Are there vascular density gradients along myocardial laser channels?

Background. Clinical studies suggest that transmyocardial laser revascularization may improve regional blood flow of the subendocardial layer. The vascular growth pattern of laser channels was analyzed. Methods. Twenty pigs were randomized to undergo ligation of left marginal arteries (n = 5), to undergo transmyocardial laser revascularization of the left lateral wall (n = 5), to undergo both procedures (n = 5) or to a control group (n = 5). All the animals were sacrificed after 1 month. Computed morphometric analysis of vascular density of the involved area was expressed as number of vascular structures per square millimeter (±1 standard deviation). Results. The vascular density of the scar tissue of the laser channel was significantly increased in comparison with myocardial infarction alone: 49.6 ± 12.8/mm2 versus 25.5 ± 8.6/mm2 (p< 0.0001). The vascular densities of subendocardial and subepicardial channel areas were similar: 52.9 ± 16.8/mm2 versus 46.3 ± 13.6/mm2 (p = 0.41). The area immediately adjacent to the channels showed a vascular density similar to that of normal tissue: 6.02 ± 1.7/mm2 versus 5.2 ± 1.9/mm2 (p = 0.08). In the infarction + transmyocardial laser revascularization group, the channels were indistinguishable from infarction scar. Conclusions. Scars of transmyocardial laser revascularization channels exhibit an increased vascular density in comparison with scar tissue of myocardial infarction, which does not extend into their immediate vicinity. There was no vascular density gradient along the longitudinal axis of the channels.