Shock First or Pace First to Break Ventricular Tachycardia?

Implantable cardioverter-defibrillators (ICDs) decrease all-cause mortality in patients at high risk for ventricular arrhythmias, especially those with reduced left ventricular systolic function, and this mortality benefit is directly related to termination of these potentially life-threatening arrhythmias. Transvenous ICDs, which comprise an implanted pulse generator and 1 or more leads inside the heart, can terminate many ventricular tachycardias (VTs) with either a high-energy discharge (shock) or antitachycardia pacing (ATP). ATP disrupts a VT circuit by painlessly rapid pacing from a remote site and has proved foundational in treatment of potentially lethal cardiac rhythms. However, ATP can also accelerate what might otherwise be more stable, and potentially even transient, VTs into more rapid and unstable rhythms such as ventricular fibrillation. Seminal trials such as PAINFreeRx II and MADIT-RIT helped define the parameters for effective ATP that lead to improved mortality and marked reduction in ICD shocks. In this issue of JAMA, the APPRAISE ATP randomized clinical trial, evaluating more than 2600 patients across 8 countries, affirms the utility of ATP with respect to time to all-cause ICD shock, the trial’s primary end point, with a hazard ratio of 0.72 (95.9% CI, 0.57-0.92) favoring the application of ATP prior to ICD shock compared with shock only. Similarly, secondary end points, including time to appropriate ICD shocks (for VT or ventricular fibrillation) and inappropriate shocks (those precipitated by any other rhythm) favored the ATP plus shock group. These data solidify ATP before shock as standard of care and suggest strong consideration for an ATP-first ICD programming strategy.