LASER-MEDIATED TRANSMURAL MYOCARDIAL CHANNELS DO NOT SALVAGE ACUTELY ISCHEMIC MYOCARDIUM

Objectives. We sought to determine whether the presence of transmural laser-made channels could provide blood flow to ischemic myocardium. Background. Laser-made transmural channels have been used in patients to restore blood flow to ischemic myocardium. Whether such channels actually relieve ischemia is unclear. We therefore tested the concept in an animal model of acute ischemia. Methods. Eighteen dogs underwent 6 h of permanent coronary artery occlusion. At 30 min after occlusion, 8 dogs were randomized to the laser-treated group (30 to 40 transmural channels, 1 mm in diameter, were made in the cyanotic area using a holmium: yttrium-aluminum-garnet laser), and 10 were randomized to the control group (no treatment). Transmural blood flow was measured before and after treatment using radiolabeled microspheres. Regional segment shortening and myocardial lactate content were measured in four of the control and two of the laser-treated dogs. Infarct size was measured in all animals using triphenyltetrazolium chloride staining. Results. Laser channels failed to increase blood flow to ischemic tissue. After laser channels were made, mean transmural flow averaged 0.10 +/- 0.03 versus 0.11 +/- 0.03 ml/min per g in treated versus control dogs, respectively. Furthermore, infarct size was similar in both groups (46 +/- 6% vs. 43 +/- 7%, respectively, of the myocardium at risk, p = NS). In addition, the presence of laser channels neither improved regional myocardial function nor enhanced washout of accumulated lactate. Conclusions. Direct laser revascularization of the heart did not provide any immediate benefit to ischemic myocardium in this canine model of coronary artery occlusion. Thus, it is doubtful that direct laser-mediated myocardial revascularization would be of immediate benefit in the treatment of patients with acute ischemia.