VENTRICULAR-TACHYCARDIA AND VENTRICULAR-FIBRILLATION

There is substantial interest in the association of ventricular tachyarrhythmias with the autonomic nervous system. Long QT syndrome has been proposed as a ''Rosetta Stone'' for the association between sympathetic nervous activity and genesis of ventricular tachyarrhythmias. Early afterdepolarizations, which can now be recorded in the clinical electrophysiology laboratory, may play an important role in repolarization abnormalities and the development of associated ventricular tachyarrhythmias. The response of the QT interval to exercise and other physical maneuvers is disturbed in congenital long QT syndrome and in patients who develop polymorphic ventricular tachycardia from class la antiarrhythmic drugs. Therefore it may be more important clinically to the dynamic rather than the resting behavior of the QT interval. Automatic analysis of the QT interval from ambulatory ECG recordings will provide new perspective. Patients with left ventricular dysfunction and a recent history of ventricular tachyarrhythmias have excessive cardiac norepinephrine spillover, and sympathetic nerve traffic is higher at the onset of a ventricular tachyarrhythmia. Excess catecholamine may induce the arrhythmia but may also help to preserve hemodynamic stability during the tachycardia by buffering the sudden fall of arterial pressure at the onset of arrhythmia. Antiadrenergic therapy prevents sudden death in post-myocardial infarction patients and in patients with prolonged ventricular depolarization. Other therapies have been disappointing. The combination of several low-dosage antiarrhythmic agents, particularly with amiodarone, may be worth considering for ventricular arrhythmias and poor left ventricular function. Full revascularization is known to reduce the incidence of sudden cardiac death. Coronary angioplasty may confer an antiarrhythmic benefit in selected cases, but more information is needed. Electric ablation using low-energy capacitor discharges has achieved some success in patients unsuited for surgery. This year there has been movement toward clinical modification of ventricular repolarization rather than conduction, the therapeutic modulation of the autonomic nervous system, and further refinement of nonpharmaceutical techniques.