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.