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The serial measurement of postoperative serum enzymes has been proposed as an important method for identifying myocardial infarction following aortocoronary graft surgery. Serum glutamic oxalacetic transaminase, creatine phosphokinase and lactic dehydrogenase levels were determined during the initial five days following direct coronary artery surgery in 112 patients. Enzyme test results were analyzed by frequency distribution plots. Twelve patients (10.7%) developed definite electrocardiographic evidence of myocardial infarction within two weeks of surgery, seven on the first postoperative day. A general correlation of higher serum enzyme values and electrocardiographic evidence for myocardial infarction was established. However, the use of arbitrarily selected 90th percentile enzyme levels yielded a substantial number of false-negative and falsepositive results as compared with electrocardiographic diagnosis. The 90th percentile levels were substantially higher following multi-vessel surgery, compared with single-vessel surgery. Thus, analysis of serum enzymes following coronary surgery was found to be a useful, but not definitive adjunct in identifying patients suspect for operative infarction.

Seventeen patients received placebo medication during a 12-week run-in period, followed by four double-blind study periods of six weeks each, during which time placebo, 80 mg, 160 mg and 320 mg propranolol dosages were administered. Examination of the frequency of angina episodes and nonprophylactic nitroglycerin consumption revealed significant beneficial clinical responses for both the 160 and 320 mg dosages. Exercise testing also demonstrated increased exercise tolerance (320 mg dose) with a shift of the exercise end point from pain to fatigue in seven of 17 patients. The interrelationships between propranolol daily dosage, clinical response assessed by percent reduction in anginal episodes, beta-adrenergic blockade measured by percent reduction in exercise heart rate and serum levels were examined. In general, serum levels of 30 ng/ml, when drawn 90 to 180 minutes following the last oral dose, were required to achieve a 25% or greater reduction in angina frequency. Serum levels above 30 ng/ml were similarly correlated with a 20% or greater reduction in exercise heart rate at equivalent levels of exercise. Detailed examination of different patterns of clinical response with respect to beta-blockade, serum levels and oral doses are presented.

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