DEfibrillators To REduce Risk by MagnetIc ResoNance Imaging Evaluation

Detailed Description:

The utilization of ICD therapy has resulted in significant reduction in mortality among those at highest risk of sudden cardiac death, such as survivors of cardiac arrest and patients presenting with symptomatic sustained ventricular arrhythmias. Patients with CAD and advanced LV dysfunction (EF <35%) also benefit from ICD. However, although at high risk, these patients represent only a small percentage of the population who die suddenly. While there are many tests that have been used for stratification of risk for sudden cardiac death, the two that have documented clinical utility are determination of left ventricular ejection fraction and presence of inducibility of ventricular tachycardia during programmed electrical stimulation performed as part of EP testing. The utility of these tests likely result from their ability to select patients who have the requisite substrate allowing for sustained ventricular tachyarrhythmias. It has been shown that ventricular tachycardia occurs more commonly in the setting of larger infarcts. Ejection fraction has been related to infarct size; presumably, the larger the area of infarction, the lower the ejection fraction. Electrophysiologic testing directly establishes the presence of substrate by the actual induction of ventricular tachycardia.

A major limitation of electrophysiologic programmed stimulation is the high number of false negative findings. Thus, a significant number of patients without inducible arrhythmias remain at risk. CE-MRI provides functional information (EF, LV Volumes, LV mass, etc), which is routine in the initial evaluation of post-MI patients, and in addition provides detailed geometry of scar tissue. There is a clear association between inducible arrhythmias and scar size which until the development of cardiac MRI, could not be seen in humans. Use of cardiac MRI has demonstrated that although most patients with a large MI were inducible, a small but significant number of patients, who remain at risk, were not inducible. There was also an association between death and infarct size in patients with cardiovascular risk factors but no established CAD.

The Center for Medicare Services (CMS) has recently decided in a coverage decision that patients with left ventricular dysfunction, heart failure, and an ejection fraction of <35% would be eligible to receive an ICD as long as they are enrolled in a prospective registry. Patients with LV ejection fractions greater than 35% or those without heart failure and ejection fractions over 30%, represent a more difficult management dilemma. However, since the majority of out of hospital cardiac arrests occur in patients with EF >35%, managing these patients is crucial in addressing the epidemiologic problem of sudden cardiac death.

The primary objective of this trial is to test the hypothesis that therapy with an ICD combined with medical therapy improves long-term survival compared to medical therapy alone in patients with CAD, infarct mass greater than or equal to 10% of the left ventricle and left ventricular dysfunction who do not have an indication for ICD by either of the following criteria. Patients must have an EF of >35% or have an EF of 30-35% and must not have inducible ventricular tachycardia or have NYHA Class II or greater heart failure (Target Population).