Sequential studies of left ventricular function and wall motion after coronary arterial bypass surgery

Left ventricular performance and segmental wall motion were studied sequentially in 12 patients during the 1st postoperative year after coronary arterial bypass graft surgery with use of computer-aided fluoroscopic analysis of radiopaque tantalum markers implanted into the left ventricular wall at operation. Measurements were made 1 week, 2 months and 1 year after operation. Ejection fraction decreased significantly early postoperatively (to 42 ± 3 percent [mean ± standard error of the mean]) but recovered to near preoperative values (55 ± 3 percent) at 2 months (49 ± 2 percent) and 1 year (51 ± 3 percent). Stroke volume increased from 51 ± 4 ml 1 week after operation to 70 ± 6 ml at 1 year; heart rate decreased from 91 ± 2 to 69 ± 4 beats/min during this interval. Both circumferential fiber shortening velocity and cardiac output were constant over the year. Total peripheral resistance was reduced in the early postoperative period. The data in the early postoperative period were consistent with those observed with an increase in heart rate alone, with only a small chronotropic augmentation of the myocardial contractile state. Total wall motion increased from 1 week to 2 months after operation primarily because of an increase in the extent of contraction of inferior wall segments, particularly in zones of previous infarction. Five of seven patients who had a preoperative myocardial infarction with hypokinesia of the infarcted region showed increased shortening in the region in the first 2 postoperative months. Four of six patients whose ejection fraction was less than 40 percent 1 week after operation had recurring angina; the six patients with a larger ejection fraction at this time had no recurrence.Because resting left ventricular performance varies significantly during the 1st postoperative year, it is concluded that (1) results of evaluations made at widely differing times after operation should not be pooled in determining operative results; (2) studies made 2 or more months postoperatively are not subject to the rapidly changing values associated with the early postoperative period; (3) frequent sequential studies of left ventricular performance are required to evaluate operative outcome in an individual patient; and (4) wall motion in regions of previous infarction can be improved by coronary bypass graft surgery.