Compared with S-ICDs, single chamber T-ICDs weigh approximately one-half as much, have a longer battery life, and they defibrillate transvenously with ≤40 J. Unlike the S-ICD, the tiered therapy T-ICD provides 3 functions, namely defibrillation, ATP, and bradycardia pacing. A large proportion of ICD patients have VT that can be terminated painlessly by ATP. Twenty years ago, a pivotal study of tiered therapy ICDs concluded that the “most important advance in device therapy is the option to treat monomorphic ventricular tachycardia with antitachycardia pacing maneuvers” (3). Without ATP, a conscious patient will receive painful 80-J shocks for VT. But it is often difficult to determine which primary prevention patients will develop VT. In the MADIT-II (Multicenter Automatic Defibrillation Trial), 25% of patients—who were not inducible in the electrophysiological testing arm—experienced a clinical VT episode within the first 3 years after implant (4). Indeed, in the S-ICD IDE study, even though patients with known pace-terminable VT were excluded, 18 of 28 patients (64%) who had a spontaneous VT/VF event during follow-up received an 80-J shock for monomorphic VT. Moreover, although controversial, current data suggest that all T-ICD shocks, both appropriate and inappropriate, might be associated with reduced longevity and quality of life (5). Thus, ATP might confer important advantages that are not available in shock-only devices.