"Isolength" postextrasystolic potentiation as a predictor of functional restoration following surgical revascularization for myocardial ischemia.

A previously developed method of programmed postextrasystolic potentiation (PESP) was assessed in eight patients with medically refractory unstable angina, as a predictor of functional restoration resulting from surgical revascularization. Prior to coronary arteriography, left ventricular segmental wall motion was determined during ventricular pacing and the first postextrasystolic beat following an extrasystole. The postextrasystole was induced at an interval calculated to occur at a time where ventricular preload was identical to the regular paced beat (isolength interval). The left ventricular wall was divided into six segments, each subscribing one area of the ventriculogram, and correction for rotation during systole was made. Of 48 segments, 21 were considered "jeopardized," due to greater than 70% reduction in cross-sectional lumen of the serving coronary arteries. Fifteen of these 21 responded to PESP, increasing their segmental area ejection fraction from 44 +/- 5 (paced "normal" beat) to 56 +/- 6 (postextrasystolic beat) (p less than 0.05). Following surgical revascularization, these segments showed an improvement in their baseline area ejection fraction from 44 +/- 6 to 58 +/- 5 (p less than 0.05). Six jeopardized segments that failed to respond to PESP prior to revascularization showed functional deterioration after revascularization. The 27 non-jeopardized segments (which were not revascularized) also showed functional improvement, suggesting improved collateral flow. This study demonstrates that isolength postextrasystolic potentiation obtained with a standardized pacing protocol may be used to predict the potential for improvement in cardiac function following surgical revascularization. Our results also show that lack of PESP predicts loss of left ventricular myocardial function following revascularization.