Treatment of supraventricular tachyarrhythmias

Emergency treatment of paroxysmal supraventricular tachycardia is aimed at interrupting the paroxysm of tachycardia and normalizing hemodynamics.

Stopping an attack begins with vagal tests: turning upside down, handstand, Aschner's test, Valsalva's test, carotid sinus massage, pressing on the root of the tongue. In young children, turning upside down for several minutes is most effective.

The tactics of emergency drug therapy depends on the electrophysiological substrate of paroxysmal supraventricular tachycardia. Emergency therapy of paroxysmal supraventricular tachycardia with a narrow QRS complex, as well as with a wide QRS due to functional blockade of the His bundle branches, begins with intravenous administration of adenosine phosphate (1% solution intravenously by jet stream: up to 6 months - 0.5 ml, from 6 months to 1 year - 0.8 ml, from 1 year to 7 years - 1 ml, 8-10 years - 1.5 ml, over 10 years - 2 ml). If ineffective, the administration can be repeated twice more with an interval of at least 2 minutes. Adenosine phosphate slows conduction through the AV node, interrupts the re-entry mechanism and helps restore sinus rhythm. The drug may cause cardiac arrest, so it should be administered under conditions that allow resuscitation if necessary. If triple administration of adenosine phosphate is ineffective, class IV antiarrhythmic drug verapamil (0.25% solution intravenously slowly at a dose of 0.1-0.15 mg/kg) is administered. If tachycardia persists, intravenous administration of class III drug amiodarone is recommended. The drug is very effective in preventing the development and stopping ventricular fibrillation. It has a long half-life (from 2 to 10 days). The peak concentration of the drug in the blood is reached within 30 minutes. If necessary, the drug can be administered over several days (no more than 5 days). In paroxysms of atrial flutter, ectopic and ge-entry atrial tachycardia, orthodromic AV reciprocating tachycardia, the attack can be stopped in older children (7-18 years) by administering procainamide, which belongs to class 1a antiarrhythmic drugs (10% solution intravenously slowly at a dose of 0.1-0.2 ml/kg). The administration is carried out under the control of ECG and blood pressure data and is stopped in case of a sharp drop in blood pressure, the appearance of progressive expansion of the ventricular complex on the ECG. If conditions are present, it is possible to stop the attack by radiofrequency catheter destruction of the arrhythmogenic zone. This type of non-drug treatment is carried out in an X-ray operating room.

Emergency antiarrhythmic therapy for paroxysmal supraventricular tachycardia with a wide QRS complex (antidromic tachycardia) includes class I drugs (procainamide) and ajmaline, which is similar in electrophysiological properties. It reduces the rate of depolarization, increases the duration of repolarization, refractory periods in the atria, ventricles, and accessory conduction pathways [2.5% solution intravenously at a dose of 1 mg/kg (1-2 ml) slowly over 7-10 min in 10 ml of isotonic sodium chloride solution]. The drugs are administered under the control of ECG and blood pressure data; administration is stopped when progressive intraventricular conduction delay and the ECG phenotype of Brugada syndrome appear. Long-term hemodynamically significant antidromic paroxysmal supraventricular tachycardia, as well as attacks of atrial flutter with conduction through additional atrioventricular connections are indications for emergency radiofrequency catheter destruction of the abnormal additional AV connection.

In order to create favorable conditions, from the point of view of neurogenic rhythm regulation, for drug-induced relief of tachycardia paroxysm, sedatives, aminophenylbutyric acid (tranquilizer phenibut, which has a sedative, anxiolytic effect and has elements of nootropic activity) and carbamazepine (has an antidepressant, membrane-stabilizing and antiarrhythmic effect due to inactivation of the incoming sodium current) are prescribed immediately upon the development of the paroxysm. The prescription of these drugs is especially important in cases where tachycardia attacks in children are accompanied by pronounced psychoemotional arousal and have a vegetative coloring. In case of a long, protracted attack, the administration of diuretics is recommended. In cases of ineffectiveness of complex drug therapy, the increase in heart failure, the implementation of increasing transesophageal stimulation and cardioversion up to 2 J/kg is indicated.

Rational therapy of paroxysmal supraventricular tachycardia in the interictal period affects the neurogenic basis of arrhythmia, promoting the restoration of neurovegetative balance in the regulation of the heart rhythm. Nootropic and nootropic-like drugs [gamma-aminobutyric acid (aminalon), glutamic acid] have a trophic effect on the vegetative centers of regulation, promote increased metabolic activity of cells, mobilization of energy reserves of cells, regulation of cortical-subcortical relationships, and have a soft and persistent stimulating effect on the sympathetic regulation of the heart. In case of psychoemotional disorders, aminophenylbutyric acid (phenibut) is prescribed, which has a sedative, anxiolytic effect and has elements of nootropic activity. In paroxysmal supraventricular tachycardia in children, long-term administration of classical antiarrhythmic drugs has significant limitations and adversely affects the long-term prognosis of paroxysmal supraventricular tachycardia.

