[Study on risk factors and late results of coronary artery bypass grafting for acute myocardial infarction].

Study was made on the operative results, risk factors, and late results of coronary artery bypass grafting (CABG) for acute myocardial infarction (AMI) conducted at our hospital. The subjects of the present study were 70 cases of AMI who underwent CABG during a period of five years from January 1991 to December 1995. They were composed of 61 males and 9 females whose mean age was 61.9 years. LMT disease was observed in 13 cases and preoperative shock in 18 cases. The mean aortic cross-clamp time was 64 minutes with the mean extracorporeal circulation time being 134 minutes and the mean number of grafts being 2.5. The mean preoperative-postoperative peak creatine kinase was 4479 IU/L. The number of operative deaths was 14 with a mortality rate of 20%. When compared with elective cases of CABG conducted during the same period with a mortality rate of 2.7%, the operative result of AMI was poor. The mortality rate by risk factor was 40% for age of 70 years or more, 46.2% for complication of LMT disease, 52.9% for preoperative shock, 58.3% for preoperative C.I. of less than 2.0, 80% for postoperative C.I. of less than 2.0, 28.2% for conduct of postoperative circulatory support, and 42.1% for peak creatine kinase of 5000 IU/L or more. Aortic cross-clamp time and reperfusion time (interval from onset of AMI to aortic declamp) were found not to be risk factors. Late death accounted for 5 cases including one case of cardiac death due to suspected AMI. Survival rate excluding operative deaths and hospital deaths was 98% in one year and 83.9% in five years. When compared to non cardiacevent cases, the survival rate of positive cardiac event cases was significantly poor. The operative results of severe myocardial ischemia cases represented by cases of complication of LMT disease were poor and it is considered that improvement of intraoperative myocardial protection and aggressive use of postoperative circulatory support are necessary in the future. The survival cases of those who could endure surgery was comparatively satisfactory, but when cardiac event developed, prognosis was poor and thus more rigid follow-up is considered to be necessary.