 7. Exclusion criteria: age 18, inability to give informed consent, or life expectancy less than one year, pacemaker dependence, or use of preexisting lead for sensing, any condition which would preclude ICD testing at the end of the implant. Patients who are undergoing upgrade to an ICD from a pacemaker will also be excluded. In addition, patients with inherited arrhythmias or ion channel related arrhythmias will be excluded from the study. 