Objectives: This study compared the efficacy and safety of two antitachycardia pacing algorithms in the treatment of ventricular tachycardia.
Background: There is agreement that antitachycardia pacing should be adapted to tachycardia rate and be delivered in a burst, but the ideal pacing pattern is not well understood. Effective antitachycardia pacing burst patterns include those with a between-burst decrement (SCAN) with or without an additional within-burst decrement (RAMP).
Methods: Prospective randomized crossover comparison of two antitachycardia pacing algorithms (RAMP vs. SCAN) on identical induced sustained ventricular tachycardias was performed.
Results: Sixty-five ventricular tachycardias (mean cycle length 364 +/- 74 ms) from 37 invasive studies performed in 29 patients were studied; 86% of patients had coronary artery disease and 72% were receiving antiarrhythmic therapy at the time of study. Of the 65 tachycardias, 40 were identical pairs and 25 were unpaired (including 8 with a > 30-ms difference in cycle length of induced ventricular tachycardia pairs). In the paired pacing trials, conversion to sinus rhythm occurred, respectively, in 85% of SCAN versus 90% of RAMP protocols (p = 0.63, power = 93%) and within 1.4 +/- 0.7 versus 1.7 +/- 1.1 attempts (p = 0.41). Discordance for pacing success was seen in three pairs. In unpaired trials, conversion to sinus rhythm occurred in 73% and 57%, respectively (p = 0.68, power = 88%). Tachycardia acceleration during pacing occurred in 7 (11%) of 65 attempts (5 SCAN, 2 RAMP). Acceleration in unpaired ventricular tachycardia trials was correlated with tachycardia cycle length. Failure to convert ventricular tachycardia was associated with a shorter tachycardia cycle length (p < 0.05).
Conclusions: In the patients studied, adaptive antitachycardia pacing was safe and effective and, when successful, occurred within three attempts of an 8-beat adaptive burst algorithm. Changes in burst pattern did not affect pacing safety or efficacy. Antitachycardia pacing success was dependent on induced ventricular tachycardia cycle length.