Angiogenic response induced by mechanical transmyocardial revascularization

Abstract

Background: Angiogenesis is the proposed mechanism of transmyocardial revascularization. We evaluated mechanical transmyocardial revascularization in a chronically ischemic porcine model by measuring myocardial angiogenic response. Methods: Ameroid constrictors were implanted 6 weeks before mechanical transmyocardial revascularization. Group I (n = 5) and group II (n = 3) animals received 30 punctures with an 18-gauge needle and samples were harvested at 1 and 4 weeks, respectively, after the operation. Group III (n = 5) had sternotomy only and served as the control group. Myocardial samples were immunohistochemically stained for vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and transforming growth factor β (TGF-β) using specific antibodies. Growth factor expression was quantified by means of computer-assisted morphometry. Vascular density was assessed by immunohistochemical stain for VEGF and factor VIII. Results: Compared with group III, increased angiogenic factor levels were found in group I (VEGF 0.47 ± 0.03 mm2 vs 0.05 ± 0.05 mm2, P = .000; bFGF 0.67 ± 0.14 mm2 vs 0.03 ± 0.03 mm2, P = .000; TGF-β 1.40 ± 0.18 mm2 vs 0.09 ± 0.06 mm2, P = 0.000), and in group II (VEGF 0.34 ± 0.06 mm2 vs 0.05 ± 0.05 mm2, P = .003; bFGF 0.06 ± 0.02 mm2 vs 0.03 ± 0.03 mm2, P = .135; TGF-β 0.28 ± 0.09 mm2 vs 0.09 ± 0.06 mm2, P = .042). Vascular densities after mechanical transmyocardial revascularization were also increased (group I, VEGF stain 8.1 ± 0.6 vs 1.1 ± 0.5, P = .000; factor VIII stain 5.1 ± 2.7 vs 0.4 ± 0.3, P = .018; group II, VEGF stain 1.9 ± 0.5 vs 1.1 ± 0.5, P = 0.107; factor VIII stain 2.3 ± 0.4 vs 0.4 ± 0.3, P = .004). Conclusions: Mechanical transmyocardial revascularization is associated with increased angiogenic factor expression and concomitant neovascularization at up to 4 weeks. These changes are indistinguishable from those of laser transmyocardial revascularization. Myocardial perfusion studies are needed to establish the functional significance of these angiogenic changes. (J Thorac Cardiovasc Surg 1999; 118:849-56)