Prediction and prevention of sudden cardiac death in heart failure

The definition of sudden cardiac death (SCD) remains controversial. Many such deaths are not witnessed, and without cardiac monitoring at the time of death the assumption of an underlying arrhythmic cause is speculative. Nevertheless, it has been estimated that SCD accounts for 300 000 to 400 000 deaths annually in the USA.1 The degeneration of monomorphic ventricular tachycardia (VT) into ventricular fibrillation (VF) accounts for the majority of sudden arrhythmic deaths.w1 Despite considerable advances in the treatment of heart failure over the past 20 years, morbidity and mortality remain high with a four year survival of less than 50% in population based studies (fig 1). Ventricular arrhythmias (including non-sustained VT) have been documented in up to 85% of patients with severe congestive heart failure.2 Figure 1  Cumulative survival of 552 incident (new) cases of heart failure identified in the London heart failure studies 1995 to 1998. Kaplan-Meier estimates with 95% point wise confidence bands (authors’ own data). The implantable cardioverter-defibrillator (ICD) is highly effective at terminating life threatening ventricular tachyarrhythmia (fig 2). In selected high risk patients ICDs have proven to be a cost effective method of reducing mortality. At present, 1–2% of the population has heart failure and numbers continue to increase,3 but the ICD remains expensive. The challenge lies in identifying patients with heart failure who are at significant risk of arrhythmia and who would benefit from an ICD in addition to other antiarrhythmic strategies. Figure 2  Implantable cardioverter-defibrillator (ICD) data showing an episode of ventricular fibrillation terminated by a 21 J shock delivered by the device. Intracardiac electrograms are recorded from the right atrium (A) and right ventricle (V) along with a surface ECG. Sensed intracardiac intervals are shown at the bottom of the figure. Following cardioversion, ventricular fibrillation is terminated and bradycardia is seen requiring atrioventricular …