Effects of Nd:YAG laser coagulation of myocardium on coronary vessels

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Abstract
Laser coagulation of arrhythmogenic myocardium proved to be an effective surgical therapy for refractory arrhythmias. To determine the influence of NdYAG laser coagulation of myocardium on coronary vessels, a total of 48 transcatheter laser impacts (10 W, 10 sec, 7 W mm2) were directed to the left ventricular free wall via endocardial (24 lesions in 2 dogs) or epicardial (24 lesions in 2 dogs) approach. In 8 of 24 endomyocardial lesions (2 and 6 months old) coronary vessels with a diameter of > 50 μm were found within the coagulation zones. The volume of these lesions was significantly (P < 0.0l) smaller (139 ± 43 mm3) than those (n = 16) with coronary vessels measuring 3). Volumes of epimyocardial lesions (1‐2 hours old) produced by transcoronary irradiation with normal coronary blood flow were significantly (P < 0.01) smaller (31 ± 17 mm3) than with reduced (73 ± 22) or interrupted (119 ± 34 mm3) blood flow (n = 8, each). Both directly irradiated coronary vessels and those found within the coagulation zones and scars appeared histologically normal through all layers with an intact intima without fibrosis or thrombosis. The ultrastructure of irradiated arteries, even with total interruption of blood flow, was no different from that of non‐irradiated controls. Thus, coronary artery blood flow significantly reduces the volume of coagulated myocardium, whereas the vessels themselves appear to remain undamaged by laser irradiation as used for myocardial coagulation.