Evaluation of defibrillation safety and shock reduction in implantable cardioverter-defibrillator patients with increased time to detection: A randomized SANKS study.

BACKGROUND: The need for ways to minimize the number of implantable cardioverter-defibrillator (ICD) shocks is increasing owing to the risk of its adverse effects on life expectancy. Studies have shown that a longer detection time for ventricular tachyarrhythmia reduces the safety of therapies, in terms of syncope and mortality, but not substantially in terms of the success rate. We aimed to evaluate the effects of increased number of intervals to detect (NID) VF on the safety of ICD shock therapy and on the reduction of inappropriate shocks. METHODS: The present study was a prospective, multicenter, randomized, crossover study. Randomized VF induction testing with NID 18/24 or 30/40 was performed to compare the success rate of defibrillation with a 25-J shock and the time to detection. Inappropriate shock episodes were simulated retrospectively to evaluate a possibility of episodes avoidable at NID 24/32 and 30/40. RESULTS: Thirty-one consecutive patients implanted with an ICD or cardiac resynchronization therapy-defibrillator (CRT-D) were enrolled in this study. The success rate of defibrillation was 100% in both NID groups at the first shock. The time from VF induction to detection showed a significant increase in the NID 30/40 group (6.16±1.29 s vs. 9.00±1.31 s, p<0.001). Among the 120 patients implanted with an ICD or CRT-D, 10 experienced 32 inappropriate shock episodes. The inappropriate shock reduction rate was 53.1% and 62.5% with NID 24/32 and 30/40, respectively. CONCLUSIONS: The findings of this SANKS study suggest that VF NID 30/40 does not compromise the safety of ICD shock therapy, while decreasing the number of inappropriate shocks.

Clinical efficacy of cardiac resynchronization therapy with an implantable defibrillator in a Japanese population: results of the MIRACLE-ICD outcome measured in Japanese indication (MOMIJI) study.

BACKGROUND: Cardiac resynchronization therapy (CRT) is effective in reducing morbidity and mortality in systolic heart failure patients with cardiac dyssynchrony as demonstrated in studies with primarily Western populations. Although CRT devices with a defibrillator (CRT-D) became available in Japan since 2006, their efficacy remains uncertain in Japanese patients. In this prospective, multicenter study, the efficacy of CRT-D therapy in an all-Japanese population was compared with the study conducted in the US, Multicenter InSync ICD Randomized Clinical Evaluation (MIRACLE-ICD). METHODS AND RESULTS: Ninety-three patients were evaluated according to the subject selection criteria of the MIRACLE-ICD study, and 80 patients were enrolled. Results at baseline and 6-month post-CRT-D implantation were compared in terms of composite clinical response (CCR) and other secondary endpoints. Quality of life (QOL) was assessed with a validated Japanese version of the Minnesota Living with Heart Failure questionnaire. CCR was improved in 55 patients (68.8%), unchanged in 14 (17.5%), and worsened in 11 patients (13.7%) (MIRACLE-ICD general phase: 62.0%, 13.4% and 24.6%, respectively). Non-inferiority was verified by 1-sided test with 10% equivalence margin. QOL score improved significantly (50.0±26.2 vs. 23.6±20.2, P<0.01). CONCLUSIONS: The MOMIJI study demonstrated that CRT-D effectiveness as assessed with CCR was non-inferior to the trials conducted outside Japan, thus suggesting that the benefits of CRT-D are similar between Japanese and non-Japanese patients.

Significant increase in the incidence of ventricular arrhythmic events after an intrathoracic impedance change measured with a cardiac resynchronization therapy defibrillator.

BACKGROUND: Cardiac resynchronization therapy defibrillator (CRT-D) devices are now capable of monitoring changes in intrathoracic impedance. Intrathoracic impedance monitoring resulting in a fluid index threshold crossing has been proven to predict heart failure (HF) exacerbations. We retrospectively investigated the relationship between changes in intrathoracic impedance and the occurrence of arrhythmic events. METHODS AND RESULTS: From 282 patients with New York Heart Association class III or IV HF who were implanted with a CRT-D device with a fluid index feature based on intrathoracic impedance monitoring capabilities, arrhythmic events were retrospectively analyzed in terms of the threshold crossings. The patients were divided into 2 groups: those with fluid index threshold crossings and those without threshold crossings. A total of 4,725 tachyarrhythmic events were reported in 129 patients (46%), and there were 221 fluid index crossing events in 145 patients (51%) during 10.0 ± 3.2 months. Tachyarrhythmic events were more frequently recorded in patients with threshold crossing events than in those who did not experience a threshold crossing (3,241 vs. 1,484 events, P<0.0001). Ventricular tachyarrhythmic events mainly occurred within the first 30 days after the threshold crossing event; however, a similar trend was not observed for the atrial tachyarrhythmic events. CONCLUSIONS: Intrathoracic impedance monitoring may predict arrhythmic events, especially ventricular arrhythmias, in patients with HF and provides an additional management tool.