HISTOLOGIC ANALYSIS OF TRANSMYOCARDIAL CHANNELS - COMPARISON OF CO2 AND HOLMIUM-YAG LASERS

Background. Transmyocardial laser revascularization using different la sers is being tested in the treatment of refractory angina. We conduct ed comparative analysis of the acute and chronic myocardial effects of these different lasers.Methods. Transmyocardial channels were made in normal dog hearts with either a holmium:yttrium-aluminum garnet or a CO2 laser. Channels were examined histologically 6 to 24 hours, 2 to 3 weeks, and 6 weeks after creation. Results. Regardless of the laser s ource, the channels were occluded by thrombus within 6 to 24 hours. Su bsequently, organization and neovascularization of the channel region occurred. Thermoacoustic damage was initially greater with the holmium :yttrium-aluminum garnet laser, but the channel appearances were indis tinguishable from those made with the CO2 laser by 6 weeks. Conclusion s. Histologically, the myocardial effects of the CO2 and holmium:yttri um-aluminum garnet lasers are similar and differ predominantly in the amount of acute thermoacoustic injury. Channels are rapidly occluded b y thrombus and are replaced by neovascularized collagen. This suggests that the physiologic effects of these two lasers may be similar and t hat mechanisms other than blood flow through chronic patent channels s hould be considered as contributing to the clinical benefits observed with this procedure. (C) 1997 by The Society of Thoracic Surgeons.