Safety of antitachycardia pacing in patients with implantable cardioverter defibrillators and severely depressed left ventricular function.

The purpose of this study was to investigate the efficacy and safety of antitachycardia pacing (ATP) in third-generation implantable cardioverter defibrillators (ICDs) for terminating spontaneously occurring ventricular tachycardias (VTs) in patients with severely depressed left ventricular (LV) function. Ninety-one patients with active ATP were followed for 16 +/- 13 months. During this period, 775 VT episodes occurring in 36 patients were treated by ATP. The patients were divided into two groups according to their LV ejection fraction (LVEF): group A with LVEF < or = 30% (n = 20), and group B with LVEF > 30% (n = 16). There were no differences between both groups in age, gender, underlying heart disease, indication for ICD therapy, or drug therapy. The VT rates were comparable (group A: 183 +/- 16 beats/min; group B: 180 +/- 21 beats/min; P = NS). Eighty-three percent of all episodes (n = 332) in group A and 93% of the VTs (n = 443) in group B were ATP terminated (P < 0.01). Ten percent of VTs in group A were accelerated by ATP into the ventricular fibrillation zone versus 2% in group B (P < 0.01). The individual termination rate and acceleration rate per patient were comparable in both groups. All VT episodes unresponsive to ATP were converted by backup shocks. The efficacy of first-shock therapy was similar in both groups (group A: 89%; group B: 97%; P = NS). The proportion of patients who needed at least one backup shock for unsuccessful ATP was comparable in both groups (group A: 65%; group B: 56%; P = NS).(ABSTRACT TRUNCATED AT 250 WORDS)