Factors influencing mortality and myocardial infarction after coronary artery bypass grafting.

Although the mortality for coronary artery bypass graft surgery has declined, some categories of patients are still recognized as being at greater risk. Because the mortality, even for most patients with risk factors, is less than 10%, evaluating this risk and any improvement arising from changing techniques requires thousands of cases. The need for these large patient numbers makes the evaluation of changes difficult. Even when other risk factors are accounted for in the mortality estimate, the patient's age remains an important factor, although there is no obvious reason why this should be so. Similarly, female sex is well recognized as a risk factor. However, the tendency for women to have a smaller body surface area and corresponding smaller arterial diameters may be the explanation. Perfusion time appears to have a strong influence on mortality after it exceeds about 90 minutes, and a similar influence on myocardial infarction also appears to be present. The increased risk of myocardial infarction with unstable angina may relate to disruption of the normal endothelial vasodilatation caused by nitric oxide.