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The Journal of Thoracic and Cardiovascular Surgery, Vol 96, 150-156, Copyright © 1988 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
LG Prevosti, MB Leon, PD Smith, JT Dodd, RF Bonner, M Robinowitz, RE Clark and R Virmani
Acute in vitro histologic studies have shown that the pulsed xenon chloride
excimer laser causes precise microablation without the surrounding thermal
tissue injury associated with frequently used continuous-wave lasers such
as the argon, carbon dioxide, and neodymium:yttrium aluminum garnet lasers.
However, the in vivo healing response of artery wall to excimer laser
injury is not known. Accordingly, a xenon chloride excimer laser (308 nm,
40 nsec pulse width, 39 mJ/mm2/pulse) was transmitted via a 600 micron
fused silica fiber to create 420 craters of varying depths (30 to 270
micron) in 21 normal canine 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 thrombus 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 aneurysms or surface hyperplastic responses. These
favorable healing responses in normal canine arteries suggest that pulsed
lasers with high tissue absorption coefficients, such as the xenon chloride
excimer laser, may be suitable energy sources for clinical laser
angioplasty procedures. However, further studies in atherosclerotic animals
are required before human clinical responses can be accurately predicted.
ARTICLES
Early and late healing responses of normal canine artery to excimer laser irradiation
National Heart, Lung, and Blood Institute, Cardiology Branch, Bethesda, MD 20892.
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