Liquid Core Light Guide for Laser Angioplasty

INTRODUCTION ECHNICAL demands for laser angioplasty catheters, T particularly for destinations in coronary arteries are in general, more stringent than those for angiography and balloon angioplasty . Catheters for laser angioplasty must be flexible and atraumatic in order to safely negotiate the angles of curvature encountered within tortuous and stenotic vascular lumens while being rugged, mechanically and optically. Optimally, laser catheters would be compatible with conventional catheterization and guidewire techniques to guide them to distal vessels via manipulation from percutaneous sites. Once maneuvered to the desired irradiation site, precise laser energy exposure to the pathologic tissues is required without interference from blood or ablated debris. An adequate volume of tissue must be removed to make the procedure worthwhile while incurring minimal damage to surrounding structures. Thrombosis, vasospasm, or perforation of the vessels must be avoided, while providing a favorable substrate for vascular healing. Thus far, catheter designers have utilized fused silica fibers to transmit the laser energy. While integrating these fused silica fibers into catheters is possible, it can be complex, expensive, and sometimes limited by stiffness imposed by the silica fibers. We sought to find a simple, inexpensive alternative to fused silica fibers which might provide superior catheter characteristics. Optically-transparent fluid was studied as a means of transmitting energy in a laser angioplasty catheter and the performance of a fluid-core catheter for removing coronary artery obstructions was evaluated. Fluid-core optical transmission devices have been used primarily for industrial applications where flexibility, cost, and high optical throughput are considerations. Medical applications of these devices have been scant. In one report, Sander describes guiding Nd : YAG laser energy through a stream of water utilizing the difference in indexes of refraction between water and air to carry infrared light short distances from fiber tips to treat tumors in the rectum and stomach [4].