Ventricular arrhythmias, sudden death and heart failure

Despite therapeutic advances, the mortality rate associated with congestive heart failure remains as high as 20% per year. Among patients with severe left ventricular dysfunction, more than 60% of deaths result from ventricular tachycardia or fibrillation, 20% from bradyarrhythmias (including advanced atrio-ventricular block or asystole), and 20% from terminal ventricular pump failure. Ventricular arrhythmias and sudden death result from an interaction between a trigger and a substrate with neurohumoral factors (enhanced activity of the adrenergic and renin-angiotensin systems, electrolyte disturbances, etc.). Left ventricular structural lesions result in complex electrophysiological changes, but those mainly responsible for arrhythmias are conduction slowing, changes in the refractory period, inhomogeneous activation and repolarization, and abnormal automaticity It is important but difficult to identify those patients most at risk. According to current guidelines, most patients with left ventricular dysfunction (left ventricular ejection fraction below 35%) and symptomatic heart failure may qualify for prophylactic implantation of cardioverter defibrillators (ICD), which have been shown to reduce the risk of sudden cardiac death by 26% in randomized trials. The challenge is now to better identify and select patients who will benefit from implanted devices and resynchronization therapy. We review the literature and report our personal experience of the prognostic value of various Holter ECG parameters providing information on the autonomic nervous system (sinus variability, baroreflex sensitivity), repolarization dynamics (QT dispersion, T alternance, ventricular late potentials) and the results of programmed ventricular stimulation. Combining electrocardiographic stratification with etiologic and clinical information may help to select the best candidates for defibrillator implantation and resynchronization. These devices, combined with optimal pharmacologic treatment, have been shown to reduce overall mortality and sudden death in recent multicenter randomized controlled trials.