Regional Coronary Endothelial Function is Related to Coronary Wall Eccentricity on MRI

Introduction: Coronary endothelial function (CEF) in patients with coronary artery disease (CAD) varies among coronary segments in a given patient for reasons that are incompletely understood. Hypothesis: Because both plaque eccentricity and coronary endothelial dysfunction are associated with adverse outcomes, we used noninvasive MRI to test the hypothesis that local coronary endothelial dysfunction is associated with local plaque eccentricity. Methods: We studied 13 healthy subjects (mean age±SEM: 55±7 years) and 21 patients with known CAD or CAD risk factors (61±4 years). To measure CEF, 3T coronary MRI was performed before and during isometric hand-grip exercise (IHE), a known endothelial-dependent stressor and % coronary cross-sectional area (CSA) and % coronary flow velocity (CFV) changes were measured. Black blood imaging of the coronaries was performed at the same cross sectional plane to quantify mean coronary wall thickness (CWT) and coronary eccentricity index (EI=max wall thickness (WT)-min WT)/max WT). Results: The changes in stress-induced CSA and CFV were significantly higher in healthy subjects (11.0±4.9% and 32.2±10.6% respectively) than in patients (2.2±1.5%, 12.8±4.9%, p<0.01 vs. healthy for both measures). Both mean CWT (1.11±0.06mm) and EI (0.47±0.2) were significantly lower in the healthy group than in the patients (CWT=1.59±0.07mm,p<0.001; EI= 0.57±0.02,p=0.006 vs. healthy). In the patient group, we observed a strong inverse relationship between stress-induced %CSA change and EI (r 2 =0.65, p<0.0001), but no significant relationship between %CFV change with stress and EI (r 2 =0.007,p=0.7). CWT was also significantly related to %CSA change (r 2 =0.47,p=0.002). Conclusion: We observed a strong inverse relationship between coronary endothelial macrovascular reactivity as measured by stress-induced %CSA change and the degree of coronary wall eccentricity in CAD patients. These findings indicate that an eccentric pattern of coronary wall remodeling is associated with abnormal local CEF, and therefore that anatomic and physiologic early indicators of coronary vascular pathology are closely related in atherosclerosis.