Venous Thrombosis

• A blood clot that forms in a vein is called venous thrombosis. This type of clot, caused by immobilization, such as that which often results from surgery and pregnancy, prevents the muscles from contracting and pushing blood through the veins back to the heart.
  
  

Arterial Thrombi

• Arterial thrombi are caused when blood clots form in the arteries.They are caused by the buildup of plaque. The risk of heart attack, stroke and peripheral artery disease is associated with arterial thrombi.
  
  

Blood Clots in the Heart

• Blood clots can also form in the heart when it does not beat properly. Blood may become stagnant along the heart's wall and form clots. This condition is often seen after a heart attack.
  
  

Risks

• There are several risk factors that can increase the likelihood of blood clots. These include high blood pressure, high cholesterol, diabetes, smoking and a family history of blood clots.
  
  

Symptoms

• Symptoms to look for, especially in the arms, legs, or feet, include swelling, redness, tenderness or pain over a vein, a sharp pain in the area, dilation of a vein and a dull aching pain.
  
  

Danger

• When blood clots break away or block blood flow, they can pose immediate danger and may become fatal. If chest pain, bloody spit or breathlessness occurs, seek immediate help.