Differential photoabsorption using argon laser radiation on atherosclerotic plaque in non-hemolyzed and hemolyzed blood.

Since argon laser radiation (488 to 514 nm) can vaporize human atherosclerotic plaque, we determined whether different blood media--hemolyzed versus non-hemolyzed blood--can alter photoabsorption of atherosclerotic plaque. Forty cadaveric aortic fibrous plaque samples were fitted onto small vials containing 0.02 ml of either non-hemolyzed blood or hemolyzed blood over the surface of the plaque. The distal end of a 400-mu core diameter quartz fiber was directed onto the surface of the plaque and the proximal end of the fiber was connected to an argon laser. The vaporized area and depth of plaque penetration were measured and the estimated volume of crater formation was derived. Following 2.5, 5, 10 and 20 J of laser energies, vaporized volumes were 0.12, 0.72, 0.97 and 4.09 mm3, respectively, for hemolyzed blood and were 0 (p less than 0.01), 0 (p less than 0.01), 0.92 (NS) and 4.39 mm3 (NS), respectively, for non-hemolyzed blood. Laser radiation destroys red blood cells; the higher the energies, the greater the hemolysis. Thus, different blood media such as hemolyzed and non-hemolyzed blood can alter photoabsorption of atherosclerotic plaque. Low level argon laser absorption upon plaque can occur under hemolyzed blood but not under non-hemolyzed blood. Since higher levels of argon laser energies cause greater lysis of red blood cells, comparable degrees of plaque ablation are observed under either blood medium.