Are there vascular density gradients along myocardial laser channels?

Background. Clinical studies suggest that transmyocardial laser revasculari zation may improve regional blood flow of the subendocardial layer. The vas cular growth pattern of laser channels was analyzed. Methods. Twenty pigs were randomized to undergo ligation of left marginal a rteries (n = 5), to undergo transmyocardial laser revascularization of the left lateral wall (n = 5), to undergo both procedures (n = 5) or to a contr ol group (n = 5). All the animals were sacrificed after 1 month. Computed m orphometric analysis of vascular density of the involved area was expressed as number of vascular structures per square millimeter (+/- 1 standard dev iation). Results. The vascular density of the scar tissue of the laser channel was s ignificantly increased in comparison with myocardial infarction alone: 49.6 +/- 12.8/mm(2) versus 25.5 +/- 8.6/mm(2) (p < 0.0001). The vascular densit ies of subendocardial and subepicardial channel areas were similar: 52.9 +/ - 16.8/mm(2) versus 46.3 +/- 13.6/mm(2) (p = 0.41). The area immediately ad jacent to the channels showed a vascular density similar to that of normal tissue: 6.02 +/- 1.7/mm(2) versus 5.2 +/- 1.9/mm(2) (p = 0.08). In the infa rction + transmyocardial laser revascularization group, the channels were i ndistinguishable from infarction scar. Conclusions. Scars of transmyocardial laser revascularization channels exhi bit an increased vascular density in comparison with scar tissue of myocard ial infarction, which does not extend into their immediate vicinity. There was no vascular density gradient along the longitudinal axis of the channel s. (C) 1999 by The Society of Thoracic Surgeons.