Shocks as predictors of survival in patients with implantable cardioverter-defibrillators.

OBJECTIVES: The objective of the study was to determine whether the occurrence of shocks for ventricular tachyarrhythmias during therapy with implantable cardioverter-defibrillators (ICD) is predictive of shortened survival. BACKGROUND: Ventricular tachyarrhythmias eliciting shocks are often associated with depressed ventricular function, making assessment of shocks as an independent risk factor difficult. METHODS: Consecutive patients (n = 421) with a mean follow-up of 756+/-523 days were classified into those who had received no shock (n = 262) or either one of two shock types, defined as single (n = 111) or multiple shocks (n = 48) per arrhythmia episode. Endpoints were all-cause and cardiac deaths. A survival analysis using a stepwise proportional hazards model evaluated the influence of two primary variables, shock type and left ventricular ejection fraction (LVEF <35% or >35%). Covariates analyzed were age, gender, NYHA Class, coronary artery disease, myocardial infarction, coronary revascularization, defibrillation threshold and tachyarrhythmia inducibility. RESULTS: The most complete model retained LVEF (p = 0.005) and age (p = 0.023) for the comparison of any shock versus no shock (p = 0.031). The occurrence of any versus no shock, or of multiple versus single shocks significantly decreased survival at four years, and these differences persisted after adjustment for LVEF. In the LVEF subgroups <35% and <25%, occurrence of multiple versus no shock more than doubled the risk of death. Compared with the most favorable group LVEF > or =35% and no shock, risk in the group multiple shocks and LVEF <35% was increased 16-fold. CONCLUSIONS: In defibrillator recipients, shocks act as potent predictors of survival independent of several other risk factors, particularly ejection fraction.

Conscious sedation with combined hypnotic agents for implantation of implantable cardioverter-defibrillators.

OBJECTIVES: The objective of this study was to evaluate the feasibility, safety and efficacy of placing implantable cardioverter-defibrillators (ICDs) in the electrophysiology laboratory using conscious sedation with combined hypnotic agents and deep sedation with etomidate. BACKGROUND: Implantable cardioverter-defibrillators with transvenous leads permit the use of simplified implantation techniques similar to those used for the insertion of permanent pacemakers. However, implantation of ICDs without general anesthesia has thus far gained limited acceptance. METHODS: In 162 patients, conscious sedation during ICD placement was achieved with combined intravenous midazolam, morphine and promethazine (Phenergan). Intravenous etomidate was administered to induce deep sedation for defibrillation threshold testing. First-time implantations were in the prepectoral position (n = 142), but some patients with preexisting devices received abdominal implants (n = 20). The results were compared with those of concurrent patients (n = 56) who received prepectoral implants under propofol anesthesia administered by an attending anesthesiologist. RESULTS: The anesthetic protocol was implemented without major intraoperative complications. During deep sedation with etomidate, episodes of apnea, hypoxia or arterial hypotension requiring therapeutic intervention did not occur. During a mean (+/-SD) follow-up period of 257 +/- 140 days (median 227, range 14 to 482), there were, among the 162 patients, a total of two nonsudden cardiac deaths-one 71 days and the other 157 days after the operation. There were two nonsudden deaths in the concurrent control subjects (n = 56)-one 13 days and the other 110 days after the operation. CONCLUSIONS: Implantation of ICDs under conscious sedation with combined hypnotic agents and deep sedation with etomidate is a safe and effective procedure with low perioperative morbidity and low long-term complication rates.

Effect of preexisting epicardial patch electrodes on defibrillation thresholds of unipolar defibrillators.

The question is addressed whether patients with thoracotomy defibrillators and failing epicardial electrodes can be effectively treated with the implantation of prepectoral unipolar ("active can") defibrillators. Results indicate that abandoned epicardial patches in the pathway of unipolar defibrillation currents do not affect defibrillation thresholds and active can efficacy.