Coronary bypass surgery was performed on 439 patients between the years 1969 and 1973 (group A) and on 1,760 patients between the years 1974 and 1979 (group B). The operative mortality for group A was 3.9%; for group B, 1.3%; four-year survival for group A patients was 88.9%±1.5% (mean±SE); for group B patients, 92.5%±0.9%. The difference between the relative four-year survival rates (based on age- and sex-matched Oregon population) between groups B and A was 6.2%; the lower operative mortality would account for only 2.6%. We conclude that the results of coronary bypass surgery have improved because of (1) a lower operative mortality, and (2) other factors that cannot be precisely defined at the present time but probably are the long-term result of better and more complete operative and perioperative techniques.
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