Recordings from the slow zone of reentry during burst pacing versus programmed premature stimulation for initiation of reentrant ventricular tachycardia in patients with coronary artery disease.

Programmed premature stimulation and burst pacing were compared for initiation of ventricular tachycardia (VT) in 16 patients with inducible sustained monomorphic VT. In all patients VT could be induced by programmed stimulation with 2 or 3 extrastimuli. On the other hand, initiation of VT by burst pacing was dependent on the length of the train; only 2 to 4 of the 11 trains tested could induce VT in any single patient. Recordings obtained from the slow zone of reentry showed that programmed premature stimulation that induced VT resulted in a critical degree of conduction delay as revealed by lengthening of local fractionated electrograms spanning 70 to 100% of the diastolic interval. Similarly, the last beat of a burst pacing train that induced VT was always followed by a similar degree of local conduction delay, whereas trains that failed to induce VT were followed by a lesser delay. It is concluded that although programmed stimulation with up to 3 extrastimuli was consistently successful in inducing VT, burst pacing succeeded in only 26% of the trials and was dependent on the length of the train, which varied from one patient to the other. Similar to what was shown previously in the experimental model of reentrant VT, burst pacing could initiate, conceal, terminate, and reinitiate reentry depending on the length of the train.