Arterial response to laser operation for removal of atherosclerotic plaques

The cellular response of normal and atherosclerotic aortic intima after exposure in vivo to a 0.9 mm diameter carbon dioxide laser was examined in hypercholesterolemic swine with light and electron microscopy to evaluate tissue damage, thrombosis, and healing. At energy levels of greater than 5 joules, laser burns appeared as craters less than 1 mm in depth and 2 mm in diameter. Two days after the operation, craters were filled with platelet-fibrin thrombi that did not protrude above the level of adjacent endothelium. The internal elastic lamina was exposed 1 to 2 mm around the crater. This area was surrounded by a ring of densely packed leukocytes at the edge of the normal endothelium. Two weeks after the operation, the depressed crater surface was mostly reendothelialized with small, closely packed endothelial cells. The subjacent thrombus contained numerous phagocytic cells with inclusion of fibrin, erythrocytes, and membranous debris. Proliferative invaginations containing medial smooth muscle cells, mitotic figures, and collagen extended into the pit from the lateral aspects. Eight weeks after the operation, the burned area was still depressed and therefore less occlusive than adjacent lesion areas, and a fibrous cap had formed over the remaining necrotic area. The results suggest that a focused, low-energy carbon dioxide laser can be used to remove focal atherosclerotic plaques from arteries without inducing excessive thrombogenicity. Rapid healing, including reendothelialization and intimal fibrous scarring, with minimal damage to surrounding tissue, was observed.