Optimizing strategies for laser angioplasty.

The intrinsic optical properties of normal and diseased vascular tissues and their interaction with continuous wave (cw) and pulsed laser light were investigated to determine the optimal source for laser angioplasty. Both intima and atheromatous plaque demonstrated increasing spectral absorbance at shorter wavelengths (in the near ultraviolet). The relative differences in absorbance between diseased and nondiseased tissues were not sufficient to allow selective ablation of plaque. Atheromatous plaque appears more resistant than normal intima to damage by cw argon laser. The interaction of tissue with a high-power, pulsed ultraviolet laser showed a nonlinear response as pulse repetition rate and pulse energy were varied. From theoretical considerations and our experimental results, we propose that a pulsed ultraviolet laser with 50 millijoules of power per pulse and a repetition rate of 10 pps would be safer and more effective for recanalization than the cw argon laser.