PHYSIOLOGY, HISTOLOGY, AND 2-WEEK MORPHOLOGY OF ACUTE TRANSMYOCARDIALCHANNELS MADE WITH A CO2-LASER

Background. Transmyocardial revascularization with a CO2 laser appears to improve symptoms in patients with refractory angina. However, it r emains controversial as to whether blood flow through the channels is the mechanism of benefit, especially in the acute setting. Methods and Results. Three protocols were used to test whether blood flows throug h transmyocardial CO2 laser revascularization channels. First, channel s were made in excised, cross-perfused dog hearts (n = 5) using a CO2 laser (The Heart Laser; PLC Systems Inc, Milford, MA; 40 J/pulse) foll owed by ligation of the proximal left anterior descending coronary art ery. Colored microspheres injected into the left ventricular chamber f ailed to detect any significant transmyocardial blood flow. In the sec ond protocol (n = 4), laser channels were created in the left anterior descending artery territory, the left anterior descending artery was ligated, and the hearts were excised after 24 hours. Triphenyltetrazol ium chloride staining revealed that no viable myocardium was detected around the laser channels in the ischemic myocardium. Finally, channel s examined 2 weeks after creation in normal (n = 6) or ischemic (n = 4 ) myocardium did not maintain their original caliber but were invaded by granulation tissue, which included a large amount of smaller vascul ar spaces and vessels of various sizes. Conclusions. Transmyocardial l aser revascularization channels made with this CO2 laser did not provi de acute myocardial perfusion or preserve myocardial viability in the face of acute ischemia. Channel morphology changes dramatically within the first 2 weeks. To the degree that these findings pertain to human myocardium, the results suggest that transmyocardial blood flow may n ot be the mechanism of benefit of this procedure, particularly in the acute setting. (C) 1997 by The Society of Thoracic Surgeons.