A Secondary Circulatory system: Post a cardiovascular event

Cardiovascular diseases, specifically coronary artery disease (CAD) are the leading cause of death in first world countries. Typical surgical treatment for this is angioplasty and coronary artery bypass graft (CABG). Angioplasty refers to the opening or widening of the blocked or narrow artery to improve blood flow, usually followed by a stent placement to keep the artery from collapsing. (John Hopkins University, 2024). A CABG is taking a healthy artery/ vein from elsewhere in the body and attaching the new artery/vein in the heart near the blockage to bypass the blockade, for restored blood flow (John Hopkins University, 2024).  

Although such procedures may be required soon after a cardiac emergency, the body does have its own way of restoring its own blood flow. This phenomenon is known as coronary collateral circulation. This is described as an alternative source blood supply to an area of ischemia. This has also been shown to occur in areas of smaller infarcts or ventricular aneurysm formation, that is the body creates collateral arteries leading to improved ventricular function, therefore fewer cardiac events and improved survival. (Seiler, 2003) This process occurs through angiogenesis and arteriogenesis. These new blood vessels develop from a pre-existing plexus by sprouting. Endothelial cells, pericytes (capillaries) and smooth muscle cells are required for the maturation of the vessels, specifically larger vessels. This is not only used for the creation of new vessel growth but also in simple tissue repair and regeneration, like wound healing. Upon injury to the blood vessel, inflammatory mediations and growth factors are released leading to vasodilation (Seiler, 2003). This leads to a positive feedback loop, enhancing vascular permeability and increased numbers of monocytes and macrophages (Seiler, 2003). These inflammatory mediators also release metalloproteinases to dissolve the surrounding injury and the basal membrane of the previous vessel (Seiler, 2003). The lack of oxygen sensitizes the endothelial cells to upregulate various growth factors. These endothelial cells attach to the neighboring vessels, migrate, proliferate, thus creating a new vessel in the lumen (Seiler, 2003). Post an ischemia event, arteriogenesis becomes visible within two weeks.

Preventing CAD and therefore a cardiovascular emergency is crucial and straightforward. Exercise has also been shown to help in the development of arteriogenesis. The shear forces at the vessel wall in response to increased blood flow lead to collateral connections (Seiler, 2003). Pressure from inside the blood vessels augments substantially in response to endurance exercise training (Seiler, 2003). Therefore, let’s prevent CAD by exercising and staying healthy!