Superiority of the internal mammary artery as a coronary bypass graft

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There is controversy as to the ideal conduit for coronary bypass grafting. Claims have been made that the internal mammary artery is a better conduit, based on evidence of superior patency. In contrast, many feel the internal mammary artery graft is inferior because of limited flow rate and altered hemodynamics in flow. The clinical results, and not angiographic patency or physiologic measurement, remain the best means for determining superiority of an operative technique.

Analysis of our first 1000 patients, based on computerized data, proves the superiority of the internal mammary artery as a coronary artery bypass conduit. The follow-up of these patients varied from 2½ to 8 years, with an average follow-up of greater than 4 years. The study was complete to the present in 98% of patients. The operative success was judged by overall survival, relief of angina, prevention of congestive heart failure, and nonfatal myocardial infarction rates.

Three separate comparisons were made of the clinical success: (1) All patients who had the two types of graft were compared as to the presence of any variables indicating clinical results. (2) The groups were matched according to the actual vessels bypassed and the overall mortality rates were statistically compared. (3) Possible sources of error were eliminated by exclusion of biased subsets.

To determine the source of error, a distribution correlation of the two types of grafts among 195 independent clinical variables was studied. Uneven distribution was found in a number of independent variables. These maldistributed variables were then correlated with . . .



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