A number of modes of antitachycardia pacing
therapies are available in the newer generations of
implantable cardioverter/defibrillators. The efficacy of synchronized burst overdrive pacing for the termination of induced and spontaneous monomorphic
ventricular tachycardia (VT) was compared with synchronized autodecremental (ramp) pacing in 21 patients who received an implantable antitachycardia pacemaker/cardioverter/
defibrillator for treatment of recurrent sustained monomorphic VT. Patients undergoing serial noninvasive VT induction studies after device implantation were prospectively randomized to receive trials of burst or ramp pacing
therapies in a crossover study design. Antitachycardia pacing
therapies were equally efficacious in treating induced VT (68% for ramp, 76% for burst pacing trials). The efficacy of ramp (93%) and burst (96%) pacing
therapies was significantly higher in terminating spontaneously occurring episodes of VT than in terminating induced episodes (p = 0.001). The incidence of
tachycardia acceleration was similar for both modes of pacing. The incidence of VT acceleration was lower for spontaneously occurring episodes of VT (0.01%) than for induced episodes of VT (6%, p < 0.01). Thus, antitachycardia pacing is an effective
therapy for episodes of monomorphic VT, and the risk of accelerating VT to a hemodynamically unstable form is low. Antitachycardia pacing
therapies are more effective against spontaneously occurring episodes than induced episodes of VT. Differences in
tachycardia cycle length and duration may contribute to these effects.