Angiogenesis in transmyocardial revascularization: comparison of laser versus mechanical punctures

Background. Transmyocardial laser revascularization (TMLR), which has been shown to reduce angina in clinical trials, was originally based on the belief that laser channels are unique and can remain patent. An increasing body of evidence indicates otherwise, and transmyocardial revascularization (TMR) angiogenesis is currently thought to be induced by nonspecific inflammatory response to tissue injuries. We tested the hypothesis that mechanical transmyocardial revascularization (TMMR) may induce angiogenic responses similar to that seen with lasers. Methods. Ameroid constrictors were implanted around proximal circumflex arteries of porcine hearts. Six weeks later, they were randomly assigned (n = 5 each) to receive 10 transmural channels in the ischemic zone by a carbon dioxide laser (group I) or by a needle (group II). A third group (group III) had 30 needle channels in the same area, while a control group (group IV) received no TMR. The hearts were harvested 1 week later, and, using immunohistochemistry, vascular endothelial growth factor (VEGF) expression was studied and quantified by computerized morphometric analysis. Densities of vascular structures positively stained for VEGF per high-power field (HPF) were also compared. Results. Virtually no TMR channels remained patent histologically. Group III had a significant higher level of total VEGF expression (14.18 ± 0.78 mm2) compared with group I (7.07 ± 2.06 mm2, p< 0.001) and group II (4.74 ± 3.35 mm2, p< 0.001). Vascular density was significantly elevated in all treatment groups compared with the control (group I, 7.7 ± 0.8/HPF vs group II, 4.5 ± 2.3/HPF vs group III, 8.1 ± 0.6/HPF vs group IV, 1.1 ± 0.5/HPF). Conclusions. In view of the significant cost implications, our findings that needle punctures may also induce angiogenic response comparable with that with laser suggest that it is justifiable and desirable to include a TMMR arm for comparison with TMLR in future clinical trials.