Coronary distensibility index measured by computed tomography is associated with the severity of coronary artery disease

Background Atherosclerotic changes within the coronary artery wall can affect vessel distensibility. Objective This study evaluated the relationship between the coronary distensibility index (CDI) and the severity of coronary artery disease (CAD) measured by computed tomographic angiography (CTA). Methods One hundred thirteen subjects, age 63 ± 10 years, 32% women, who underwent coronary artery calcium (CAC) scanning and CTA, were studied. Early diastolic and mid diastolic (MD) cross-section area (CSA) of the left anterior descending (LAD) artery were measured 5 mm distal to the left main bifurcation. CDI was defined as Δlumen CSA/[lumen CSA in MD × estimated central pulse pressure (eCPP)] × 103 {eCPP = 0.77 × peripheral pulse pressure}. LAD diameter measured by CTA and quantitative coronary angiography (QCA) was compared in 19 subjects without CAD. CAD was defined as normal (no stenosis and CAC 0), mild (stenosis ≤ 30%), moderate (stenosis 31%–69%), and severe (stenosis ≥ 70%) on CTA. Results Excellent correlation was observed between CTA and QCA measured by CDI ( r2 = 0.96, P = 0.0001). CDI decreased from normal coronaries (6.75 ± 1.43) to arteries with mild (5.78 ± 1.45), moderate (3.96 ± 1.06), and severe (3.31 ± 1.06) disease ( P = 0.004). The risk factor adjusted odds ratio of lowest versus 2 upper tertiles of CDI was 1.28 for mild, 8.47 for moderate, and 10.59 for severe CAD compared with the normal cohort. The area under the ROC curve to predict obstructive CAD (stenosis ≥ 50%) increased significantly from 0.71 to 0.84 by addition of CDI to CAC ( P < 0.05). Conclusion CTA-measured CDI is inversely related to the severity of CAD independent of age, sex, cardiovascular risk factors, and CAC.