Influence of cycle length variations on antitachycardia pacing effectiveness among ICD patients

Background Antitachycardia pacing (ATP) fails to terminate 5% to 25% of ventricular tachycardias (VTs) occurring in implantable cardioverter-defibrillator patients. We speculated that small fluctuations in VT cycle length (CL) may be related to the efficacy of subsequent ATP. Objective The purpose of this study was to determine the relationship between the R-R variations of the last 12 R-R intervals before ATP and the efficacy of the first ATP attempt. Methods We studied 551 VTs (CL 329±35 ms) occurring in 67 patients. We also analyzed the percentage of variation (P-RR), which was calculated by dividing the mean difference between each R-R interval and the next one by the CL (×100), and the acceleration index (AI), which was calculated by dividing the CL of the first 6 R-R intervals by the CL of the next 6. Results The effectiveness of the first ATP therapy was 81%, being higher in VTs with AI