50th anniversary historical article. Acute coronary syndromes: the degree and morphology of coronary stenoses

Local coronary wall eccentricity and endothelial function are closely related in patients with atherosclerotic coronary artery disease

BACKGROUND

Coronary endothelial function (CEF) in patients with coronary artery disease (CAD) varies among coronary segments in a given patient. Because both coronary vessel wall eccentricity and coronary endothelial dysfunction are predictors of adverse outcomes, we hypothesized that local coronary endothelial dysfunction is associated with local coronary artery eccentricity.

METHODS

We used 3 T coronary CMR to measure CEF as changes in coronary cross-sectional area (CSA) and coronary blood flow (CBF) during isometric handgrip exercise (IHE), a known endothelial-dependent stressor, in 29 patients with known CAD and 16 healthy subjects. Black-blood MRI quantified mean coronary wall thickness (CWT) and coronary eccentricity index (EI) and CEF was determined in the same segments.

RESULTS

IHE-induced changes in CSA and CBF in healthy subjects (10.6 ± 6.6% and 38.3 ± 29%, respectively) were greater than in CAD patients 1.3 ± 7.7% and 6.5 ± 19.6%, respectively, p < 0.001 vs. healthy for both measures), as expected. Mean CWT and EI in healthy subjects (1.1 ± 0.3 mm 1.9 ± 0.5, respectively) were less than those in CAD patients (1.6 ± 0.4 mm, p < 0.0001; and 2.6 ± 0.6, p = 0.006 vs. healthy). In CAD patients, we observed a significant inverse relationship between stress-induced %CSA change and both EI (r = -0.60, p = 0.0002), and CWT (r = -0.54, p = 0.001). Coronary EI was independently and significantly related to %CSA change with IHE even after controlling for mean CWT (adjusted r = -0.69, p = 0.0001). For every unit increase in EI, coronary CSA during IHE is expected to change by -6.7 ± 9.4% (95% confidence interval: -10.3 to -3.0, p = 0.001).

CONCLUSION

There is a significant inverse and independent relationship between coronary endothelial macrovascular function and the degree of local coronary wall eccentricity in CAD patients. Thus anatomic and physiologic indicators of high-risk coronary vascular pathology are closely related. The noninvasive identification of coronary eccentricity and its relationship with underlying coronary endothelial function, a marker of vascular health, may be useful in identifying high-risk patients and culprit lesions.

Accuracy and uniqueness of three in vivo measurements of atherosclerotic carotid plaque morphology with black blood MRI

High-resolution MRI provides unique information about morphology of atherosclerotic carotid plaque. In this study, the accuracy and precision of measurements of carotid plaque burden and lumen narrowing were determined for in vivo black blood MRI assessment with respect to ex vivo MRI in a group of 37 atherosclerosis patients who underwent carotid endarterectomy (CEA). Three different plaque measures were compared between paired in vivo and ex vivo MR images: maximum wall area (MWA), minimum lumen area (mLA), and wall volume (WV). MWA and WV are measures of plaque burden, while mLA is a measure of lumen narrowing. The matched in vivo and ex vivo measurements showed good agreement (the correlation coefficients for in/ex vivo WV, MWA, and mLA were 0.92, 0.91, 0.90, respectively) with predictable bias. This study indicates that in vivo black blood MRI can be used to directly estimate the morphology of the plaque. Comparison of the three plaque measures showed that mLA and MWA or WV provide different information regarding the atherosclerotic lesions (the correlation coefficients between mLA and MWA or WV were less than 0.3). Black blood MRI technique is a potentially powerful clinical tool to characterize the severity of atherosclerotic plaque. It can provide accurate measurements on different aspects of the plaque, from plaque burden to lumen narrowing.