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 o f antitachycardia pacing (ATP) in third-generation implantable cardiov erter defibrillators (ICDs) for terminating spontaneously occurring ve ntricular tachycardias (VTs) in patients with severely depressed left ventricular (LV) function. Ninety-one patients with active ATP were fo llowed for 16 +/- 13 months. During this period, 775 VT episodes occur ring in 36 patients were treated by ATP. The patients were divided int o two groups according to their LV ejection fraction (LVEF): group A w ith LVEF less than or equal to 30% (n = 20), and group B with LVEF > 3 0% (n = 16). There were no differences between both groups in age, gen der, underlying heart disease, indication for ICD therapy, or drug the rapy. The VT rates were comparable (group A: 183 +/- 16 beats/min; gro up B: 180 +/- 21 beats/min; P = NS). Eighty-three percent of all episo des (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 accelera ted by ATP into the ventricular fibrillation zone versus 2% in group B (P < 0.01). The individual termination rare 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 th erapy 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 u nsuccessful ATP was comparable in both groups (group A: 65%; group B: 56%; P = NS). We conclude that ATP is effective and safe in patients w ith recurrent VTs and severely depressed LV function, and it can be sa fely programmed in this group of patients to minimize the use of shock therapy.