Can implantable defibrillators reduce non-arrhythmic mortality?

Several authors have made the intriguing observation that Implantable Cardioverter Defibrillators (ICD) appear not only to reduce sudden deaths, but also mortality due to non-arrhythmic causes. Studies have shown that this observation can not be attributed to patient selection bias. In trying to explain this apparent anomaly, it should be noted that two treatment strategies are being compared. Thus, it might be that, under certain circumstances, antiarrhythmic drugs contribute to non-arrhythmic deaths, not that ICDs reduce them. There appear to be some plausible explanations for this phenomenon, e.g., the long-term effect on cardiac function of episodes of ventricular tachycardia lasting for several hours for patients treated solely by antiarrhythmic drugs, compared to their quick termination by an ICD. However, further research into this curious mode of death issue is needed, and may provide further insights into patient populations deriving greatest benefit from one therapy or the other.