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 eventfree (freedom from death and infarction) rates. Significant disease was first defined as 75% or greater narrowing. 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 ventricular 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.