Predictors of appropriate ICD therapy in Japanese patients with structural heart diseases: A major role of prior sustained ventricular tachycardia in secondary prevention

Background: Implantable cardioverter defibrillator (ICD) and cardiac resynchronization with a defibrillator (CRT-D) are established therapies for secondary prevention of sudden cardiac death (SCD) in patients with structural heart disease (SHD), but the rates of subsequent ICD/CRT-D therapy widely differ among patients with SHD. The aim of this study was to determine clinical factors associated with appropriate therapy for preventing SCD in patients with SHD.

Methods: We enrolled 147 patients with SHD (mean age, 59 ± 15 years; mean ejection fraction [EF], 45 ± 15%) who underwent ICD/CRT-D implantation for secondary prevention of SCD (ischemic heart disease, n = 50; nonischemic heart disease, n = 97). ICD/CRT-D was implanted for aborted cardiopulmonary arrest (CPA, n = 65) or sustained ventricular tachycardia (VT, n = 82).

Results: During a follow-up period of 3.2 ± 3.6 years, 79 of the 147 patients had appropriate ICD/CRT-D therapies. A Kaplan-Meier survival curve showed that the rate of appropriate therapy was 54% at 5-year follow-up. Prior sustained VT, lower EF, and use of a class I antiarrhythmic drug were significantly more frequent in patients with appropriate therapy. In multivariate analysis, prior sustained VT (hazard ratio, 2.8; 95% CI, 1.60-4.46; P = .001) was the only independent predictor for appropriate ICD/CRT-D therapy. Kaplan-Meier survival curves showed that rates of appropriate therapy during a 5-year follow-up period were 70% and 34% in patients with sustained VT and those with CPA, respectively (P = .001).

Conclusions: In SHD patients implanted with an ICD/CRT-D, prior sustained VT as an indication of ICD/CRT-D implantation, but not EF or an antiarrhythmic drug, predicts a high rate of appropriate therapy.