ND-YAG LASER PHOTOCOAGULATION OF CANINE MYOCARDIUM WITH THE TRANSPARENT CONTACT PROBE

Laser photocoagulation of myocardium is an alternative to surgical resection in the treatment of drug resistant ventricular tachycardia. In certain areas, of the heart, however, bare fibre delivery of laser energy involves a risk of unintentional damage to nearby structures. The purpose of the study was to determine whether Nd-YAG laser irradiation, delivered with the transparent contact probe, would produce adequate laser photocoagulation of the canine myocardium in comparison to bare fibre delivery of the laser energy. In nine mongrel dogs, continuous wave Nd-YAG laser irradiation with and without a transparent contact probe was directed at the epicardium. Pulse power was 10, 15 and 20 W, pulse duration 5, 7 and 10 s, and spot size was 1 mm. A total of 178 lesions were analyzed microscopically. After a 200 J pulse energy delivered by the contact probe, the lesion depth was 4.9±0.5 mm (mean±s.d.), which is usually adequate to ablate arrhythmia sites. Bare fibre delivery of laser energy did not produce deeper lesions. There was no difference between the bare fibre and the transparent probe in the occurrence of major arrhythmias (4/86 bare fibre, 3/92 transparent probe). We conclude that the transparent contact probe allows safe and effective laser irradiation of sites of origin of ventricular arrhythmias. © 1992 Baillière Tindall.