The Laser Hot Balloon Catheter:
a New Approach to Treating Atheromatous Lesions
Tsunenori Arai
This chapter describes a new type of thermal balloon angioplasty. Our laser hot balloon (LHB) catheter is characterized by short-duration heating (<10 s) with uniform temperature distribution throughout the balloon. We have also successfully developed independent control of balloon temperature and the heating duration. We used the new technique to study the optimum combi- nation of balloon temperature and heating duration to suppress restenosis after percutaneous transluminal coronary angioplasty (PTCA).
PTCA has been the gold standard treatment for ischemic heart diseases, in particular for acute myocardial infarction and angina. Restenosis in the chronic phase after PTCA has been the most serious issue to date, with approximately 30%–40% of patients suffering another heart attack due to restenosis in the treated vessel. Hot balloon angioplasty involves softening the vessel wall to obtain sufficient dilatation by temperature elevation and the addition of localized thermal coagulation to suppress granulation tissue growth in the vessel. Using a radio-frequency (RF) hot balloon, sufficient expansion of the lumen at low dilatation pressure has been demonstrated;
however, the problem of restenosis after PTCA has not been solved. The RF balloon requires 1 min to reach 60°C, allowing thermal injury to spread around the vessel and over the vessel wall.
We developed the new LHB catheter with a balloon 3 mm in diameter and 20mm in length. One lumen of the LHB catheter is used for guidewire inser- tion and the other two for contrast medium irrigation with a thin silica fiber installed in one of the irrigation lumens, and a thin thermocouple in the other.
The continuous-wave-diode laser beam is focused into the silica fiber, and a metal mesh tube is located at the tip of the fiber, which is connected to the
33 Faculty of Science and Technology, Department of Applied Physics and Physico- Informatics, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan
irrigation lumen and placed into the balloon. The laser beam emerges from the tip of the fiber and is reflected many times in the metal mesh tube, converting the light to heat energy. This heat is transferred to the contrast medium, which is irrigated into the lumen. The heated contrast medium flows through the balloon to obtain a uniform temperature distribution and the contrast medium temperature in the balloon is measured with the thermocouple.
34 T. Arai
