Are Implantable Cardioverter Defibrillator Shocks a Surrogate for Sudden Cardiac Death in Patients With Nonischemic Cardiomyopathy?

Abstract

Appropriate ICD shocks occur more frequently than SCD in patients with nonischemic cardiomyopathy. This suggests that episodes of nonsustained ventricular tachycardia frequently terminate spontaneously in such patients.

Evidence regarding clinical use of microvolt T-wave alternans

“…This result is consistent with the reports of other investigators who have also found that the number of AICDTs greatly exceeds the ICD mediated reduction in deaths in clinical ICD trials 16,17 . One explanation for the excess number of AICDTs is that ICDs treat arrhythmias that would have self-terminated had no ICD been implanted.…”

“…Recent analyses of ICD trials 16,17 have concluded that AICDTs in the ICD arms of the studies exceeded sudden deaths in the control arms by a factor of two to three. These analyses raise questions about the suitability of AICDT as a surrogate endpoint for SCD in clinical trials 18 .…”

Safety Aspects of Implantable Cardioverter Defibrillators in Patients Participating in Exercise Therapy: A Systematic Review and Meta-Analysis

“…Clinical outcomes also varied in reporting and definition. ICD shocks and ATP therapy, although associated with adverse events, may not be surrogate for sudden cardiac death [41]. Significant variation in ICD programming exists and was not acknowledged or discussed in most studies.…”

Prognostic Importance of Defibrillator Shocks in Survivors of Sudden Cardiac Death

“…In the Pain FREE Rx II trial [19], majority of the monomorphic VT terminated spontaneously before ATP, confirming the fact that not all ventricular arrhythmias require electrical conversion therapy. Also, the number of shocks -whether appropriate or inappropriate -may not be correlated with rates of mortality [20]. Therefore mere counting of shocks does not indicate a life saved.…”