Mitchell, David Charles; (1992) Laser assisted angioplasty of occlusive lower limb arterial disease using the pulsed dye laser. Doctoral thesis (M.S.), University College Hospital Medical School.

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Abstract

Energy produced by the pulsed dye laser, operating at wavelengths of 480 and 504 nm, is preferentially absorbed by atherosclerotic plaque. This observation was the starting point for this thesis which examines the potential of using laser energy as the single modality for achieving recanalisation and comparing this to standard balloon dilatation. In an atherosclerotic rabbit model, there was slightly improved vessel patency on angiography in the laser treated group. Histological morphometry was not found to give meaningful results due to wide variation in measurement produced in preparation of histological sections. Platelet deposition onto treated surfaces was examined and found not to differ between laser and balloon angioplasty. Administration of 6-carotene to rabbits leads to preferential plaque uptake, which resulted in a marked decrease in laser ablation threshold and more effective ablation of stained plaque compared to control. Percutaneous transluminal angioplasty can treat arterial occlusions with lesser mortality, but success in longer occlusions, over 7 cm, is less likely and there is a 30% - 50% restenosis rate at six months, which is thought to be due to the injury caused by the stretching of the arterial wall and splitting of atherosclerotic plaque during angioplasty. A clinical series of 78 limbs with occlusive peripheral arterial disease were treated by laser angioplasty using ball-tipped optical fibres backloaded into balloon dilatation catheters. Technical success was 74% and clinical success 59%, but was lower in those with heavily calcified arteries. Cumulative vessel patency was 67% at 6 months, 45% at one year and 42% at 18 months. Bench studies examined the ability of these new devices to ablate vascular tissue and found that although preferential plaque ablation was maintained, the ball-tipped and multi-fibre catheters were unable to ablate calcified plaque. The clinical study demonstrated the efficacy of laser angioplasty in the treatment of long arterial occlusions. However, success is hampered by lack of suitable delivery devices, and further design improvements are urgently required.

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