Background: Current discrimination algorithms do not completely avoid inappropriate tachycardia detection.
Objectives: This study analyzes the discrimination capability of the changes of the first postpacing interval (FPPI) after successive bursts of anti-tachycardia pacing (ATP) trains in implantable cardioverter-defibrillator (ICD)-recorded tachycardias.
Methods: We included 50 ICD patients in this prospective study. We hypothesized that the FPPI variability (FPPIV) when comparing bursts with different numbers of beats would be shorter in ventricular tachycardias (VTs) compared with supraventricular tachycardias (SVTs). The ATP (5-10 pulses, 91% of tachycardia cycle length) was programmed for tachycardias >240 ms.
Results: Anti-tachycardia pacing was delivered during 37 sinus tachycardias (STs) in an exercise test, 96 induced VTs in an electrophysiological study, and 198 spontaneous episodes (144 VTs and 54 SVTs). The FPPI remained stable after all ATP bursts in VT but changed continuously in SVT; when comparing bursts of 5 and 10 pulses, the FPPIV was shorter in VT (34 +/- 65 vs.138 +/- 69, P<.0001, in all T and 12 +/- 20 vs. 138 +/- 69, P<.0001, in T>or=320 ms) than in SVT. In T>or=320 ms an FPPIV<or=50 ms between bursts of 5 and 10 pulses classified correctly 100% of VTs and 90% of SVTs. Anti-tachycardia pacing terminated 66% of induced VTs, 60% of spontaneous VTs, and 20% of spontaneous SVTs and induced no VT during spontaneous or exercise induced SVT. Five induced and two spontaneous VT episodes were accelerated.
Conclusions: Analysis of FPPIV after ATP discriminates ICD-detected T. Successive bursts (of ATP) trains at 91% of tachycardia cycle length are safe, despite being delivered before rhythm classification.