Randomized controlled comparison of antitachycardia pacing algorithms for termination of ventricular tachycardia

Division of Cardiology, St. Michael's Hospital, Toronto, Ontario, Canada.

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.

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