Myocardial Infarction after Aortocoronary Bypass Surgery. The Incidence in 187 Consecutive Patients and the Late Postoperative Significance

Abstract

The incidence of postoperative acute myocardial infarction (AMI) was studied by serial postoperative ECG recordings in 187 patients, who underwent aortocoronary bypass surgery at Ullevål Hospital during the years 1971 to 1975. The occurrence of postoperative AMI was related to serial serum enzyme analyses and to short-and long-term prognoses.

ECG signs of postoperative AMI were found in 10 patients (5.3%) and of possible AMI in 12 patients (6.4%). The location of the infarcts was inferior in 7 of the 10 patients with AMI. Only 1 of the patients died postoperatively. In the others the recovery was uneventful.

S-GOT/ASAT and S-LDH/LD values were significantly higher in patients with ECG changes compatible with postoperative AMI than in patients with uncertain or no ECG findings. Maximal S-GOT/ASAT value more than 100 U/l was found in 8 out of 9 patients with postoperative AMI, in whom serum enzyme levels were measured, and in 6 out of 12 patients with possible AMI. The combination of postoperative ECG signs of AMI or possible AMI and S-GOT/ASAT value of more than 100 U/l was found in 14 of 187 patients (7 4%). The real incidence of postoperative AMI in the present material was therefore assumed to be 7–8%.

One of the patients died postoperatively. At a mean observation time of 40 months, none of the other patients with postoperative AMI had died or suffered a new AMI after discharge from hospital. Subjectively, the result of surgery was very good or good in all patients except one.

Late postoperative haemodynamic studies indicated no deterioration of left ventricular function in patients with postoperative AMI or possible AMI. New areas of impaired left ventricular contractility were found in 5 of 8 patients with AMI and in 2 of 10 patients with possible postoperative AMI who underwent re-examination. An anatomical correspondence was found between the new areas of impaired ventricular function and new segments of stenosis or occlusion in the coronary arteries. Postoperative AMI was not related to occlusion of the aortocoronary bypass grafts.