Many Elective Angiographies Are Deemed Unnecessary

NEW ORLEANS — Nearly two-thirds of 400,000 patients who underwent elective diagnostic coronary angiography recently at 601 U.S. hospitals turned out not to have obstructive coronary artery disease.

This is not an efficient use of health care resources, and a clear factor in this poor performance is the low positive predictive value of current noninvasive stress testing methods for myocardial ischemia, Dr. Manesh R. Patel said at the annual scientific sessions of the American Heart Association.

Clinical practice guidelines recommend documenting ischemia through noninvasive stress testing before considering diagnostic coronary angiography. That was done in 84% of the cases in this series, taken from the American College of Cardiology National Cardiovascular Data Registry. However, the positive predictive value of noninvasive testing was just 41%, said Dr. Patel of Duke University, Durham, N.C. “There appear to be opportunities to improve the efficiency of diagnostic strategies in contemporary practice,” he said.

He reported on 397,954 stable patients without a history of acute coronary syndrome or coronary revascularization who underwent diagnostic coronary angiography during 2004-2008 and were entered into the comprehensive national registry.

Obstructive coronary artery disease (CAD) was detected in 37.5% of patients based on at least a 50% stenosis of the left main artery or a 70% or greater stenosis of other major vessels.

Of the patients with obstructive CAD, 14% had a low Framingham risk score, 59% were at moderate Framingham risk, and 27% were at high risk. Among those patients found not to have significant CAD, 39% had a low Framingham risk score, 52% had a moderate risk score, and the rest had a high Framingham score.

Among the 69% of subjects who were referred for angiography following a positive stress test, 41% proved to have obstructive CAD. Of the 12% of patients who were sent for diagnostic angiography after a negative stress test, 28% were found to have obstructive CAD.

A total of 16% of patients in this large series were referred for diagnostic angiography without a prior stress test, presumably because something in their clinical evaluation caused their physician to believe they had a high likelihood of significant CAD. Yet upon angiography, only 35% of this group proved to have obstructive CAD.

Thus, neither Framingham risk score nor stress test results were very useful as a guide to who ought to have diagnostic angiography. Nor were patient symptoms. For example, 44% of patients found to have obstructive CAD had stable angina, but so did 27% of those who did not. Atypical chest pain, reported by 37% of patients, was present in 25% of those found to have obstructive CAD and in 44% who did not.

Complications of diagnostic angiography occurred in 1.6% of cases.