Physiologic improvement following coronary artery bypass surgery.

Abstract

SUMMARY In this study the effects of coronary artery bypass surgery on ventricular function were evaluated at rest by quantitative analysis of segmental wall motion on cineventriculography, and during maximal treadmill exercise by measurement of serial cardiac outputs (Fick method) with the use of indwelling pulmonary artery and radial artery catheters. The patient had single vessel coronary disease and exertional angina. Following placement of a bypass graft to the proximally occluded left anterior descending coronary artery, and despite the presence of arterial hypoxemia secondary to interstitial IN ADDITION TO RELIEVING anginal symptoms, coronary artery bypass surgery can improve left ventricular function by augmenting myocardial blood flow. Although resting ventricular function does not often improve after bypass surgery,13 an increased maximal heart rate, ratepressure-product, and exercise duration on multistage treadmill testing are characteristically observed postoperatively.4`6 In such patients, cardiac output and oxygen uptake increase significantly at maximal exercise postoperatively (P < 0.01), but a reduction in stroke volume has been observed after surgery.7 To further evaluate the effects of bypass surgery, circa 1976, on left ventricular function we have applied computer techniques to quantitatively evaluate segmental wall motion on cineventriculograms at rest and have measured serial cardiac output by means of indwelling radial artery and pulmonary artery catheters during symptom-limited maximal treadmill exercise.The patient reported here underwent hemodynamic studies during exercise before and after aortocoronary bypass surgery of one artery. Despite the presence of chronic pulmonary dysfunction, a striking increase in maximal cardiac output occurred after surgery, mediated by a rise in both maximal heart rate and stroke volume. By conventional criteria resting ventricular function was normal before and after surgery, but preoperative abnormalities in segmental wall motion, identified quantitatively, were restored to normal following bypass surgery. Methods Angiographic EvaluationSingle plane cineventriculograms were done before and six months after surgery. Left ventricular chamber volumes were computed using the area-length method.8 Focal abnormalities of time and extent of contraction were evaluated by computer-assisted frame-by-frame analysis of the cineventriculograms which were taken at 60 frames per second.9 10The left ventricle was divided into 20 segments and the ex- pulmonary fibrosis, a striking increase in maximal cardiac output occurred, mediated by a rise in both maximal heart rate and stroke volume. In this patient, resting ventricular volumes and ejection fraction were normal both before and after surgery, but preoperative abnormalities in extent of segmental wall motion, identified quantitatively, were restored to normal after bypass grafting. These investigations indicate that bypass surgery can provide substantial physiologic benefits in addition to providing subjective relie...