Microvasculature of Carotid Atheromatous Plaques: Hemorrhagic Plaques Have Dense Microvessels with Fenestrations to the Arterial Lumen

Background Microvessels in atheromatous plaques are well known to play a role in plaque vulnerability associated with intraplaque hemorrhage, but their architecture remains unclear. The morphometry of the microvasculature and hemorrhage of human carotid atheromatous plaques (CAPs) were evaluated, and 3-dimensional (3D) reconstruction of the microvessels was performed. Methods CAPs were obtained by endarterectomy in 42 patients. The specimens were analyzed using light microscopy. Plaque hemorrhage was defined as an area-containing red blood cells (>1 mm2 ). To determine the histopathologic features of plaque hemorrhage, the plaque area was divided into 4 regions: cap, shoulder, lipid/necrotic core, and media. Then, the density of microvessels and macrophages in each region was quantified. Two representative lesions with either hemorrhagic or nonhemorrhagic plaque were cut into 90 serial sections. The sections were double stained with anti-CD34 and anti-α smooth muscle actin antibodies, scanned using a digital microscope, and reconstructed using TRI-SRF2 software. Results The hemorrhagic plaques showed a higher density of microvessels than nonhemorrhagic plaques in the shoulder, cap, and lipid/necrotic core ( P = .03, .009, and .001, respectively), and there was positive correlations between its density and macrophages in each regions ( P