IN-VIVO TEMPERATURE-MEASUREMENT DURING TRANSCATHETER ENDOMYOCARDIAL ND-YAG LASER IRRADIATION IN DOGS

Intramural temperatures were monitored during catheter-directed endomy ocardial non-contact laser irradiation by means of an array of thermoc ouples inserted epicardially. Via a novel electrode-laser catheter, a total of 30 Nd-YAG laser pulses, 1064 nm, 25 W/15 s, 20 W/30 s, 15 W/4 5 s, n = 10 each, were aimed at various endocardial sites in the ventr icles of four dogs. Temperatures increased gradually after the onset o f the laser pulses. Maximum values were measured in the central area o f the irradiated spots: 100 +/- 15 degrees C at 25 W, 78 +/- 23 degree s C at 20 W and 80 +/- 13 degrees C at 15 W. Application of 300 J of l aser energy induced significantly higher temperatures at 25 W (p < 0.0 2) than at 20 or 15 W (20 vs 15 W: p > 0.05), Initial temperature rise and lesion formation was accompanied by dwindling of local electrical potentials. There was no crater formation. Transcatheter non-contact Nd-YAG laser coagulation of healthy ventricular myocardium can be perf ormed in a safe and controllable manner at power settings up to 20 W a nd laser energies up to 675J.