The influence of plaque orientation (pericardial or myocardial) on coronary arterial remodeling

Background: Many systemic, regional and lesion factors have been identified which may influence arterial remodeling, but little is known about the importance of extravascular resistance to vessel enlargement. As myocardial systolic splinting may significantly affect vessel expansion the effect of plaque orientation on arterial remodeling in eccentric coronary atherosclerotic lesions was examined. Methods: Using intravascular ultrasound imaging to obtain cross-sectional vessel area (VA), plaque area (PA) and lumen area (LA), remodeling in eccentric left anterior descending coronary artery lesions was compared which predominantly involved the pericardial or free arc (P, n=25) and the myocardial side (M, n=40) of the vessel wall. Normalized vessel area (NVA, VAlesion/VAreference) was compared as a continuous and categorical variable (positive>1.05, intermediate 0.95–1.05, negative<0.95) as well as remodeling index (RI, VAlesion−VAreference/PAlesion−PAreference). Results: The two groups were well matched for clinical and lesion characteristics known to affect remodeling. Reference segments areas were similar in the two groups; while lesion LA was also similar, in the pericardial group there was significantly greater lesion PA (P 12.78±0.72, M 10.26±0.50 mm2, P<0.05) and VA (P 15.71±0.90, M 12.82±0.57 mm2, P<0.05) demonstrating enhanced compensatory remodeling. Outward remodeling was significantly greater in P than in M by both NVA (P 1.03±0.03, M 0.86±0.03, P<0.01) and RI (P 0.02±0.07, M −1.10±0.32, P<0.01). Positive, intermediate and negative remodeling occurred in nine, nine and seven lesions in P and in four, ten and 26 lesions in M (P<0.01). Conclusions: Remodeling compensates more for plaque growth in eccentric coronary lesions which are surrounded by the pericardium than those surrounded by the myocardium. Extravascular resistance appears to influence arterial remodeling.