Local Extravascular Growth Factor Delivery in Myocardial Ischemia

A number of angiogenic growth factors have been demonstrated in vivo to promote angiogenesis in ischemic myocardium, including basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF). We used the porcine ameroid constrictor model to simulate chronic ischemia in an effort to study the role of exogenous growth factor delivery in the development of coronary collateral circulation. Heparin alginate microspheres were used to deliver bFGF, while an implantable osmotic pump was used for VEGF delivery. Anti-von Willebrand antibody staining was used to visualize microvessels in the porcine heart sections obtained from both ischemic and non-ischemic myocardium. A significant increase in the number of microvessels in growth factor-treated pigs compared to control animals was noted. Myocardial blood flow was used to determine the physiologic impact of these findings. In bFGF and VEGF treated animals resting collateral flow values significantly exceeded those of the control group. In addition, both bFGF and VEGF administration resulted in improvements in myocardial perfusion sufficient to prevent stress-induced deterioration of myocardial performance. Results of the studies demonstrate that local perivascular drug delivery can be effectively used to induce angiogenesis in chronically ischemic myocardium.