Blood flows through your body as a liquid contained within arteries and veins. Under certain conditions, a jellylike blood clot forms inside these blood vessels, causing partial or complete blockage. Some clots go unnoticed, whereas others produce such symptoms as pain, color changes and swelling. The exact symptoms vary depending on whether the clot occurs in an artery, superficial vein or deep vein. Blood clots are found less commonly in the arms than in the legs. Only about 10 percent of blood clots involving deep veins -- known as deep venous thrombosis (DVT) blood clots -- occur in the arms, according to an August 2012 "Circulation" article. Recognizing the symptoms of arm blood clots will help you know when to seek medical attention.
Pain is one of the most common symptoms of a blood clot. It may be mild if the clot is small, or severe if the clot is large or located in an artery. Arterial blood clots are particularly painful because blockage of the artery reduces the delivery of oxygen to the area supplied by the artery, leading to cell malfunction and even death. Blood clots in the superficial veins -- the veins located just below the surface of the skin -- generally cause pain in the area immediately around the clot. DVT blood clots tend to cause more widespread pain, sometimes affecting much of the arm. Pain with these clots often begins as a mild discomfort, then becomes progressively more severe.
Swelling is usually most obvious with DVT blood clots. These clots generally form in the axillary and subclavian veins, which are the large veins extending from the upper arm, through the armpit and shoulder regions and into the chest. These veins are responsible for carrying most of the blood from the arm toward the heart, so when they become blocked, the blood backs up to cause prominent swelling of the hand and much of the arm. Swelling with superficial vein blood clots tends to be localized to the area around the clot. It is primarily caused by inflammation of the vein containing the clot. Swelling is uncommon with arterial blood clots, appearing only when extensive cell death occurs in the area supplied by the artery.
Color and Temperature Changes
When a DVT blood clot impedes much of the blood flow from the arm, the backed-up blood causes the hand and arm to feel warm and appear dark red, purplish or bluish. Superficial vein blood clots are almost always accompanied by significant inflammation of the surrounding vein -- a condition known as thrombophlebitis. This inflammation causes the skin overlying the vein to be bright red and warm. Arterial blood clots typically cause the skin in the area supplied by the artery to become pale and cool, as less blood enters the region.
Firm or Enlarged Veins
When a blood clot forms in a superficial vein, the vein may feel firmer than usual. This might not be obvious initially, but over time the clot generally becomes more solid and firmer. Furthermore, the vein distal to the clot -- that is, the area of the vein farthest from the upper arm -- may appear enlarged because of the clot's damlike effect. With a DVT blood clot, similar changes occur, but they are not observed because the vein is hidden deep within the arm. Nevertheless, when blood flow is blocked by a clot in the axillary or subclavian vein, some of the blood can be diverted through other veins in the area. This can produce enlarged superficial veins in the upper arm, shoulder and upper chest.
A mild fever up to about 100.4 F may occur as part of the body's response to any type of blood clot. A high fever suggests the presence of an infection, which may be located either in the vein with the clot -- a condition called septic thrombophlebitis -- or in another area. Numbness, tingling or weakness in the hand or arm may occur with an arterial blood clot if nerve or muscle function becomes impaired because of an inadequate blood supply. DVT blood clots that cause significant swelling can increase the pressure within the arm. This condition, known as a compartment syndrome, can also impede nerve or muscle activity in the area.
Warnings and Precautions
DVT blood clots can lead to pulmonary emboli. These are pieces of clot that break free and travel through the bloodstream to the lung, where they block a pulmonary artery. Pulmonary emboli occur in at least 3 to 12 percent of people with an arm DVT blood clot, according to a June 2011 article in "Vascular Medicine." Sudden shortness of breath, chest pain and a cough -- sometimes with blood-tinged mucus -- are typical symptoms. Large pulmonary emboli can cause lightheadedness, loss of consciousness and even death. Pulmonary emboli rarely occur with superficial vein blood clots.
Arterial blood clots do not cause pulmonary emboli, but parts of the clot may break off and become trapped in the smaller arteries of the arm, especially in the fingertips. Complete blockage of these vessels can eventually lead to brown or black skin discoloration and other symptoms of gangrene -- a condition characterized by localized tissue death.
When to Seek Medical Attention
If you have symptoms of a blood clot in your arm, see your doctor promptly to establish the diagnosis and begin appropriate treatment. Even if your doctor determines that you do not have a blood clot, you may have another serious condition causing these symptoms, such as an infection. Furthermore, your doctor will be able to investigate whether you have an underlying medical disorder that led to the clot, such as cancer, atherosclerosis or a heart rhythm abnormality called atrial fibrillation.
Seek emergency medical care if you develop severe pain or swelling, or sudden paleness or coldness of your arm. Also obtain immediate medical attention if you experience symptoms suggestive of a pulmonary embolus.
Reviewed by: Tina M. St. John, M.D.