Pathological analysis of transmyocardial laser revascularization for acute myocardial ischemia

Transmyocardial laser revascularization (TMLR) is an alternative surgical procedure for the patients with intractable coronary artery disease. Efficacy of the treatment has been established, however, the mechanism of TMLR is still controversial. In this study, we investigated the effect of TMLR on acute myocardial ischemia with pathological analysis. Under general anesthesia, the hearts of mongrel dogs were exposed. Then, the anterior descending branch of the left coronary artery was ligated to make the ischemic area on the left ventricle. Laser punctures were made 30 minutes after coronary ligation in the TMLR group (n = 5), and no further procedure was performed after coronary ligation in the AMI group (n = 5). One month after these operations, the hearts were extirpated for pathological studies. The avascular area and the viable area in the infarcted area were macroscopically separated by Evans blue dye and triphenyltetrazolium chloride (TTC) staining. Thickness of the left ventricular wall in the infarcted area was also measured and compared. Furthermore, all of the infarcted area and the lased area were microscopically examined with Masson's trichrome stain. The size of the infarcted area in the TMLR group was smaller than that in the AMI group. It was significantly different (p < 0.05) in the basal and apical regions. As a result, the ratio of the viable area by the avascular area was larger in the TMLR group than in the AMI group. It was significantly different (p < 0.05) in the apical region. In the basal region, the thickness of the left ventricle in the AMI group was thinner than that of untreated dogs (normal group: n = 5), and there was no difference between the normal group and the TMLR group. Whereas in the apical region, significant difference of the thickness was found among AMI, TMLR, and normal groups (p < 0.05). In conclusion, our study supported; 1) TMLR reduced overall infarcted size, and increased the viable area in the infarcted area, 2) TMLR prevented the thinning of the left ventricular wall.