V. COMPLICATIONS
A. Acute Myocardial Infarction
Although intraoperative myocardial protection with improvements in surgical techniques has advanced during the past decade, perioperative myocardial infarction (listed in Table 1) occurs in 7–12% of patients. Causes of peri-operative myocardial infarction include incomplete revas-cularization, thrombosis of the native coronary artery, diffuse atheromatous formation of the coronary artery distal to the bypass graft, technical problems with the surgical anastomosis, inadequate myocardial preservation intraoperatively, increased myocardial oxygen needs during surgery, hypotension caused by bleeding or medications, and tachycardia and abnormal heart rhythms such as atrial fibrillation that increase myocardial oxygen demand.
The diagnosis of perioperative myocardial infarction is difficult because there is virtually always elevation of myocardial creatine kinase (CK–MB) following surgery; nonspecific ECG changes occur postoperatively and these important diagnostic tests of acute myocardial infarc¬tion become nondiagnostic. The ECG still remains the most useful test, however, for diagnosis of perioperative infarction. The presence of new Q waves accompanied by evolutionary ST or T-wave changes should suggest infarction.