Use of the thermal laser effect of laser irradiation for cardiovascular applications exemplified by the Nd:YAG laser

Techniques of percutaneous transluminal application of laser energy for vessel recanalization have been used clinically since 1983. The commonly used Nd:YAG and argon lasers achieve ablation of atherosclerotic plaques by thermal action (vaporization). In order to reduce undesirable thermal damage in the neighborhood of the target tissue and to avoid vessel perforation, optimal irradiation parameters, modified (atraumatic) fiber tips (hot tips, sapphires), and steerable catheter systems needed to be implemented. Favorable results from peripheral application have encouraged use in the coronary circulation. More recently, coagulative tissue effects of circumferential irradiation of the vessel wall during balloon dilatation have been used for stabilization of acute and late results after mechanical balloon angioplasty. Enhancement of the differential light absorption of atherosclerotic plaque by use of biological dyes may further improve selective intravascular laser application. Intraoperative ECG-guided laser coagulation of arrhythmogenic areas of myocardium is a method for treatment of malignant arrhythmias. Transluminal non-operative application of myocardial laser photocoagulation has now been tested experimentally and shown to be safe and effective. There was no arrhythmogenicity or thermal damage of coronary arteries associated with this method. Innovative techniques such as nanosecond pulsed excimer lasers (athermal action) and development of "intelligent" lasers--which are equipped with spectroscopy-guided feedback systems for plaque recognition--have opened new perspectives and will further improve safety and efficacy of clinical laser application. However, according to current experience, the thermally acting Nd:YAG laser is an effective and versatile mode of laser therapy for selected cardiovascular indications.