Objective: Inflammation and structural factors such as a thin fibrous cap, positive remodeling and large lipid pool have been established as factors associated with coronary plaque instability. This study aimed to investigate the hypothesis that the differential in coronary artery compliance between stenotic and adjacent arterial segments is another factor associated with unstable coronary disease.
Methods: Forty-one patients undergoing a percutaneous coronary intervention were classified as unstable coronary syndrome (n=19) or stable angina (n=22). Intravascular ultrasound was used to assess external elastic lamina (EEL) cross-sectional area at diastole and systole. Aortic pressure was determined from the coronary guiding catheter. Coronary cross-sectional compliance (C) was calculated as the quotient of systolic-to-diastolic area differential and pulse pressure. C was measured within the stenosis and the adjacent reference segments.
Results: EEL cross-sectional area was greater in systole than in diastole in the reference segments, but did not differ within the lesion site. C was greater in the distal reference than the stenotic segments (7.7+/-13.1 vs. 0.0+/-12.3mm(2)mmHg(-1)x10(3), p=0.003). When dichotomized by clinical presentation, the distal-to-stenosis compliance difference was only significant in the unstable coronary syndrome group (stable: distal 4.1+/-13.3 vs. stenosis -0.3+/-13.2mm(2)mmHg(-1)x10(3), ANOVA p=0.48; unstable: distal 11.9+/-11.9 vs. stenosis 0.1+/-11.6mm(2)mmHg(-1)x10(3), ANOVA p=0.006, distal-to-stenosis difference p=0.001).
Conclusions: A difference between stenotic and distal reference segment coronary compliance was evident in unstable, but not stable coronary artery disease patients. Coronary compliance differential would increase cyclical forces in the plaque shoulder region, which may contribute to plaque disruption.