Conditional probability of multiple coronary graft failure.

To assess the potential capability of using artery-specific factors to predict the success of coronary bypass grafting, we classified each graft according to the type of graft (mammary, single vein, or multiple skip vein), the degree of obstruction in the native coronary artery, and the size of the grafted artery. The mean patency rates for each category of graft were determined by performing early postoperative (mean 6.6 months) arteriograms in 354 patients. We found that mammary arteries gave the best results for every graft category. Skip vein grafts had a higher mean patency rate than single vein grafts for arteries with obstructions between 70% and 90% and lumina less than 2.0 mm in diameter. The results for vein and skip grafts were equivalent for the category with arteries greater than 2.0 mm and obstruction greater than 90%. Vein grafts produced better results than skip grafts for the remaining categories. Patients were classified into subgroups according to the number of actually observed graft failures. The probabilities that specific numbers of grafts would fail were calculated for each patient. These probabilities were based upon the observed patency rates for the category appropriate for each graft and the hypothesis that individual grafts within a patient fail independently. We observed an excess number of patients with no failures or multiple failures than would be expected according to the hypothesis of independent failure and category-specific patency rates. Conversely, there were fewer patients than expected who had single failures. Therefore, we postulate that there may also be global factors which influence early graft patency.

Association between early graft patency and late outcome for patients undergoing artery bypass graft surgery.

For a group of 658 patients who received coronary artery bypass graft surgery, we investigated the correlation between the degree of early (6 months) graft patency and recurrence of anginal symptoms, late myocardial infarction, and postoperative coronary-related death. The patients were grouped according to the number of surgically placed grafts, and each group was further subgrouped on the basis of the number of grafts functioning at the early postsurgical follow-up examination. The patients were observed over a period as long as 13 years. The frequency with which angina returned correlated significantly with the degree of patency within each of the groups (one, two, three, or four grafts); patients with a higher percentage of patent grafts experienced longer periods of freedom from angina. On the average, patients with all of their multiple grafts patent experienced at least 7 more years of symptomatic relief than their counterparts with all grafts occluded. Most surprisingly, the rate of the return of angina for those patients who had all grafts patent and were completely revascularized was independent of the number of diseased vessels or the number of grafts placed. The findings for coronary death and postoperative infarction showed similar trends.