Nd-YAG laser-induced injury in dog myocardium: optical and ultrastructural study of early lesions.

To characterize myocardial lesions induced by Nd-YAG laser in vivo, laser pulses were delivered on the epicardial surface of beating dog hearts. Acute lesions were studied at the optical and ultrastructural levels. The size of the lesions depended on the power of the laser beam. Tissue vaporization could be avoided if total delivered energy did not exceed 350 J. Laser energy induced different types of myocardial necrosis distributed in concentric layers of coagulation necrosis, and contraction band necrosis. Thus, laser energy can produce controlled irreversible lesions without crater formation. These effects may be of use in the treatment of arrhythmias.