Abstract 17176: Prognostic Importance of Defibrillator Appropriate Shocks and Anti Tachycardia Pacing in Mild Heart Failure Patients

Abstract

Background: Previous studies had shown that patients with heart failure (HF) who receive implantable cardioverter-defibrillator (ICD) for primary prevention are at increased risk for mortality if they receive a shock. However, information about the prognostic importance of therapies [both shock and anti-tachycardia pacing (ATP)] delivered for a different ventricular arrhythmia (VA) rate is limited. Methods: We evaluated the risk for death among 1790 ICD implanted patients from the Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy using a time dependent analysis. Patients were categorized to mutually exclusive groups by either the rate of the treated VA (categorized at 200 bpm) or the type of the therapy and VA rate (ATP or shock both categorized at 200 bpm), the reference group was patients that had no device therapy. Results: During a median follow-up time of 4 years 423 patients had appropriate ICD therapy, with 163 receiving therapy for VA< 200 bpm only, and 260 for VA≥200 bpm. ICD therapy for VA≥200 was associated with significant increased mortality (HR=2.27 CI 1.48-3.48, p<.001), while therapy for VA<200 was not different from the no therapy group (HR=1.45 CI=0.86-2.44, p=0.162). Accordingly, in a second model both shocks and ATPs for VA≥200 were associated with increased mortality (HR=2.96 CI 1.91-4.60 p<.001 and HR=2.22 CI 0.96-5.14, p=0.063 respectively), while shocks and ATPs for VA<200 did not differ from the no therapy group (HR=1.43 CI 0.52-3.92 p=0.489 and HR=1.43 CI 0.80-2.56, p=0.232 respectively). Conclusions: In mild HF patients, who receive ICD for primary prevention, mortality is associated with the rate of the arrhythmia rather than the device rendered therapy.