Experimental angioplasty: circumferential distribution of laser thermal energy with a laser probe.

A new laser probe that converts argon laser energy to heat in a metallic cap on a fiberoptic fiber was compared with a bare argon laser fiberoptic catheter system for the dissolution of atherosclerotic obstructions under fluoroscopic guidance in 24 atherosclerotic rabbits. Twelve animals were randomly assigned to receive treatment with either a bare fiberoptic system or a laser probe coupled to an argon laser. Both fibers had similar outer (0.9 mm) and core (400 mu) diameters. Pulses of 1 watt for 1 second's duration were delivered from the tip of the fiberoptic system, while pulses of 6 watts for 2 seconds' duration were delivered to the laser probe. The results of angiography indicated that widening of luminal stenosis was seen in only 2 of 12 animals treated with the fiberoptic system compared with 8 of 12 animals treated with the laser probe. Perforation of the vessel wall occurred more frequently with the fiberoptic fiber (9 of 12 animals) as compared with the laser probe (1 of 12 animals). Histologic examination of direct laser radiation with the fiberoptic fiber revealed a small localized laser defect along one side of the vessel wall associated with charring, a gradient of thermal injury and considerable thrombus formation. In contrast, those vessels treated with the laser probe showed histologic evidence of thermal injury distributed evenly around the entire luminal circumference. This was associated with minimal charring, a gradient of thermal injury and thinner, flatter thrombus formation. Carbonization of the metallic tip and adherence of atherosclerotic debris with secondary vessel tearing were potential adverse effects of the laser probe.(ABSTRACT TRUNCATED AT 250 WORDS)