Assessing intermediate coronary lesions: angiographic prediction of lesion severity on intravascular ultrasound

Intravascular ultrasound (IVUS) can detect atherosclerotic compromise in coronary segments where conventional angiography cannot. However, IVUS is more invasive, expensive and laborious than angiography. We compared the detection of stenosis by IVUS and angiography and identified angiographic predictors of severe luminal stenosis on IVUS in patients with angiographically-intermediate coronary lesions.

Fifty-six patients with myocardial ischemia and intermediate stenosis by quantitative coronary angiography (QCA) underwent IVUS assessment of the culprit artery. The results from IVUS and QCA were compared using the two-tailed unpaired t-test. Multiple regression analysis was performed to identify QCA parameters that could predict the presence of severe stenosis on IVUS, defined as a minimum luminal area (MLA) < or = 4 mm2.

A total of 63 stenotic coronary lesions were classified as intermediate by QCA; 68% of these were found to be severe on IVUS. There was a weak correlation between IVUS and QCA with respect to percentage of stenosis, minimum luminal diameter, reference segment diameter and length of atherosclerotic compromise. In contrast, there was a significant difference in the assessment of reference segment luminal diameter, which was 2.83 +/- 0.56 mm by angiography versus 3.45 +/- 0.69 mm by IVUS (p < 0.0001). The only angiographic predictor of the presence of severe coronary stenosis on IVUS was a distal reference segment diameter < or = 2.42 mm.

In patients with angiographically-intermediate lesions, the frequency of severe stenosis detected by IVUS was high, indicating that angiography underestimated the severity of stenosis. Distal reference segment diameter was the only predictor of a small MLA and could be used to stratify these lesions into groups with higher and lower risk of severe stenosis.