Other primary prevention trials-what is clinically and economically necessary?

There are a number of important primary prevention implantable cardioverter defibrillator (ICD) trials underway which will help define the role of the ICD in high risk patients. High risk is defined by low ejection fraction, although a number of electrical markers (e.g., the signal averaged ECG and invasive electrophysiologic test) are also under evaluation. The trials currently underway (including SCD-HEFT, MADIT II, and the CABG-PATCH substudy) are analyzing patients with either coronary or idiopathic cardiomyopathy who have an EF of 35% or under. Patients are randomized to either ICD therapy or no antiarrhythmic drug therapy. Maximal congestive heart failure therapy with ACE inhibitors and beta blockers is used in both arms of each trial. At the conclusion of these trials we should have a better understanding of which group of presumably high risk patients, if any, will benefit from the ICD. Another group of high risk patients that is being encountered more frequently: those who have a high risk diagnosis. These patients are present in such small numbers that a large randomized trial is impossible. As many of these patients are receiving ICDs, a national registry of firing rates will be helpful.