In a recent retrospective review of the landmark 2002 Multicenter Automatic Defibrillator Implantation Trial (MADIT-2) trial, it was found that patients with a weak heart muscle caused by a prior heart attack or coronary artery disease who had an implantable cardioverter-defibrillator (ICD) installed were at increased risk of new or recurrent heart failure (usually manifested by fluid on the lungs, cough, shortness of breath or leg swelling) after the first delivery of an appropriate shock. On the other hand, the study found, inappropriate shocks (e.g., those delivered for upper chamber rhythms that caused the device to reach its rate cut-off for calling a heart rhtyhm abnormal) apparently doesn't increase later heart failure risk. According to Heartwire:
"Our interpretation of this is that the ICD shocks by themselves don't damage the heart and don't increase the risk of heart failure—it's the life-saving ICD therapy transforming the risk of sudden death into a subsequent heart-failure risk," according to Dr Ilan Goldenberg (University of Rochester, NY), lead author of the post hoc study from the second Multicenter Automatic Defibrillator Implantation Trial (MADIT-2).
Another major finding from the analysis, he told heartwire, is that HF risk started rising after appropriate-shock delivery by either single- or dual-chamber ICDs compared with nondevice conventional therapy. That appears to contrast with some earlier studies suggesting that dual-chamber ICDs, as compared with backup single-chamber devices, can promote heart failure. But Goldenberg said a subanalysis including only patients with ICDs showed dual-chamber devices accounted for "a little more" of the risk increase. ICD shocks by themselves don't damage the heart and don't increase the risk of heart failure—it's the life-saving ICD therapy transforming the risk of sudden death into a subsequent heart-failure risk.
Beta blockers they felt reduced the risk of hospitalization for heart failure significantly and doctors should be vigilant to watch for heart failure development in ICD patients who have suffered their first clinical shock. My experience has been that after an episode of recurrent appropriate ICD shocks, if we treat heart failure in many of these patients (especially with beta blockers), their shock frequency dramatically improves.
Whether biventricular pacing for heart failure (a newer technique that adds an additional lead to pace the left side of the main pumping chamber of the heart (the left ventricle) in tandum with the more conventional right ventricular lead installed with defibrillators and was found in other trials to reduce heart failure risk) should be considered in all patients is being studied now in the MADIT-3 trial. Stay tuned.
In short, if you have an ICD, its a good thing, you'll live longer. But there may be significant issues regarding heart failure development later if you need to use it.