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 ar rhythmias. The incorporation of antitachycardia pacing into ICDs has provid ed a better tolerated alternative to shocks but has the potential disadvant age 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 wh o received ICDs, 11 clinical and tachycardia characteristics in the 162 who received antitachycardia pacing therapy for sustained ventricular arrhythm ias were evaluated. Tachycardia episodes were grouped according to outcome of pacing (successful, unsuccessful, acceleration). Of 1,946 episodes, 1,50 2 (77.2%) were successfully reverted with pacing, 322 (16.5%) were unsucces sful, and 121 (6.2%) were accelerated. Antitachycardia pacing was less succ essful in women, patients with a history of myocardial infarction, those wi th more severe left ventricular dysfunction, those who received antiarrhyth mic drugs, and those programmed to ramp pacing. Tachycardia acceleration wa s inversely related to tachycardia cycle length and was more frequent in pa tients programmed to more aggressive ramp pacing protocols. Women had an al most threefold incidence of tachycardia acceleration compared with men (14% vs 5%, P < 0.001). Antitachycardia pacing is generally successful in termi nating ventricular tachycardia and has a low incidence of tachycardia accel eration. Caution should be used with rapid tachycardias and aggressive ramp pacing protocols because of an increased risk of acceleration. Antitachyca rdia pacing appears less successful and has a higher incidence of complicat ions in women.