 1. This study will be a randomized comparison of bipolar and extended bipolar sensing. As per usual standard of care, at the end of ICD implantation two sensing tests in VF will be performed. Patients will be randomized to sensing in VF through the device. Each patient will undergo testing in one randomized configuration followed by a second test in the other configuration. After testing at the time of implant, each patient will be seen at one month in follow up. Sensing of each configuration will be reevaluated at that time in sinus rhythm. 