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Embolism, Blood Clot

An embolus is anything that blocks the flow of blood in a vessel, it could be a blood clot or a foreign body like air. For the purpose of this article, we would be focusing on embolism caused by blood clots. When the blood flow is compromised, oxygen supply is cut off and this will lead to poor function and eventually death of the organ being supplied.


The symptoms can either be mild or severe. They may begin suddenly or increase over time depending on the size of the embolus and how much blood flow is compromised. Symptoms also depend on the organ involved but generally involves pain and loss of function.


There are various investigations that can be done to check for the presence of an embolus, the extent of damage of an embolus and the risk of developing an embolus.

  • Ultrasound, especially colored Doppler ultrasound is used to examine the arteries, it can also be applied through the transcranial route. 
  • MRI and CT scan of the brain with contrast to show the area of the infarct and the level of damage done to the brain. 
  • Echocardiography and electrocardiography is used to diagnose a myocardial infarction. Specialized techniques like transesophageal echocardiography may be involved [7].
  • Arteriography can also be done and when the use of contrast is required to be kept to a minimum, digital subtraction angiography is used.
  • Angioscopy is used to visualize the artery directly by passing a flexible catheter into it.
  • Blood tests are done to measure the level of enzymes on the body. Many of these enzymes are increased in embolization especially of the heart. Blood tests will also show if there are any underlying infection. Blood tests are also used to test for coagulation factors.


The goal of treatment is to minimize symptoms and increase perfusion to the affected area. It involves the use of thrombolytics to dissolve the clot, anticoagulants like heparin to thin the blood and prevent further clotting. Painkillers are giving to reduce the pain and vasodilators to relax and dilate the blood vessels.

Sometimes, surgery may be indicated and this includes, embolectomy which is done to reduce the embolus and arterial bypass surgery done to create a new blood supply [8]. In cases where the limb is affected and it has developed to gangrene, the affected limb should be amputated.


The prognosis of a patient depends on the area affected by the clot and the extent to which blood flow is compromised. If medical intervention is not sought, mortality rate is as high as 30%. The affected part could also be permanently damaged leading to loss of that part, e.g in amputation. There is a chance of recurrence of this condition even after successful treatment [5].


In normal individuals, clotting factors are responsible for prevention of excessive blood loss when there is a bleeding episode. In some individuals, formation of blood clots happen even without a bleeding episode, these individuals are said to be at risk of clot formation. Some of the risk factors for clot formation are heart disease, hypercholesterolemia, smoking, hypertension, and atherosclerosis.

Another cause is stasis of blood flow. This could lead to clots and it is the primary cause of pulmonary embolism. Factors that contribute to this are sitting on long flights, prolonged best rest, immobilization of the leg, cancer, previous surgery and some genetic conditions that predispose an individual to clot formation [2].


Over 500,000 deaths result each year from heart-related condition caused by arterial embolism, and half of these are women. Half of these deaths are in individuals who have not reached their life expectancy. Venous thromboembolism also occurs in as much as 100 per 100,000 individuals with the incidence increasing with age to as high as 600 in 100,000 in those above 80 years. Death occurs in about 6% of deep venous thrombosis (DVT) cases and the incidence is equal in both male and females. Embolism is slightly commoner in Caucasians and Negroes than in Hispanics and Asians[3].

Sex distribution
Age distribution


Due to some of the factors listed above, a clot begins to form in a vessel. This clot is known as a thrombus. The thrombus then dislodges and begins to travel within the circulation, mostly in the direction of blood flow and is now called an embolus. When it gets to a vessel it is too big to pass through, it lodges and blocks the lumen preventing further blood flow. This will lead to ischemia of the supplied area as oxygen supply is compromised leading to tissue hypoxia and eventually necrosis. The specific pathophysiology depends on the organs and areas supplied [4].


This involves reducing the risk factors and steps include healthy diet, avoid excessive salt in diet, losing weight if overweight or obese, regular exercise, stop smoking.


The most important conditions that result from an embolism are stroke, myocardial infarction and pulmonary embolism. The symptoms of embolism are usually very acute and prompt medical intervention is required [1].

Patient Information

  • Definition: When a blood clot forms in within an intact vein or artery, it is called a thrombus. When this clot dislodges, it is called an embolus. Embolism is what results when this embolus travels and blocks the blood supply to a particular part of the body or organ like heart or lungs.
  • Causes: Risk factors for formation on clots include heart disease, cancer, pregnancy, obesity, increased cholesterol, hypertension and advancing age. Also, anything that can cause long periods of immobility e.g long flights and prolonged bed rest can lead to formation of clots.
  • Symptoms: These are generally specific for the organs affected. They include pain and loss of function. There is chest pain, cough and shortness of breath in myocardial infarction and pulmonary embolism while stroke may present with unconsciousness and paralysis.
  • Diagnosis: These involve a series of imaging tests and blood tests. These are used to know where the clot is and the extent of damage.
  • Treatment: This involves the use of drugs to melt the clots and prevent further clots from forming and pain killers to manage the pain. Surgery may also be indicated to remove the clot or a bypass surgery to restore blood flow.



  1. Bates SM, Greer IA, Pabinger I, Sofaer S, Hirsh J. Venous thromboembolism, thrombophilia, antithrombotic therapy, and pregnancy: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Chest. Jun 2008;133(6 suppl):844S-886S.
  2. Couturaud F, Leroyer C, Julian JA, et al. Factors that predict risk of thrombosis in relatives of patients with unprovoked venous thromboembolism. Chest. Jul 10 2009;epub ahead of print.
  3. Roberts LN, Patel RK, Arya R. Venous thromboembolism and ethnicity. Br J Haematol. Aug 2009;146(4):369-83.
  4. Kearon C, Julian JA, Kovacs MJ, et al. Influence of thrombophilia on risk of recurrent venous thromboembolism while on warfarin: results from a randomized trial. Blood. Dec 1 2008;112(12):4432-6.
  5. Perez A, Merli GJ. Novel Anticoagulant Use for Venous Thromboembolism: A 2013 Update. Curr Treat Options Cardiovasc Med. Feb 6 2013
  6. Qaseem A, Snow V, Barry P, Hornbake ER, Rodnick JE, Tobolic T, et al. Current diagnosis of venous thromboembolism in primary care: a clinical practice guideline from the American Academy of Family Physicians and the American College of Physicians. Ann Fam Med. Jan-Feb 2007;5(1):57-62.
  7. Geerts WH, Code KI, Jay RM, Chen E, Szalai JP. A prospective study of venous thromboembolism after major trauma. N Engl J Med. Dec 15 1994;331(24):1601-6. 
  8. Garcia D, Ageno W, Libby E. Update on the diagnosis and management of pulmonary embolism. Br J Haematol. Nov 2005;131(3):301-12. 

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Last updated: 2017-08-09 18:08