Postextrasystolic potentiation: Analysis of methods of induction

Studies were conducted in 15 patients with coronary artery disease to determine (1) if the type of pacing used to induce an extrasystole had a bearing on subsequent postextrasystolic potentiation (PESP) and (2) if the fact that these were evaluated in jeopardized or nonjeopardized portions of the ventricle altered the ability to assess PESP. Two types of pacing were used. In the first group, all beats in the test sequence (basic heart rate, extrasystole, and postextrasystole) were delivered from a programmed external pacemaker. This group was termed the “all-paced” (AP) group, and the postextrasystole was introduced before a compensatory pause could occur, so that loading conditions within the ventricle at the last regular beat and after the extrasystole were not different. In the second group, the extrasystole was coupled to the sensed intrinsic heart rate of the patient, and the postextrasystole was allowed to occur spontaneously. This group was termed the “sensed-paced” (SP) group. Despite differences in basic heart rates and postextrasystolic intervals between the two groups, comparable results were obtained with the two techniques. However, the postextrasystole in the SP group occurred much earlier than expected, probably due to intrinsic cardioacceleration during ventriculography. The net result was that loading conditions in this group before and after the extrasystole were also not different from each other. Results from the pacing techniques were not influenced by whether they were obtained from jeopardized or nonjeopardized segments. It is suggested that PESP is a useful tool in the quanitative assessment of latent ventricular function in patients with coronary artery disease, but only if the pacing technique assures identical ventricular loading at the last regular beat and after the extrasystole.