Laser thrombolysis is a procedure for removing blood clots in occluded arteries using pulsed laser energy. Removing thrombus with microsecond laser pulses has emerged as a promising method for the treatment of acute myocardial infarction and stroke. Safety and selectivity are achieved by selective absorption of light by the clot and not by the vessel. During the procedure, two delivery methods, contact and non-contact, can be used to delivery laser pulses into arteries through a fiberoptic catheter. No detailed study has compared the effects of these two modalities on the ablation efficacy.
In this study, we measured the ablation efficacy of porcine clots at 577nm with one microsecond laser pulses. The clot sample was confined in a 3mm tube as a vessel model. The laser pulses of 10-75mJ were delivered via flushing catheters. The catheter consisted of a quartz fiber (200-400mm core diameter) contained inside of a 1mm flexible Teflon tube. Distilled water or saline were injected with a syringe infusion pump at a flow rate 4mL per minute through the tube to wash away the removed clot or gel around the target site. Cavitation bubble formation and acoustic pressure were also visualized and measured on gelatin-based thrombus models for understanding the ablation mechanism.
Conclusions: 1) Contact ablation was more efficient than the non-contact ablation (>3 times). 2) The ablation efficacy is independent of the fiber size for both contact and non-contact delivery. 3) The bubble size are smaller for contact vs. non-contact (up to 25%), whereas the differences in acoustic pressure are not significant (<15%). 4) The confined boundary effect for the contact ablation may account the difference in the laser energy needed to removed similar amount of the thrombus. 5) The differences in the laser energy and the fiber size may benefit the clinical use of laser thrombolysis.
H. Shangguan, L. W. Casperson, and S. A. Prahl. Effects of Laser Delivery on Ablation Efficacy of Thrombus in Liquids: In Vitro Study. Lasers in Surgery and Medicine, April 3-6, Phoenix, AZ, 1997.