In cases where tachycardia is persistent and there is a need to connect classical antiarrhythmic drugs, radiofrequency catheter ablation becomes the method of choice. In determining the indications, one should adhere to reasonable conservatism in young children, which is associated with a high probability of spontaneous disappearance of rhythm disturbance by 8 months of age. However, in 30% of them, arrhythmia subsequently recurs, which leads to the need for observation and decision-making on further treatment tactics. In children under 10 years of age, the risk of complications during interventional treatment is higher than in the older age group. In children over 10 years of age, indications for interventional methods of treating tachyarrhythmias are comparable to those for adult patients. The effectiveness of radiofrequency ablation of supraventricular tachycardias, according to various authors, ranges from 83 to 96% and depends on the type of arrhythmia, technical capabilities and experience of the clinic. In case of frequent paroxysmal supraventricular tachycardia (monthly attacks) and impossibility of conducting interventional treatment of arrhythmia (young patient, localization of electrophysiological substrate in close proximity to the structures of the cardiac conduction system or epicardial), a persistent antiarrhythmic effect can be provided by the anticonvulsant drug carbamazepine (at a dose of 5-10 mg/kg per day in 2-3 doses for a long time), which has an antidepressant, membrane-stabilizing and antiarrhythmic effect due to inactivation of the incoming sodium current. In preschool-aged children, with the persistence of frequent and/or hemodynamically unstable attacks of paroxysmal supraventricular tachycardia against the background of drug basic therapy and the ineffectiveness of carbamazepine (finlepsin), a course of antiarrhythmic drugs is possible: amiodarone or propafenone.

The goals of rational drug therapy of non-paroxysmal supraventricular tachycardia are correction of neurovegetative disorders that contribute to the functioning of abnormal electrophysiological mechanisms of myocardial excitation (basic therapy) and direct impact on the electrophysiological substrate of arrhythmia (antiarrhythmic drugs). Basic therapy helps restore the protective function of the sympathetic-adrenal system and has a trophic effect on the autonomic regulation centers, restoring the balance of autonomic regulation of the heart rhythm, shifted in children with non-paroxysmal supraventricular tachycardia towards the relative predominance of parasympathetic influences. For this purpose, children with non-paroxysmal supraventricular tachycardia are prescribed nootropic and vegetotropic drugs with a stimulating component of action (gamma-aminobutyric acid (aminalon), glutamic acid, pyritinol (pyriditol)]. Neurometabolic stimulants have varying degrees of antiasthenic, sympathomimetic, vasovegetative, antidepressant and adaptogenic (improve tolerance to exogenous stressors) action. Children with non-paroxysmal supraventricular tachycardia are prescribed these drugs alternately for 2-3 months each (the total duration of the first course is 6 months). With a reliable decrease in the severity of arrhythmia after the first course, a repeated course is prescribed for 3 months. If signs of diastolic myocardial dysfunction are detected according to echocardiography data, disturbances in the process repolarization according to ECG data, stress tests, metabolic therapy is carried out. For this purpose, antihypoxants and antioxidants, vitamins and vitamin-like agents, macro- and microelements are prescribed: levocarnitine orally 50-100 mg / day for 1-2 months, kudesan orally 10-15 drops per day for 2-3 months, actovegin intramuscularly 20-40 mg for 5-10 days.

Indications for interventional treatment of children with non-paroxysmal supraventricular tachycardia are non-paroxysmal, recurrent (continuously recurrent) supraventricular tachycardias of various genesis with the development of arrhythmogenic myocardial dysfunction in children of any age with the ineffectiveness of drug therapy and the absence of contraindications to interventional therapy. Indications for the prescription of classical antiarrhythmic therapy (antiarrhythmic drugs of classes I-IV) are similar to those for interventional treatment. That is why the prescription of antiarrhythmic drugs is possible only in the presence of contraindications to interventional treatment. Methods of interventional treatment of supraventricular tachycardia are generally recognized. In children, it is important to use the most gentle protocol of radiofrequency effects.

In paroxysmal supraventricular tachycardia, the effectiveness of drug-based therapy is assessed no earlier than after 3-6 months. Positive dynamics in terms of symptoms appears consistently and has certain patterns. Initially, there is a change in the circadian pattern in the occurrence of tachycardia attacks: the most unfavorable night and evening paroxysms are replaced by daytime or morning ones. Then the nature of the relief of supraventricular tachycardia attacks changes: attacks that were previously relieved only by intravenous administration of antiarrhythmic drugs become susceptible to relief by vagal tests. And finally, there is a decrease in the duration and frequency of attacks, followed by the disappearance of paroxysms.

The effectiveness of radiofrequency catheter ablation is assessed intraoperatively based on special electrophysiological criteria, as well as in the early and late postoperative period based on the disappearance of attacks both in the early and late periods, and the impossibility of provoking the occurrence of a paroxysm of tachycardia of the previous morphology during a special protocol of transesophageal atrial stimulation. The study is carried out no earlier than 3 months after interventional treatment. In cases of interventional treatment, when acting in an area anatomically close to the structures of the normal cardiac conduction system, a complete transverse block may occur, which will lead to the need for implantation of an electric pacemaker. The probability of developing this complication with modern technologies for performing this procedure is low. When the electrophysiological substrate of supraventricular tachycardia is localized subepicardially, in close proximity to the structures of the main conduction system of the heart, coronary arteries, the procedure of radiofrequency catheter ablation may be regarded as inappropriate due to the risk of complications. In these cases, the main emphasis should be placed on drug therapy - a combination of basic and antiarrhythmic therapy; if such treatment is ineffective, the prognosis is regarded as unfavorable.