The purpose of this study was to evaluate the safety and efficacy of the EnTrust ICD device. A feature of this device allows it to send small, painless electrical impulses (Anti-tachycardia pacing or ATP) to the heart instead of shocking it out of a rhythm that is too fast. Stopping a dangerous heart rhythm this way does not cause any pain whereas a shock to the heart can feel like a punch in the chest. This device also allows the heart to beat on its own when it can and helping it (by pacing, or sending it electrical signals) when it needs help. This feature is important because previously studies have shown that pacing the heart too often can increase the risk for heart failure or for atrial fibrillation (having too rapid of heart beats in the atrium).