A PROSPECTIVE RANDOMIZED REPEAT-CROSSOVER COMPARISON OF ANTITACHYCARDIA PACING WITH LOW-ENERGY CARDIOVERSION

Background. Multiprogrammable antiarrhythmia devices can treat monomor phic ventricular tachycardia (VT) with autodecremental overdrive pacin g and/or with low-energy cardioversion. These two methods provide the opportunity to decrease patient discomfort typically experienced with high-energy pulses. Although both therapies are known to be effective, controversy persists over their relative safety and efficacy. Methods and Results. The purpose of this study was to examine the safety and efficacy of autodecremental overdrive pacing and low-energy cardiovers ion in reproducibly terminating monomorphic VT in 24 patients with mul tiprogrammable antiarrhythmia devices. The protocol required that iden tical ECG morphology VT be reproducibly induced four times to assess t he outcome of antitachycardia pacing and cardioversion twice for each patient in a randomized fashion. Each episode of VT was induced via th e implanted device. Autodecremental overdrive pacing initially began w ith seven stimuli at 97% of the VT cycle length, decrementing by 10 ms ec per stimulus to a minimum coupling interval of 200 msec. If ineffec tive, autodecremental overdrive pacing was allowed to iterate three mo re times for a total of four pacing interventions. With each iteration , one stimulus was added to the pacing train. Similarly, with low-ener gy cardioversion, up to four therapeutic attempts were made, beginning with a 0.2-J pulse. If ineffective, pulse energy was increased to 0.4 , 1.0, and finally 2.0 J. All interventions were automatic without hum an interference. VT (cycle length, 306 +/- 42 msec) was repeatedly ter minated in 15 of 24 patients (63%) by autodecremental overdrive pacing and in 18 of 24 patients (75%) by low-energy cardioversion (p=0.53). Eight of the 24 patients (33%) had their VT terminated repeatedly by b oth therapies. VT accelerated to faster VT or ventricular fibrillation by autodecremental overdrive pacing in four of 24 patients (17%) and by low-energy cardioversion in five of 24 (21%) (p=0.88). Only one of the 24 patients (4%) accelerated with both therapies. No patient was u naffected by either therapy. Conclusions. In the manner programmed, au todecremental overdrive pacing and low-energy cardioversion have simil ar efficacy and acceleration rates. Response to one therapy does not p redict response to the other.