Angiogenesis is the formation of new blood vessels due to the development of existing capillaries and postcapillary veins. The first vessels in the developing embryo form through vasculogenesis, after which angiogenesis is responsible for most, if not all, blood vessel growth during development and in disease.

In normal adult coronary arteries, endothelial and vascular smooth muscle cells are nondividing tissue. However, during growth and development and under conditions of ischaemia, hypoxia, inflammation or other stresses, these cells start to migrate and divide. Blood vessel formation passes through several steps, including: the dissolution of the bond between the endothelium and the underlying basement membrane, migration, adhesion and reattachment of the endothelial cells, proliferation and tube formation. Cellular and molecular changes are required for this process, which is complex and as yet poorly understood.