INTRAVASCULAR ULTRASONIC EVIDENCE FOR IMPORTANCE OF PLAQUE DISTRIBUTION (ECCENTRIC VS CIRCUMFERENTIAL) IN DETERMINING DISTENSIBILITY OF THELEFT ANTERIOR DESCENDING ARTERY

Although previous studies have shown that coronary atherosclerosis is accompanied by impaired vessel wall compliance, few data exist regardi ng the regional vessel distensibility that may be important in order t o gain an insight into the mechanism of atherosclerotic plaque rupture . Therefore, we analyzed 45 coronary sites of the proximal left anteri or descending artery from 40 patients. Using intravascular ultrasound, luminal area in diastole (A) and in systole was measured at the disea sed sites. With the ratio of luminal area changes (dA) to coronary pre ssure changes (dP) during a cardiac cycle, the total distensibility in dex was obtained by the formula: [(dA/A)/dP] x 10(3). At the sites wit h noncircumferential disease perimeters in diastole (L) and in systole were measured at the normal and narrowed portions. Using the changes in perimeters (dL) during a cardiac cycle, the regional distensibility index was obtained by the formula: [(dL/L)/dP] x 10(3). In 22 sites w ith circumferential disease, the total distensibility index was 1.03 /- 0.61 mm Hg (mean I SD), and significantly lower then that from 23 s ites with noncircumferential disease that showed 1.45 +/- 0.89/mm Hg ( p <0.05). In noncircumferential disease, the regional distensibility i ndex at narrowed portions wets significantly lower, 0.33 +/- 0.47/mm H g, than that at normal portion, 1.11 +/- 0.75/mm Hg (p <0.01), suggest ing the heterogenous distribution of regional wall distensibility in n oncircumferential lesions. These results indicate that the heterogeneo us regional wall distensibility exists at the sites with noncircumfere ntial disease where the total vessel distensibility is preserved by th e presence of the compliant normal portion. (C) 1997 by Excerpta Medic o, Inc.