Background—Lipid-rich, inflamed atherosclerotic lesions are associated with plaque rupture and thrombosis, which are the most important causes of death in patients with diabetes mellitus. This study was designed to quantify lipid composition and macrophage infiltration in the coronary lesions of patients with diabetes mellitus.

Methods and Results—A total of 47 coronary atherectomy specimens from patients with diabetes mellitus were examined and compared with 48 atherectomy specimens from patients without diabetes. Plaque composition was characterized by trichrome staining. Macrophage infiltration was characterized by immunostaining. Clinical and demographic data were similar in both groups. The percentage of total area occupied by lipid-rich atheroma was larger in specimens from patients with diabetes (7±2%) than in specimens from patients without diabetes (2±1%; P=0.01), and the percentage of total area occupied by macrophages was larger in specimens from patients with diabetes (22±3%) than in specimens from patients without diabetes (12±1%; P=0.003). The incidence of thrombus was also higher in specimens from patients with diabetes than in specimens from patients without diabetes (62% versus 40%; P=0.04). Plaque composition, macrophage infiltration, and thrombus were similar in lesions from diabetic patients treated with insulin compared with lesions from patients treated with sulfonylureas or diet.

Conclusions—Coronary tissue from patients with diabetes exhibits a larger content of lipid-rich atheroma, macrophage infiltration, and subsequent thrombosis than tissue from patients without diabetes. These differences suggest an increased vulnerability for coronary thrombosis in patients with diabetes mellitus.