Response of the left ventricle in coronary artery disease to postextrasystolic potentiation.
Left ventricular volumes and contractile patterns were evaluated during the first sinus beat after a compensatory pause resulting from ventricular arrhythmia and were compared to the second sinus beat (control beat) in order to evaluate the effect of postextrasystolic potentiation. Twelve patients had no evidence of heart disease (group I). Fifty patients had coronary artery disease and included 14 patients (group IIa) with no prior myocardial infarction and a normal left ventricular contractile pattern and 19 pateints (group IIb) with an abnormal contractile pattern. Seventeen pateints (group IIc) had a documented transmural myocardial infarction as well as an abnormal left ventricular contractile pattern. In all patients the first postextrasystolic sinus beat, when compared to the second sinus beat, demonstrated increases in stroke volume and ejection fraction and decrease in end-systolic volume. There were no qualitative changes in the contractile pattern in the immediate postextrasystolic beat in the patients with normal left ventricular function. In both group IIb and group IIc the changes in end-systolic volume, stroke volume and ejection fraction were significantly greater than observed in groups I and IIa. Abnormal wall segments present in the control beat in groups IIb and IIc demonstrated after postextrasystolic potentiation a normal contractile pattern, improved pattern or no change when compared to the control beat. Abnormal wall segments were more likely to revert to normal as a result of postextrasystolic potentiation in group IIb than group IIc. Akinesia was less likely to revert completely to normal than hyposinesia. In 20 of 24 patients the changes in contractile pattern after aortocoronary bypass surgery corresponded to those observed as a result of postextrasystolic potentiation.