Coronary artery compliance and adaptive vessel remodelling in patients with stable and unstable coronary artery disease

Objective-To test the hypothesis that patients with unstable coronary syndr omes show accentuated compensatory vessel enlargement compared with patient s with stable angina, and that this may in part be related to increased cor onary artery distensibility. Design and patients-In 23 patients with unstable coronary syndromes (10 wit h non-Q wave myocardial infarction and 13 with unstable angina), the culpri t lesion was investigated by intravascular ultrasound before intervention. The vessel cross sectional area (VA), lumen area (LA), and plaque area (VA minus LA) were measured at end diastole and end systole at the lesion site and at the proximal and distal reference segments. Similar measurements wer e made in 23 patients with stable angina admitted during the same period an d matched for age, sex, and target vessel. Calculations were made of remode lling index (VA at lesion site divided by VA at reference site), distensibi lity index ([(Delta A/A)Delta P] x 10(3), where Delta A is the luminal area change in systole and diastole and Delta P the difference in systolic and diastolic blood pressure measured at the tip of the guiding catheter during a cardiac cycle), and stiffness index beta ([ln(P-svs/P-diss)]/(Delta D/D) , where P-svs is systolic pressure, P-diss is diastolic pressure, and Delta D is the difference between systolic and diastolic lumen diameters). Posit ive remodelling was defined as when the VA at the lesion was > 1.05 times l arger than at the proximal reference site, and negative remodelling when th e VA at; the lesion was < 0.95 of the reference site. Results-Mean (SD) LA at the lesion site was similar in both groups (4.03 (1 .8) v 4.01 (1.93) mm(2)), while plaque area was larger in the unstable grou p (13.29 (4.04) v 8.34 (3.6) mm(2), p < 0.001). Remodelling index was great er in the unstable group (1.14 (0.18) v 0.83 (0.15), p < 0.001). Positive r emodelling was observed in 15 patients in the unstable group (65%) but in o nly two (9%) in the stable group (p < 0.001). Negative remodelling occurred only in two patients with unstable symptoms (9%) but in 17 (74%)) with sta ble symptoms. At the proximal reference segment, the difference in Lh betwe en svstole and diastole was 0.99 (0.66) mm(2) in the unstable group and 0.3 9 (0.3) mm(2) in the stable group (p < 0.001), and the calculated coronary artery distensibility was 3.09 (2.69) and 0.94 (0.83) per mm Hg in unstable and stable patients, respectively (p < 0.001). The stiffness index beta wa s lower in patients with unstable angina (1.95 (0.94) v 3.1 (0.96), p < 0.0 01). Conclusions-Compensatory vessel enlargement occurs to a greater degree in p atients with unstable than with stable coronary syndromes, and is associate d with increased coronary artery distensibility.