Patients with unstable coronary syndromes often have complex morphology of coronary stenoses at angiography. We evaluated the association between qualitative assessment of coronary stenoses and plaque inflammation determined by immunohistochemistry.

A total of 79 patients with unstable (n = 46) or stable angina (n = 33) underwent directional coronary atherectomy for culprit lesions. Qualitative analysis of coronary angiograms was performed using a modified Ambrose classification. Coronary lesions were categorized as either simple (concentric and eccentric type I, n = 29) or complex (eccentric type II and multiple irregularities, n = 50). Cryostat sections of retrieved atherosclerotic specimens were stained immunohistochemically with monoclonal antibodies, ⍺-actin (smooth muscle cells), CD68 (macrophages), and CD3 (T lymphocytes). The extent of atherosclerotic inflammation within each coronary lesion was determined by the percentage of immunopositive macrophages per total tissue area (including smooth muscle cells) and the number of T lymphocytes per mm².

The mean (± SD) percentage of macrophages in atherectomy specimens from patients with unstable angina was greater than in specimens from patients with stable angina (21% ± 14% vs. 13% ± 10%, P = 0.01); similar results were seen when complex coronary lesions were compared with simple lesions (23% ± 13% vs. 9% ± 8%, P <0.001). In multivariate linear regression models, the combination of unstable angina and lesion complexity was strongly associated with the percentage of plaque macrophages.

The extent of atherosclerotic plaque inflammation is associated with angiographic grading of coronary lesion complexity and unstable angina.