The purpose of this study is to determine how well the device predicts susceptability to potentially lethal ventricular arrhythmias.

Sudden cardiac death (SCD) accounts for half of all deaths from cardiovascular causes, with an annual incidence of 1 to 2 deaths per 1000 population. In the United States this translates to between 300,000 to more than 400,000 deaths annually. Results from numerous large, well designed clinical trials have demonstrated the efficacy of the implantable cardioverter-defibrillator (ICD) for improving survival in patients with ischemic heart disease. However, measures used to risk stratify patients, such as left ventricular ejection fraction do not adequately identify those patients who can most benefit from ICD therapy. As a result, many patients who currently receive an ICD do not use the device. In addition, many more patients who could benefit from ICD therapy are outside of current guidelines and do not have access to this life-saving therapy.

This prospective study was intended to determine how well the Harbinger Wedensky Modulation Index (WMI) technique risk stratifies patients into two groups: those needing antiarrhythmic therapy and those who do not need antiarrhythmic therapy.

Inclusion Criteria:

• Post myocardial infarction patients receiving ICD therapy

Exclusion Criteria:

• Patients unable to give consent
• Pacemaker dependant patients
• Pregnant women

Post myocardial infarction patients who received an ICD are included. Enrollment is at eight sites - four in the USA and four in three European countries. The enrollment sites are hospitals and teaching institutions.