Blood Clots

What causes blood clots?

Blood clots form when there is damage to the lining of a blood vessel, either an artery or a vein. The damage may be obvious, such as a laceration, or may occur on the microscopic level. As well, blood will begin to clot if it stops moving and becomes stagnant.

Venous thrombosis or blood clots in a vein occur when a person becomes immobilized and muscles are not contracting to push blood back to the heart. This stagnant blood begins to form small clots along the walls of the vein. This initial clot can gradually grow to partially or completely occlude or block the vein and prevent blood from returning to the heart. An analogy to this process is a slow moving river. Over time, weeds and algae start to accumulate along the banks of the river where the water flows more slowly. Gradually, as the weeds start to grow, they begin to invade the center of the river because they can withstand the pressure of the oncoming water flow.

Arterial thrombi (blood clots in an artery) occur by a different mechanism. For those with atherosclerotic disease, plaque deposits form along the lining of the artery and grow to cause narrowing of the vessel. This is the disease process that may causeheart attack, stroke, or peripheral artery disease. If a plaque ruptures, a blood clot can form at the site of that rupture and can completely or partially occlude the blood flow at that point.

Reviewed on 7/10/2014

STAY INFORMED

Get the Latest health and medical information delivered direct to your inbox!