ANTITACHYCARDIA PACING IN PATIENTS WITH IMPLANTABLE CARDIOVERTER-DEFIBRILLATORS - HOW MANY ATTEMPTS ARE USEFUL

The purpose of this study was to determine the termination and acceler ation rates for 1 to 6 attempts of antitachycardia pacing (ATP) delive red by ICD in order to terminate spontaneously occurring VTs. Twenty-f our ICD recipients with active ATP programs, including a maximum of si x ATP sequences and spontaneously occurring VTs during follow-up, were investigated. During a mean follow-up of 42+/-15 months (range, 17-63 months) 413 spontaneous VT episodes (17+/-14; range , 1-49 per patien t) resulting in appropriate ATP delivery by the ICD occurred. ATP succ essfully terminated 328 episodes (80%) with a mean number of 1.6+/-1.1 pacing sequences. Eighty episodes (19%) were accelerated by ATP and 5 (1%) were unresponsive to ATP. The ATP success decreased until the th ird ATP sequence (59%-->31%-->24%), but increased again in the fourth to sixth attempt (46%-->46%-->.29%). The acceleration rate increased f rom sequence one to sequence three (8%-->13%-->28%), but decreased sig nificantly in further ATP attempts (19%-->0%-->0%). The mean time dela ys until redetection or termination after 4, 5, and 6 attempts of ATP were 22+/-5 seconds, 37+/-2 seconds, and 41+/-9 seconds, respectively. Nine patients (37%) used greater than or equal to 3 ATP attempts duri ng follow-up and all of them had a therapeutic benefit from it. Five o ut of 13 VTs (38%) treated with greater than or equal to 4 attempts co uld ultimately be terminated by ATP. The results of this study demonst rate that the first ATP sequence is the most effective and that >4 ATP attempts may be useful in a minority of patients. There seems to be a low risk of VT acceleration by the fourth to sixth ATP sequence. Beca use of the associated time delay, a high number of ATP attempts should only be programmed in patients with hemodynamically well-tolerated st able VTs.