Anatomy of … Clots

When a person has a cut or injury that results in bleeding, the bleeding stops because blood coagulates – it forms a clot of blood cells and fibrin strands. If blood didn't clot, even minor cuts could become serious medical issues. Clots are necessary, but clots can also cause damage. A clot that forms in a blood vessel or in the heart can cause damage or even death. The medical term for a clot is a thrombus. A thrombus that forms in a blood vessel and travels to another part of the body is called an embolus. If a thrombus or embolus blocks the healthy flow of blood and oxygen, it can be life-threatening and cause a heart attack, stroke, damage to other vital organs (such as kidneys and lungs), or injury to limbs. For example, a thrombus that develops in a leg vein can float with blood flow through the veins and the heart into the lungs, causing a more serious complication called pulmonary embolism.

A thrombus can develop in the arterial system where blood with oxygen is pumped under high pressure from the heart to all of the organs and tissues in the body. More commonly, thrombi develop in the venous system where blood is flowing slowly from the organs back to the heart and lungs. Risk factors for development of thrombi in the arteries include atherosclerosis, immune disease such as lupus, genetic disorders such as sickle cell anemia, and trauma. Risk factors for development of thrombi in veins include physical inactivity (especially prolonged bed rest due to sickness or disability), smoking, pregnancy, varicose veins, obesity, trauma, and genetic or autoimmune diseases.

The risks and causes of thrombi include atherosclerosis (plaque build-up on the veins), injury or trauma to the blood vessel due to accident, surgery, fracture, burn, varicose veins or other vascular diseases, pregnancy, contraceptive use, high blood pressure, bed rest or long periods of inactivity, tobacco use, being overweight, and lack of exercise.

Surgery is also a risk factor for development of venous thrombi. If you're scheduled for surgery, discuss your risks for thrombi with your surgeon, who may prescribe medication to help prevent blood clots or recommend pre-surgical exercise. Be up and about as soon as possible after your surgery. If surgery isn't in your future, the best way to prevent thrombi – and you've heard this before – is to not use tobacco products, maintain a healthy weight, and get regular exercise.