Does laser injury induce a different neovascularisation pattern from mechanical or ischaemic injuries?

Aim: To analyse the arteriolar pattern of laser induced channels and their surroundings compared with mechanical and ischaemic injury.

Methods: 24 pigs were randomised to a myocardial infarction group, a transmyocardial laser revascularisation group, a needle group, or a control group. In the laser revascularisation and needle groups, five channels were created either with a 1.75 mm probe holmium-YAG laser or a Tru-cut needle of the same size. Animals were killed 28 days later. Morphometric analysis of vascular density was expressed as the mean (SD) number of arteriolar structures/cm(2).

Results: Laser and needle channels were completely invaded by granulation tissue. Their surface areas did not differ significantly: 2.28 (0.7) mm(2) and 2.38 (1.1) mm(2), respectively (p = 0.82). Within both types of channel, arteriolar density was significantly increased in comparison with the myocardial infarction scar: 197 (52)/cm(2) and 190 (64)/cm(2), respectively (p = 0.8) versus 56 (20)/cm(2) (p < 0.001 for both comparisons). The area of 1 mm width immediately adjacent to the laser and needle channels showed a density of 25 (16)/cm(2) and 23 (18)/cm(2), respectively, which is similar to that of normal tissue (28 (10)/cm(2); p = 0.6 and p = 0.4, respectively). The mean arteriolar diameter was similar throughout all the regions analysed.

Conclusions: Both laser and needle channels produce a similar increase in arteriolar structures, which is limited to the lesion itself. This suggests that laser injury is not more potent as an angiogenic stimulator than mechanical injury, which in turn is superior to infarction.