Objective: The effect of enoxaparin and fibroblast growth factor-1 (FGF-1) on post-infarction capillary density and regional myocardial blood flow (RMBF) was examined. Methods: New Zealand White rabbits received an intramyocardial injection of either physiological saline, FGF-1 + enoxaparin, FGF-1 or enoxaparin directly after ligation of the left anterior descending artery. RMBF and capillary density were investigated using fluorescent microspheres and histological examination. Results: One week after infarction a significant difference in the number of capillaries could be demonstrated within the FGF-1 + enoxaparin group (p < 0.001 versus the control group), the FGF-1 group (p < 0.01) and the enoxaparin group (p < 0.05). Treatment with FGF-1 + enoxaparin resulted in a significantly increased number of capillaries compared to treatment with FGF-1 (p < 0.05) and enoxaparin (p < 0.05) alone. Additionally, all groups treated with FGF-1 and/or enoxaparin showed a significant increase of microvessel density in the treated ischemic border zone compared to the non-treated ischemic border zone (p < 0.001 for FGF-1 + enoxaparin, p < 0.01 for FGF-1, p < 0.05 for enoxaparin). RMBF was significantly increased within the FGF-1 + enoxaparin group compared to the control group (p < 0.05). Moreover, perfusion rates within the FGF-1 + enoxaparin-treated area did not significantly differ from the pre-infarction values. Conclusion: Treatment with either enoxaparin or FGF-1 or FGF-1 + enoxaparin resulted in increased microvessel growth. However, only the combination of enoxaparin with FGF-1 promotes capillary growth and RMBF. Thus, we conclude that enoxaparin enhances the angiogenic potential of intramyocardially injected FGF-1 in the acutely infarcted rabbit heart. Copyright (c) 2005 S. Karger AG, Basel.