SIMULATION OF HEAT-GENERATION FOR TRANSCATHETER ND-YAG LASER PHOTOCOAGULATION OF MYOCARDIUM

Nd-YAG laser photocoagulation is a successful technique for the intrao perative treatment of arrhythmia. Experimental endocardial transcathet er laser application, however, occasionally causes tissue vaporization and perforation. Intramural heat generation was simulated in a Monte Carlo model as a function of laser beam profile and divergence versus individually varying tissue properties. Heat generation at the tissue surface was dominated both by the beam profile and the individual tiss ue properties. High beam divergence may help to reduce heat accumulati on in subsurface regions. Heat distribution in depth as well as backsc attering are not substantially influenced by beam parameters but are m ainly determined by the optical tissue properties. Surface cooling can help to avoid overheating. A catheter concept for safe endocardial ph otocoagulation is presented including a highly divergent beam of maxim ized spot size, an effective catheter flushing, and shielding of blood .