The prognostic significance of 50% coronary stenosis in medically treated patients with coronary artery disease.

In this study we determined the prognostic significance of 50% coronary stenosis in 1183 medically treated patients with coronary artery disease. Clinical outcome was measured by survival and event- free (freedom from death and infarction) rates. Significant disease was first defined as 75% or greater narrow- ing. In 225 patients with less than 75% narrowing of all vessels, including 68 patients with 50% stenosis of at least one vessel, the 3-year survival rate was 100%. Patients with one, two or three significantly (75% or greater) stenosed vessels with additional 50% stenosed vessels had the same outcome as patients with one, two or three diseased vessels without additional 50% stenosed vessels. Significant disease was then defined as 50% or greater narrowing. Patients with significant (50% or greater) stenosis of one, two and three vessels and the left main coronary artery were divided into those in whom all diseased vessels were 75% or greater stenosed (group A) and those in whom at least one vessel was only 50% stenosed (group B). In every category, group B patients had a better outcome than group A patients. The largest differences were in three-vessel and left main coronary artery disease. Group B patients also had lower prevalences of previous infarction and abnormal ven- tricular function than group A patients. In three-vessel disease, the differences in outcome between group A and group B patients remained significant in multivariable analyses with descriptors of left ventricular function. Thus, 50% coronary stenosis is associated with less risk than 75% or greater stenosis even after adjustment for left ventricular function. When 50% stenosis is defined as significant, subsets based on the number of diseased vessels may be heterogenous with respect to baseline characteristics and outcome.