Implantable cardioverter defibrillators improve survival of patients at risk for ventricular arrhythmias, but inappropriate shocks occur in up to 30% of patients and have been associated with worse quality of life and prognosis. In heart failure patients with cardiac resynchronization therapy defibrillators (CRT-Ds), we evaluated whether a new generation of detection and discrimination algorithms reduces inappropriate shocks.Methods and results
We analysed 1983 Medtronic CRT-D patients (80% male, 67 ± 10 years), 1368 with standard devices (Control CRT-D) and 615 with new generation devices (New CRT-D). Expert electrophysiologists reviewed and classified the electrograms of all device-detected ventricular tachycardia/fibrillation episodes. Total follow-up was 3751 patients-years. Incidence of inappropriate shocks at 1 year was 2.8% [95% confidence interval (CI) = 2.0–3.5] in Control CRT-D and 0.9% (CI = 0.4–2.2) in New CRT-D (hazard ratio = 0.37, CI = 0.21–0.66, P < 0.001). In New CRT-D, inappropriate shocks were reduced by 77% [incidence rate ratio (IRR) = 0.23, CI = 0.16–0.35, P < 0.001] and inappropriate anti-tachycardia pacing by 81% (IRR = 0.19, CI = 0.11–0.335, P < 0.001). Annual rate per 100 patient-years for appropriate VF detections was 3.0 (CI = 2.1–4.2) in New CRT-D and 3.2 (CI = 2.1–5.0) in Control CRT-D (P = 0.68), for syncope was 0.4 (CI = 0.2–0.9) in New CRT-D and 0.7 (CI = 0.5–1.0) in Control CRT-D (P = 0.266), and for death was 1.0 (CI = 0.6–1.6) in New CRT-D and 3.5 (CI = 3.0–4.1) in Control CRT-D (P < 0.001).Conclusion
Detection and discrimination algorithms used in new generation CRT-D significantly reduced inappropriate shocks when compared with standard CRT-D. This result, with no compromise on VF sensitivity or risk of syncope, has important implications for patients' quality of life and prognosis.