Percutaneous Nd:YAG laser coagulation of ventricular myocardium in dogs using a special electrode laser catheter.

A novel catheter system was used for intracardiac electrogram recordings, ventricular pacing and continuous-wave Nd:YAG laser (1,064 nm) irradiation of ventricular myocardium in eight dogs. Radiation at a power of 10 W for 3, 5, and 10 seconds was delivered through a 400 microns optical fiber. Power density was 15 W/mm2. A total of 96 laser injuries (12 per dog) were produced in selected sites in both the right and the left normal canine ventricle. Ventricular arrhythmias were noted during 12 of 96 (12.5%) laser pulses. Programmed electrical stimulation performed during control study immediately (all dogs) at 2 days (two dogs), and 4 months (4 dogs) following the experiments showed no episodes of sustained or nonsustained ventricular tachycardia. Radiation energies up to 50 J (10 W over 5 s) caused focal injuries of homogeneous coagulation/fibrosis localized to the target area, without vaporizing tissue and forming craters. Morphometrically and histologically there was a direct relationship between the energy of radiation delivered, and the extent and severity of the injury produced. The maximum size of lesions measured 7/11 mm (diameter/depth). Using a special catheter system laser coagulation of myocardium can be accomplished percutaneously. This method can create controlled subendocardial injuries without major side effects and appears to overcome most disadvantages of transcatheter high energy direct-current shocks when used as a regular course of procedure in ablation of arrhythmogenic tissue in the heart.