Argon laser angioplasty with a laser probe

Abstract

A preliminary basic study of argon laser angioplasty with the use of a specially designed probe is presented. Arterial specimens were harvested from 10 amputated lower extremities. The studies included the evaluation of coaxial laser angioplasty in 10 partially or totally occluded arteries; the observation of the effect of perpendicularly applied laser energy on 35 thrombi, 54 soft and 10 hard atherosclerotic, and 51 normal arterial walls; the comparison of laser energy requirements for coaxial vessel lumen enlargement or recanalization vs. perpendicular penetration in 10 occluded, hard atherosclerotic arteries; and the spectrographic analysis of calcium density gradient in two specimens. The results showed that the power required for vessel lumen enlargement was 10 +/- 6 J/mm of atherosclerotic vessel (mean +/- standard deviation). The probe followed the original arterial lumen, did not perforate the vessel wall, and created a smooth, enlarged path. The power required to penetrate perpendicularly to a similar depth for thrombi, soft and hard atherosclerotic plaques, and normal arterial walls was 15 +/- 4, 30 +/- 15, 65 +/- 32, and 246 +/- 123 J/mm, respectively. In the hard calcified specimens, laser energy required for coaxial lumen enlargement or recanalization was significantly less than that for perpendicular penetration (p less than 0.05), which correlated with the calcium density map indicating an increase from inside to outside.

Effects of blood flow on laser probe temperature in human arteries

“…This apparent decreased efficiency of probe heat generation and thermal ablation in saline can possibly be explained by the fact that saline will remain at 100°C until water is vaporized [3,22]. Despite this, some have advocated adding a saline perfusion during laser angioplasty to minimize vessel wall injury and to improve laser penetration [20,23,24]. However, our findings suggest that saline may act as a heat sink, potentially reducing the effectiveness of the thermal probe by reducing its temperature.…”

“…Absorption of argon laser energy by blood results in lysis, membrane denaturation, and charring of red blood cells that fuse to form mesh-like conglomerates [25,26]. This char may then coat the laser probe [27] and may act as a n insulator to prevent heat transfer to the surrounding blood or the vessel wall [24]. Alternatively, the crust formed on the probe during lasing in blood may occlude the sapphire lens of an open-ended probe (such as was used in this study) and thus increase the amount of energy delivered to the metal cap.…”

Excimer Laser Ablation in the Treatment of Total Chronic Obstructions in Critical Limb Ischaemia in Diabetic Patients. Sustained Efficacy of Plaque Recanalisation in Mid-term Results

“…The idea of using laser energy to treat vascular obstruction dates back almost 30 years. 1,2 Early attempts failed in gaining proper diffusion: the technology used at that time relied on a complicated system to generate laser beams in a broad, higher-wavelength spectrum (argon to CO 2 or Ho:YAG), which is mainly absorbed by haemoglobin. Laser atherectomy at this wavelength was accomplished through direct action or by heating a metallic tip to induce vaporisation of the tissue.…”