmias.

Classification of ventricular tachycardia

Electrophysiological classification of ventricular tachycardia includes topical localization of arrhythmia (left ventricular, right ventricular, fascicular), its mechanism ( re-entry, ectopia, trigger activity) and morphology (monomorphic, polymorphic, bidirectional). According to Lown's classification, ventricular tachycardia should be classified into IVB-V gradations of ventricular rhythm disturbances. Clinical and electrocardiographic classification of ventricular tachycardia includes division into paroxysmal and non-paroxysmal; sustained and unstable (ventricular tachycardia lasting more than 30 s is considered sustainable, in pediatrics - more than 10 s); polymorphic (several morphologies of the ventricular complex) and monomorphic; idiopathic (in the absence of signs of structural heart pathology and clinical syndromes) and VT due to organic myocardial damage; relatively hemodynamically stable and unstable; right and left ventricular.

Ventricular fibrillation is a chaotic, asynchronous excitation of individual muscle fibers or small groups of fibers. This life-threatening ventricular arrhythmia leads to cardiac arrest and cessation of blood circulation.

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Diagnosis of ventricular tachycardia

Electrocardiographic signs of ventricular tachycardia are quite specific. The tachycardia rhythm exceeds the sinus rhythm by at least 10%. The width of the ventricular complex in newborns and young children is 0.06-0.11 s, and in children over 3 years old - always more than 0.09 s. The QRS morphology always differs from that in sinus rhythm with normal conduction to the ventricles and, as a rule, coincides with theQRS morphology of ventricular extrasystoles. The P wave can be detected in three variants:

• negative retrograde, following the QRS complex;
• not defined;
• normal sinus with a frequency less frequent than ventricular complexes. The RR interval is regular, but may be irregular in sinus "captures".

Silks and Garson proposed criteria for the "preferential" diagnosis of ventricular tachycardia in childhood:

• the presence of AV dissociation, which is present in most children with ventricular tachycardia;
• in the presence of 1:1 retrograde atrial activation, the P wave follows each QRS complex;
• periodically record fusion complexes or sinus captures;
• The tachycardia rhythm frequency is 167-500 per minute and should not exceed 250 per minute.

ECG criteria for ventricular fibrillation are continuous waves of various shapes and amplitudes with a frequency of 200-300 per minute (large-wave fibrillation) or 400-600 per minute (small-wave fibrillation). Electrophysiologically, the myocardium in ventricular fibrillation is fragmented into many zones that are in different phases of excitation and recovery of electrical activity.

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Treatment of ventricular tachycardia

Children with hemodynamically unstable ventricular tachycardia, persistent paroxysmal ventricular tachycardia, and ventricular fibrillation require emergency treatment. Lidocaine is administered intravenously slowly at a dose of 1 mg/kg every 5 minutes (maximum 3 administrations) or in a solution of 20-50 mcg/kg per minute until a clinical effect occurs. Amiodarone (intravenously slowly, then by drip at a dose of 5-10 mg/kg) and magnesium sulfate (intravenously 25-50 mg/kg once) are also used. Resuscitation measures should preferably be performed under the control of ECG data.

In cases of ineffectiveness of emergency antiarrhythmic therapy of ventricular tachycardia, increasing heart failure, cardioversion is indicated. In children, it is performed with an initial discharge of 2 J/kg, if the paroxysm persists, the discharge is increased to 4 J/kg. After some time, the discharge of 4 J/kg can be repeated.

Procainamide and propranolol are used to stop paroxysms of ventricular tachycardia in children. In children with fascicular ventricular tachycardia, class IV antiarrhythmic drugs are effective in stopping paroxysms of tachycardia. Children with non-paroxysmal sustained ventricular tachycardia in the absence of central hemodynamic disturbances require continuous antiarrhythmic therapy with drugs of classes I-IV. In case of monomorphic ventricular tachycardia, monotherapy with one of the antiarrhythmic drugs is used to restore the rhythm. It should be taken into account that in childhood, the incidence of side effects and complications, including proarrhythmic effects, is higher than in adults. This dictates the need for a thorough assessment of the indications and the use of concomitant metabolic and vegetotropic therapy. Indications for interventional treatment are the presence of clinical symptoms and signs of myocardial dysfunction in the patient. In cases where interventional treatment is not possible (increased risk of intraoperative complications), antiarrhythmic drugs are prescribed. In paroxysmal forms of ventricular tachycardia, interventional treatment methods are preferable.

In case of ventricular tachycardia developed as a result of myocarditis or autoimmune myocardial damage, a single course of anti-inflammatory/immunosuppressive therapy with prednisolone is administered. Courses of treatment with NSAIDs, metabolic drugs and antioxidants are prescribed. Antiarrhythmic therapy is administered similarly to the treatment of monomorphic ventricular tachycardia in children without organic myocardial damage. In order to improve hemodynamic parameters in chronic circulatory failure, ACE inhibitors are used.

If ventricular tachycardia is complicated by the development of pulmonary edema, syndromic therapy is carried out and anticoagulants are prescribed.

The development of syncopal attacks during therapy, critical sinus bradycardia, limiting the possibilities of subsequent antiarrhythmic therapy, as well as the persistence of a high risk of sudden cardiac death during treatment (assessed by the concentration of individual risk factors) require interventional treatment.

Prognosis of ventricular tachycardia

The prognosis for children with monomorphic ventricular tachycardia in the absence of organic pathology is relatively favorable. In the presence of organic changes in the cardiovascular system, the prognosis of ventricular tachycardia depends on the results of treatment of the underlying disease and arrhythmia control. In polymorphic ventricular tachycardia, the long-term prognosis is assessed as unfavorable, but the introduction of interventional treatment methods into practice allows increasing the reserves of therapy. In children with CYMQ-T, the prognosis depends on the molecular genetic variant of the disease and the effectiveness of complex therapy in terms of reducing the number and severity of modifiable risk factors for syncope and sudden cardiac death.