As previously reported, unstable angina is usually related to characteristic coronary artery lesion's morphology analyzed by coronary angiogram. This takes the form of an eccentrically placed convex stenosis with a narrow neck due to one or more overhanging edges or irregular, scalloped borders, or both. Although most studies were done for lesions with high degree stenosis(>50%), recent studies emphasized the role of vulnerability of plaque in acute coronary syndrome and even mild degree stenotic lesions may progress rapidly to evoke acute coronary syndrome. Therefore in this study, we analyzed the morphological characteristics of coronary artery lesions with mild degree stenosis as well as severe stenosis.

We conducted a retrospective study of 96 patients with angina pectoris (42 of stable patients and 54 of unstable patients) who underwent coronary angiography. Each lesions with 25% or greater diameter stenosis were categorized into simple and complex lesion(convex intraluminal obstruction with a narrow neck or irregular borders, diffuse irregularities, ulceration, thrombus). Calcification of coronary artery, extents of lesions were analyzed and stenosis grade and location were categorized by AHA classification.

There were no significant differences between the stable angina and unstable angina in risk factors and vessel involvement, numbers of lesions, calcification and total obstruction. In morphologic analysis, complex lesions were more frequent in unstable angina than stable angina (49% vs 33%, p<0.05). The mean of percent diameter stenosis was not signigicantly different between two groups, but severe stenotic lesions with 90% or more stenosis were more frequent in unstable angina (34% vs 22%, p<0.05). Locations of involved vessels were similar between the angina groups. Complex lesions were distributed more frequent in RCA and simple lesions were more in LAD and LCX (p<0.05).

The lesions with both complex morphology and severe degree stenosis are closely implicated in unstable angina.