Basal Exit Site of Clinical Ventricular Tachycardia is an Independent Predictor of Antitachycardia Pacing Failure in Implantable Cardioverter‐Defibrillators Recipients

BACKGROUND: Little is known about predictors of antitachycardia pacing (ATP) failure in implantable cardioverter defibrillator (ICD) recipients. Distance between the stimulation site and the ventricular tachycardia (VT) site of origin may critically affect ATP effectiveness. We hypothesized that ATP may be less effective in ICD patients who had basal VT than in those who had apical VT. METHODS: We reviewed data from 52 patients with sustained monomorphic VT and left ventricular disease referred for ICD implantation. ATP was delivered exclusively at the right ventricular apex. The clinical VTs site of origin (basal, midventricular, or apical) was determined in each patient, using 12-lead electrocardiogram. VTs episodes treated with ATP during the 1-year follow-up were studied. ATP success rate (%), defined as the ratio between the number of successful ATP sequences and the number of delivered ATP sequences, was determined in each patient. RESULTS: VT exit site was apical in 19 patients (36%), basal in 18 patients (35%), and midventricular in 15 patients (29%). In those 52 patients, 1,393 ATP sequences, delivered to treat 761 VT episodes, were analyzed. ATP success rate was found to be associated with the VT site of origin (median [interquartile range]): basal (33%[11-67]), midventricular (50%[37-100]), apical (100%[41-100]) (P = 0.027). Multivariate analysis identified basal VT site of origin as an independent predictor of ATP failure (P = 0.023). CONCLUSION: ATP is less effective in ICD patients who had basal VT than in those who had apical VT before ICD implantation.