Clinical predictors and efficacy of antitachycardia pacing in patients with implantable cardioverter defibrillators: the importance of the patient's sex.

The ICD has become accepted as primary therapy for malignant ventricular arrhythmias. The incorporation of antitachycardia pacing into ICDs has provided a better tolerated alternative to shocks but has the potential disadvantage of delaying definitive therapy. Accordingly, we sought to delineate the characteristics of patients likely to experience unsuccessful termination of pacing and to identify ineffective pacing strategies. Of 519 patients who received ICDs, 11 clinical and tachycardia characteristics in the 162 who received antitachycardia pacing therapy for sustained ventricular arrhythmias were evaluated. Tachycardia episodes were grouped according to outcome of pacing (successful, unsuccessful, acceleration). Of 1,946 episodes, 1,502 (77.2%) were successfully reverted with pacing, 322 (16.5%) were unsuccessful, and 121 (6.2%) were accelerated. Antitachycardia pacing was less successful in women, patients with a history of myocardial infarction, those with more severe left ventricular dysfunction, those who received antiarrhythmic drugs, and those programmed to ramp pacing. Tachycardia acceleration was inversely related to tachycardia cycle length and was more frequent in patients programmed to more aggressive ramp pacing protocols. Women had an almost threefold incidence of tachycardia acceleration compared with men (14% vs 5%, P < 0.001). Antitachycardia pacing is generally successful in terminating ventricular tachycardia and has a low incidence of tachycardia acceleration. Caution should be used with rapid tachycardias and aggressive ramp pacing protocols because of an increased risk of acceleration. Antitachycardia pacing appears less successful and has a higher incidence of complications in women.