Thermal laser probe angioplasty: influence of constant tip temperature, plaque composition, and probe/vessel diameter ratio.
Thermal laser angioplasty uses constant laser power, producing widely variable tip temperatures in vivo. Results have been suboptimal. We studied the effect of 50-400 degrees C tip temperatures on depth of ablation at 192 sites on plaqued and normal human aorta in vitro, and the angiographic and histologic response in vivo of 300-400 degrees C at probe/vessel ratios of 0.5-1.0, in 40 normal canine femoral artery segments. In vitro, there was a direct relationship between tip temperature and depth of ablation, r = 0.71 (all segments), r = 0.74 for fibrous plaque, but a poor correlation in fatty plaque r = 0.35. In fibrous plaque, there was proportionately more ablation at tip temperatures greater than 300 degrees C, mean depth 0.62 mm, than at 150-300 degrees C, mean 0.37 mm, (P less than .001). Ablation was similar in plaqued and normal aorta. In vivo, 300 degrees C, 350 degrees C, and 400 degrees C produced similar effects. At probe/vessel ratios less than 0.8, only disruption of internal elastic lamina was observed. At ratios greater than or equal to 0.8, spasm occurred in 39% (7/18), transmural damage in 28% (5/18), and perforation in one of 18. Ablation is not selective for plaque and is highly variable in fatty plaque. Tip temperatures above 300 degrees C produce greater ablation than at lower temperatures. In clinical applications, probe/vessel rations less than or equal to 0.7 may be most appropriate, and it appears that thermal remodeling may contribute more to outcome than plaque ablation.
Vincent
G M
GM
Department of Medicine, LDS Hospital, Salt Lake City, UT 84143.
Fox
J
J
Johnson
M D
MD
Strickland
R
R
Garry
S L
SL
Hammond
E
E
D016342:Angioplasty, Laser / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D000818:Animals; D001011:Aorta / Q000473:pathology / Q000601:surgery*; D001027:Aortography; D001161:Arteriosclerosis / Q000473:pathology / Q000601:surgery*; D004285:Dogs; D006801:Humans; D066298:In Vitro Techniques; D012016:Reference Values; D013696:Temperature