Cardiac arrhythmias in childhood. Diagnostic considerations and treatment.

Determining safe and effective antiarrhythmic therapy in paediatric patients requires definition of the mechanism of the arrhythmia, determination of associated risk factors for treatment (such as the presence of congenital cardiac defects, myocarditis or cardiomyopathy), and monitoring for potential drug side effects related to the treatment. A number of modalities for non-invasive evaluation of arrhythmias is available, including ECG, 24-hour ambulatory Holter monitoring, and transtelephonic ECG transmission. Arrhythmias requiring medical treatment in children with normal cardiac anatomy and function include supraventricular tachycardia (SVT), ventricular tachycardia (VT) and primary atrial tachycardias. SVT is treated acutely with vagal manoeuvres or drugs which slow AV conduction [adenosine (adenine riboside), edrophonium, phenylephrine or verapamil]. When medical conversion is not achieved, transoesophageal overdrive pacing or direct current (DC) cardioversion may be required. Long term drug therapy for SVT includes first-line treatment with digoxin, verapamil or propranolol. Ventricular tachycardia is managed acutely with DC cardioversion and intravenous lidocaine (lignocaine). Chronic drug regimens include mexiletine, propranolol or amiodarone. In children with structural congenital heart disease or myocardial dysfunction, hazards of drug therapy for arrhythmias include depression of cardiac function, proarrhythmia (drug-induced worsening of arrhythmias), and conduction abnormalities. Care must be taken to choose medication regimens which are likely to be effective with minimum risk of potentiating abnormal haemodynamics or conduction.