Early and late healing responses of normal XXXX artery to excimer laser irradiation.

@entity1 @entity3278 @entity731 @entity235 @entity5072 @entity26730 @entity439 @entity3440 @entity544 @entity715
Acute in vitro histologic studies have shown that the pulsed @entity26730 excimer laser causes precise microablation without the surrounding thermal tissue injury associated with frequently used continuous-wave lasers such as the argon, @entity544 , and @entity3278 :yttrium aluminum garnet lasers. However, the in vivo healing response of artery wall to excimer laser injury is not known. Accordingly, a @entity26730 excimer laser (308 nm, 40 nsec pulse width, 39 mJ/mm2/pulse) was transmitted via a 600 micron fused @entity3440 fiber to create 420 craters of varying depths (30 to 270 micron) in 21 normal @entity235 femoral and carotid arteries. At 2 hours, 2 days, 10 days, and 42 days after excimer laser ablation, the artery segments were perfusion fixed in situ and analyzed by light, scanning, and transmission electron microscopy. At 2 hours, craters were covered by a carpet of platelets and entrapped red blood cells. Fibrin and exposed collagen fibers were seen at the crater base. There was a sharp demarcation of the crater-artery wall interface without lateral laser tissue injury. At 2 days, adherent platelets persisted with @entity715 covering the base of the craters. Early healing responses were present, consisting of polymorphonucleated leukocytes and new endothelial cells, which extended over the crater rims. At 10 days, no thrombi were seen, and healing continued with almost complete reendothelialization. Macrophages, fibroblasts, fibrin, and entrapped red blood cells were present below the reendothelialized surface. At 42 days, healing was complete with obliteration of the craters by fibrointimal ingrowth. The surface was completely covered by a smooth monolayer of axially aligned endothelial cells. There were no @entity439 or surface @entity5072 responses. These favorable healing responses in normal @entity235 arteries suggest that pulsed lasers with high tissue absorption coefficients, such as the @entity26730 excimer laser, may be suitable energy sources for clinical laser angioplasty procedures. However, further studies in @entity731 animals are required before @entity1 clinical responses can be accurately predicted.
