Coronary artery disease is the leading cause of death among men and women in the United States. While invasive x-ray coronary angiography is the gold standard for identifying significant coronary artery disease, noninvasive techniques are more appropriate in patients with less severe disease. Kim and colleagues conducted a prospective, multicenter, international study to evaluate the clinical usefulness of magnetic resonance angiography (MRA) in the diagnosis of coronary artery stenosis.
They enrolled 109 patients at seven different study sites over the course of 16 months. The authors did not elaborate on what measures were in place to prevent a selection bias in the way patients were referred for MRA imaging. The MRA technique employed was designed to visualize up to the first 5 cm of each of the main coronary arteries. No distal evaluation of the main arteries or any side branches was possible. The average time to complete the imaging was 70 minutes; some scans required more than two hours. All patients underwent standard coronary angiography within two weeks of MRA, and the results were compared.
The ability of MRA to adequately assess the proximal coronary arteries ranged from 68 percent for the left circumflex to 93 percent for the right coronary artery. In patients with clinically significant disease evident by standard angiography (i.e., left main or three-vessel artery disease), MRA was 93 percent sensitive in corroborating these stenoses. The overall sensitivity in identifying any coronary artery stenosis of 50 percent or more of the luminal diameter was 88 percent, with a specificity of 58 percent.
The authors conclude that “this noninvasive approach reliably identifies (or rules out) left main coronary artery or three-vessel disease.”
editor's note: The publicity these results generate will no doubt lead to ever wider public advertisement of noninvasive coronary artery assessment, but the results should be interpreted with a critical eye. Examination times of more than two hours in some cases make it likely that the expense and inconvenience of MRA will approach that of standard angiography but without the same degree of accuracy. Missing clinically significant disease in 6 percent of cases and having a false-positive rate of up to 42 percent in identifying any coronary stenosis may or may not be acceptable, depending on one's point of view. Perhaps in patients with equivocal cardiac stress tests and lower clinical suspicion of coronary disease, a negative result from MRA would be useful because relatively few cases of left main or three-vessel disease would be missed.—b.z.