Ventricular tachycardia in children: symptoms, diagnosis, treatment

Ventricular tachycardia occupies a special place in arrhythmology, as it has a wide variability in clinical manifestations and, in some cases, a high probability of an unfavorable prognosis. Many ventricular tachycardias are associated with a high risk of ventricular fibrillation and, consequently, sudden cardiac death. Under ventricular tachycardias, a ventricular rhythm with a heart rate of 120-250 per minute is taken, consisting of three or more consecutive ventricular complexes. Ventricular complex, as a rule, wide, deformed, often reveal AV-dissociation, sometimes retrograde atrial activation with 1: 1. The most unfavorable course of ventricular tachycardia occurs in newborns, patients with the syndrome of prolonged Q-T interval, organic heart diseases. In the absence of organic pathology, the course of arrhythmia in most cases is long enough favorable, however, with prolonged retention of ventricular tachycardia in childhood, an increase in secondary hemodynamic disturbances in relation to arrhythmia is registered, which is associated with the development of circulatory insufficiency and a worsening of the prognosis.

Epidemiology

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

[1], [2], [3], [4], [5], [6]

Causes of ventricular tachycardia

In children, ventricular tachycardias are often caused by organic heart lesions: dilated cardiomyopathy, myocarditis, right ventricular arrhythmogenic dysplasia, cardiac tumors, ischemic lesions in patients with coronary artery abnormalities, anatomical causes after surgical correction of congenital heart defects. Among other causes of ventricular tachycardia may be pheochromocytoma, an overdose of cardiac glycosides and antiarrhythmic drugs. More than 70% of cases of ventricular tachycardia in children are regarded as idiopathic.

[7], [8], [9], [10], [11], [12], [13], [14]

Symptoms of ventricular tachycardia

The severity of clinical symptoms depends on the presence or absence of organic cardiac pathology, age, clinical variant of ventricular tachycardia, and the properties of the electrophysiological substrate of arrhythmia. In patients with organic heart lesions, tachycardia, as a rule, is accompanied by symptoms of circulatory insufficiency, children experience irregularities in the heart (non-paroxysmal ventricular tachycardia). Paroxysmal ventricular tachycardia is accompanied by palpitations, the appearance of discomfort in the chest, often weakness, dizziness, a sense of fear, with a prolonged seizure develop symptoms of circulatory insufficiency. In some cases, the attack is accompanied by loss of consciousness. Newborns often demonstrate tachypnea, dyspnea, pallor or cyanosis of the skin, lethargy, weakness, enlargement of the liver and edema. Older children suffering from idiopathic non-paroxysmal ventricular tachycardia often do not experience symptoms or, despite having a non-paroxysmal stable ventricular tachycardia, have minimal clinical manifestations. In families of children with life-threatening arrhythmias, a high incidence of sudden death occurred in young (up to 40 years) age.

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, bi-directional). According to Laun's classification, ventricular tachycardia should be attributed to IVB-V gradations of ventricular rhythm disturbances. Clinico-electrocardiographic classification of ventricular tachycardias includes a division into paroxysmal and non-paroxysmal; stable and unstable (a sustained ventricular tachycardia lasting more than 30 s, in pediatrics - more than 10 s); polymorphic (several morphologies of the ventricular complex) and monomorphic; idiopathic (in the absence of signs of structural pathology of the heart and clinical syndromes) and VT against the background of organic damage to the myocardium; relatively hemodynamically stable and unstable; right and left ventricular.

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

[15], [16], [17], [18], [19], [20]

Diagnosis of ventricular tachycardia

Electrocardiographic signs of ventricular tachycardia are quite specific. The rhythm of tachycardia exceeds the sinus frequency by at least 10%. The width of the ventricular complex in newborns and young children is 0.06-0.11 s, and in children older than 3 years - always more than 0.09 s. The morphology of QRS is always different from that of sinus rhythm with normal ventricular conduction and, as a rule, coincides with the QRS morphology of ventricular extrasystoles. The identification of the tooth P is possible in three versions:

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

Silks and Garson proposed criteria for a "primary" diagnosis of ventricular tachycardia in childhood:

• The presence of AV dissociation present in most children with ventricular tachycardia;
• in the presence of retrograde atrial activation 1: 1, the P tooth follows each QRS complex;
• periodically record downcomers or sinus captures;
• the frequency of the rhythm of tachycardia 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 a number of zones located in different phases of excitation and restoration of electrical activity.

[21], [22], [23], [24]

Treatment of ventricular tachycardia

Children with hemodynamically unstable ventricular tachycardia, stable paroxysmal ventricular tachycardia and ventricular fibrillation are in urgent need of therapy. Lidocaine is administered iv slowly in a dose of 1 mg / kg every 5 minutes (maximum - 3 injections) or in a solution of 20-50 μg / kg per minute until the appearance of a clinical effect. Apply also amiodarone (iv slowly, then drip in a dose of 5-10 mg / kg) and magnesium sulfate (iv in 25-50 mg / kg once). Conducting resuscitation is desirable under the control of ECG data.

In cases of ineffectiveness of emergency antiarrhythmic therapy of ventricular tachycardia, an increase in heart failure, cardioversion is indicated. Her children spend with an initial discharge of 2 J / kg, while maintaining paroxysmal discharge increase to 4 J / kg. After a while, you can repeat the discharge of 4 J / kg.

To relieve paroxysms of ventricular tachycardia in children, procainamide and propranolol are used. In children with fascicular ventricular tachycardia, with the arrest of paroxysm of tachycardia, class IV antiarrhythmics are effective. Children with non-paroxysmal resistant ventricular tachycardia in the absence of a violation of central hemodynamics require ongoing antiarrhythmic therapy with I-IV classes. In monomorphic ventricular tachycardia, monotherapy with one of the antiarrhythmic drugs is used to restore the rhythm. It should be borne in mind 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 evaluation of the indications and the use of concomitant metabolic and vegetotropic therapy. Indications for interventional treatment are the patient's clinical symptoms and signs of myocardial dysfunction. In cases of impossibility to resort to interventional treatment (increased risk of intraoperative complications), antiarrhythmic drugs are prescribed. In paroxysmal forms of ventricular tachycardia, interventional treatment methods are preferred.

In ventricular tachycardia, which has developed as a result of myocarditis or autoimmune lesions of the myocardium, a single course of anti-inflammatory / immunosuppressive therapy with prednisolone is carried out. Prescribe courses of treatment for NSAIDs, metabolic drugs and antioxidants. Antiarrhythmic therapy is similar to treatment of monomorphic ventricular tachycardia in children without organic myocardial damage. To improve hemodynamic parameters in chronic circulatory failure use ACE inhibitors.

In case of complication of ventricular tachycardia, the development of pulmonary edema is followed by syndromic therapy, and anticoagulants are prescribed.

The development of syncope attacks on the background of therapy, a critical sinus bradycardia, limiting the possibility of subsequent antiarrhythmic therapy, and the preservation of a high risk of sudden cardiac death (assessed by the concentration of individual risk factors) require interventional treatment.

Prognosis of ventricular tachycardia

The prognosis in 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 the control of arrhythmia. With polymorphic ventricular tachycardia, the long-term prognosis is regarded as unfavorable, but introduction of interventional methods of treatment into practice allows to increase 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.