Heart failure: the challenge of selecting patients for implantable cardioverter defibrillator therapy

Patients with heart failure die predominantly of progressive pump failure or sudden cardiac death. Therefore, it is attractive to believe that an implantable cardioverter defibrillator (ICD) will dramatically reduce mortality by reducing sudden death. However, unfortunately it is not that simple; sudden death is not the same as ICD-preventable death. While ICD prophylaxis always reduces arrhythmic death, it does not always reduce all-cause mortality due to competing risks. Importantly, an arrhythmia may be a marker for heart failure decompensation, with patients at increased risk of heart failure death following shock therapy. Randomized trials have now demonstrated the potential benefits of ICDs in selected patients with left ventricular dysfunction, yet they have also failed to demonstrate benefit in populations where one might have expected to see benefit (e.g., early post-myocardial infarction). Device therapy can offer heart failure patients much more than just a simple shock box. The addition of a left ventricular lead to allow biventricular pacing (cardiac resynchronization therapy) improves symptoms and prolongs life in selected patients with QRS prolongation. Newer technologies allow remote monitoring through the device, which offers the potential to recognize heart failure decompensation or arrhythmias early so that appropriate treatment can be instituted. However, deciding which patient should receive an ICD remains one of the most challenging questions in cardiovascular medicine.