Comparisons of the effects on survival after coronary artery surgery in subgroups of patients from the Seattle Heart Watch.

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Abstract
The survival of medically and surgically treated coronary artery disease patients was compared in subgroups of patients to determine those most or least likely to benefit from surgery after an average of 5.5 yr of follow-up. Cox''s regression model for survival analysis was used in conjunction with data from all patients to estimate and test for the significance of the effects of surgery on survival in subgroups of patients, defined by 1 or more of the following variables: number of stenotic vessels (.gtoreq. 70%), ejection fraction, age, heart murmur, diuretic therapy, ventricular arrhythmia on resting ECG, left main coronary artery stenosis .gtoreq. 50%, previous myocardial infarction, cardiomegaly, congestive heart failure, unstable angina and functional class. The Cox model adjusts for differences between medical and surgical patients in variables shown to be predictive of survival. A statistically beneficial effect of surgery on survival was seen in patients with 2 or 3 vessel disease, ejection fraction .gtoreq. 30%, age .gtoreq. 48 yr, no heart murmur, no diuretic therapy, no ventricular arrhythmia on resting ECG, left main coronary artery stenosis < 50%, no cardiomegaly and no congestive heart failure. The converse subgroups defined by these variables did not show a significant beneficial effect from surgery. Patient subgroups defined by presence or absence of prior myocardial infarction or unstable angina and New York Heart Association functional class I-II vs. III-IV showed beneficial effects from surgery.