Data-driven Decisions: The Importance of Clinical Trials in Arrhythmia Management

As a result of clinical trials, the measurement of arrhythmias has evolved over the past three decades. In the late 1960s, customary teaching was that ventricular premature depolarizations were dangerous and antiarrhythmic therapy, in hopes of reducing fatal consequences, became common place; however, following clinical trials such as CAST, IMPACT, and SWORD, we learned that, at least in postinfarct patients, arrhythmia suppression may lead to increased rather than reduced mortality. Such trials have led to a marked reduction in therapy of indiscriminate ventricular ectopy and have led to ongoing testing of specific subgroups identified as having particularly higher adverse prognostic risk. With the advent of cardiac monitoring and the confirmation that ventricular tachyarrhythmias are the most common cause for sudden death, their therapy, too, has evolved and matured, again aided by clinical trials. The ESVEM study prospectively examined the role of monitor-guided versus electrophysiologically guided drug therapy of ventricular tachyarrhythmias and confirmed that both approaches may have a role in reducing arrhythmic deaths-though the specific benefits of each technique remain somewhat unsettled. Both the ESVEM and CASCADE studies suggested that the most effective drugs for ventricular tachyarrhythmias are the class II/III drugs, sotalol and amiodarone, both appearing more effective than our older class I agents. These should now be viewed as the first-line drugs for these arrhythmias. The relative benefits of these two agents with respect to each other and to implantable cardioverter defibrillators, however, remains to be determined by further clinical trials, such as AVID and CIDS. The therapy of atrial tachyarrhythmias has similarly evolved with the aid of clinical observations. While rate control is required in all patients with atrial fibrillation, we have come to realize that the applications of antiarrhythmic drugs for the purpose of maintaining sinus rhythm must be used only selectively rather than uniformly. Both a meta-analysis by Coplen and colleagues and a report by the SPAF investigators suggested that with atrial arrhythmias, too, antiarrhythmic drug therapy may result in enhanced rather than reduced mortality in some circumstances. Additional clinical trials are needed to further elucidate the role of antiarrhythmic therapy of atrial fibrillation.