Prevention of sudden cardiac death.

It is often unclear why some patients suffer sudden cardiac death (SCD), or even what risk factors correlate best with the syndrome. This review describes current thinking on the prevention of SCD. Most studies have focused on the prevention of potentially fatal ventricular arrhythmias in patients post myocardial infarction (MI). While pharmacotherapy has a role in the prevention of SCD in patients post MI, the interpretation of drug trials can be problematic. This is because not all patients participating in such trials received optimized medical therapy by today's standards. As a result, trial outcomes for new therapies may not reflect their true efficacy when they are added to a background of best medical care. The two principal prophylactic modalities for SCD studied to date are antiarrhythmic drug therapy and use of an implantable cardioverter defibrillator (ICD). At the present time, antiarrhythmic drugs, such as the class III agent amiodarone, seem to display relatively limited efficacy for the primary prevention of sudden death in most patients post MI. Most clinical trials have found that ICD therapy has a significant mortality benefit in patients at high risk for ventricular arrhythmias. This has been demonstrated in primary prevention trials, and in secondary prevention trials such as Antiarrhythmics Versus Implantable Defibrillators (AVID), which studied patients who survived a near-fatal ventricular arrhythmia. Based on an analysis of secondary prevention trials, the single patient characteristic that best predicted an advantage of ICD therapy over antiarrhythmic drug therapy was a left ventricular (LV) ejection fraction < or = 35%. Cardiac resynchronization therapy has been established as having a mortality benefit in patients with dyssynchronous LV contraction associated with dilated cardiomyopathy.