Here's the wiki on this topic http://en.wikipedia.org/wiki/Angiogenesis
Sounds like NO supplements help out with vascularity. AAS increase this also by boosting "VEGF" a hormone in control of vascular genesis. From this study, sounds like high cholesterol, smoking, diabetes and stress can inhibit this process.
http://circ.ahajournals.org/content/105/18/2133.full
To conclude, the study by Matsunaga et al provides more evidence that nitric oxide plays a critical role in angiogenesis. Certainly, VEGF can enhance endothelial regeneration, restore endothelial function, and stimulate angiogenesis. Aggressive treatment of comorbid conditions (eg, hypercholesterolemia, hypertension, diabetes, and tobacco exposure) to restore endothelial function, however, may be just as important as the administration of gene therapies or recombinant angiogenic proteins in the success of therapeutic angiogenesis.
http://www.angio.org/understanding/growth.php
Above is a list of angiogensis inhibitors, maybe you are taking something on this list? Also notice HCG is on the list.
http://www.ncbi.nlm.nih.gov/pubmed/12514108
Marijuana is also an angiogenesis inhibitor if that's something you do