Significance of clinical ventricular tachycardias induced by antitachycardia pacing in patients with prior myocardial infarction

Abstract

In patients with implantable cardioverter-defibrillator (ICD), ventricular tachycardia (VT) can occur spontaneously or as a result of antitachycardia pacing (ATP) that changes, rather than terminates, a spontaneous VT to a different VT. The relevance of ATP-induced VTs is uncertain. The purpose of this study was to assess the clinical relevance of ATP-mediated VTs in patients undergoing VT ablation procedures. Stored ICD electrograms of 162 consecutive patients with prior myocardial infarction referred for VT ablation (mean age 67.5 ± 9.2 years; 150 men; median ejection fraction 25% [IQR 20%-35%]) were reviewed. Clinical VTs were classified as spontaneous or ATP-induced. All VTs were targeted during the ablation procedures. Of 554 ICD-recorded clinical VTs, 157 (28%) were ATP-induced (63 patients) and 397 (72%) were spontaneous. ATP-induced VTs were faster (cycle length 316 ± 62 ms vs 369 ± 83 ms; P < .001), less commonly inducible with invasive programmed stimulation (35% vs 52%; P < .001), and less commonly had identifiable target sites (21% vs 40%; P<.001) than were spontaneous VTs. During a median follow-up of 368 days [IQR: 68-1106] postablation, 71 VTs recurred (39 patients), none of which was a previously documented ATP-induced VT. A history of ATP-induced VT was associated with an increase in VT recurrence. ATP-induced VTs occur frequently in patients with prior myocardial infarction presenting for VT ablation procedures. The presence of ATP-induced VT is associated with a higher VT recurrence rate postablation. None of the ATP-induced VTs recorded before the ablation procedure recurred postablation, and therefore ATP-induced VTs represent a marker rather than the cause of VT recurrence.