Prevention of arrhythmic death in valvular heart disease: Beware the implantable defibrillator paradox

摘要

Clinicians caring for patients with valvular heart disease (VHD) at risk for arrhythmic sudden cardiac death (SCD) face a challenge in determining the benefit of implantable cardioverter defibrillators (ICD). Prevention of SCD in patients with VHD is not specifically addressed in the 2008 Guidelines for Device-Based Therapy of Cardiac Rhythm.1 Clinicians might be guided by the secondary prevention Class I recommendation for patients who are survivors of cardiac arrest because of ventricular fibrillation (VF) or hemodynam-ically unstable ventricular tachycardia (VT) in the absence of reversible causes (Level of Evidence A) or spontaneous VT (Level of Evidence B).1 Another Class I indication for ICD implantation is syncope of undetermined origin with clinically relevant, hemodynamically significant sustained VT or VF induced at electrophysiologic study (Level of Evidence B). These recommendations are principally based on 3 secondary prevention randomized clinical trials: Antiar-rhythmics Versus Implantable Defibrillators (AVID), Cardiac Arrest Study Hamburg (CASH), and Canadian Implantable Defibrillator Study (CIDS).1 If the results apply to VHD, clinicians can inform their patients that they can expect 28% relative risk reduction in all-cause mortality because of a 50% relative risk reduction in arrhythmic death.1 However, the majority of patients in these trials had ischemic heart disease (75-85%) or nonischemic dilated cardiomyopathy (DCM, 10%-15%). Very few of the patients had VHD. Only the CIDS trial provides the proportion of patients with VHD (2%). The CASH trial included 4% of patients with "other" forms of structural heart disease and the AVID trial does not indicate that any patients had VHD. There is therefore scarce evidence that ICD therapy is useful for secondary prevention in patients with VHD.