Quantification of nonculprit coronary lesions: Comparison of cardiac 64-MDCT and invasive coronary angiography

OBJECTIVE. The purpose of our study was to evaluate the accuracy of cardiac 64-MDCT to quantify the grade of stenosis of nonculprit lesions. SUBJECTS AND METHODS. Twenty-nine consecutive patients (23 men and six women; mean age, 62 ± 10 years) presenting with acute coronary syndrome (ACS) had nonculprit coronary lesions of ≥ 30% stenosis quantified on quantitative coronary angiography (QCA). Five 64-MDCT postprocessing techniques (maximum intensity projection [MIP], multiplanar reformat [MPR], cross-sectional area [CSA], and diameter and area derived from semiquantitative coronary software) were used to grade lesions. Two separate groups of two independent readers analyzed QCA and cardiac CT images using a 17-segment model. Coronary angiography was the reference standard. RESULTS. Nonculprit lesions were identified in 46 analyzable coronary segments. Subgrouping lesions on the basis of reference vessel diameter resulted in strong correlations for quantifying nonculprit lesions in vessels > 3 mm (R = 0.78-0.91, p < 0.01) but poor correlations for nonculprit lesions in vessels ≤ 3 mm (R = 0.1-0.07). Subgrouping lesions on the basis of plaque type resulted in poor correlations for calcified plaques (R = 0.01-0.30) but moderate to strong correlations for mixed (R = 0.58-0.75, p < 0.01) and noncalcified (R = 0.44-0.61, p < 0.01) plaques. The best overall correlation among all CT techniques with QCA was CSA (R = 0.56, p < 0.01). Interobserver agreement (kappa values) for MPR, MIP, coronary software diameter and area were 0.6, 0.7, 0.62, and 0.57, respectively. CONCLUSION. In patients presenting with ACS, 64-MDCT provided an accurate grade of stenosis for nonculprit coronary lesions in proximal coronary segments. Calcified plaques and lesions in coronary segments ≤ 3 mm diameter remained difficult to accurately quantify.