Blood Clots and Associated Risk Factors?

By Tara McDougall & Alicia Walczak

Have you ever sustained an injury to your leg and gone to the doctor only to be told that you have nothing to worry about? Have you ever spent several hours traveling without standing up and moving around? Have you ever been ordered on bed rest by a doctor but not told of the danger of staying in bed for more then a few days without exercising your legs? Do you have atherosclerosis or a blood disorder? These are all risk factors for developing a deep vein thrombosis (DVT).

To understand what a blood clot (also known as a thrombus) is and how it works, it is important to first understand what blood is. There are four major components to blood:

  1. Red blood cells, which carry oxygen to our tissues
  2. White blood cells, which help fight disease and infection
  3. Plasma which carries nourishment and accounts for much of our blood volume
  4. Platelets which cause blood to clot

Each component of blood and the vessels through which it flows, helps ensure that oxygen rich blood reaches our tissues via the arteries and oxygen poor blood is taken back to the lungs via the veins to become reoxygenated. When there is an interruption in blood flow such as an injury, each of the components work together to help repair the injury and stop blood loss.

Platelets, or thrombocytes, are responsible for stopping blood loss through vascular (blood vessel) damage/injury. The formation of a platelet plug, more commonly known as a scab, stops blood from leaving the site of an injury. A thrombus is a blood clot that is formed at the site of injury. Sometimes thrombi form without the provocation of injury around valves in the deep veins of the leg, hence the term, deep vein thrombosis.

Pulmonary embolism is a condition closely related to DVT. A pulmonary embolism occurs when a piece of the blood clot breaks away from the thrombus and travels to the pulmonary arteries thereby blocking blood flow to the lungs. It is not known why a blood clot dissolves for some people and for others it travels to the lungs. However, DVT is a potentially life threatening situation.

More than half of people with pulmonary embolisms do not have symptoms.

Who is at risk for developing DVT?

Virchow's Triad

Over 150 years ago, a prominent German Doctor, Roudolph Virchow, surmised that thrombus formation and propagation stemmed from abnormalities in three vascular areas, now known as Virchow's Triad. The three main components of Virchow’s Triad, and how they relate to DVT, are:

Blood flow

  1. Abnormalities of blood flow such as injury to an artery or vein. This includes undergoing major surgery
  2. Pregnancy, and up to 6 weeks following birth (blood vessels can become compressed causing less blood flow to the tissues
  3. You are over 60 years of age

Vessel walls

Injury to the endothelium (the lining of arteries) such as caused by smoking, initiates a process by which a fatty plaque (atheroma) accumulates in the injured area and thus reduces blood flow. Subsequent studies determined that in the case of hyper-cholesterolemia, fat-laden particles can infiltrate the vessel walls in the absence of injury to the endothelium.

Blood components

  1. abnormalities in coagulation (blood clotting) and fibrinolytic pathways (the phases of blood clotting)
  2. Cancer treatments (cancer treatments don’t just affect the cancer, they also sometimes attack healthy blood cells)
  3. Family history of blood disorders
  4. Diseases contributing to abnormally thick blood

Signs and Symptoms

See a doctor right away if you experience any of the following symptoms because you may have a deep vein thrombosis or a complication from a DVT known as a pulmonary embolism:

  1. swelling of the leg or along a vein in the leg
  2. pain or tenderness in the leg which you may feel only when standing or walking
  3. Increased warmth in the lower leg
  4. red or discoloured skin on the lower leg
  5. unexplained shortness of breath
  6. pain with deep breathing
  7. coughing up blood

Questions to ask your doctor if you think you might have a blood clot

  1. Do I have to go to the hospital for treatment?
  2. What kind of medication do I have to take?
  3. Will my blood clot go away if I don’t receive treatment?
  4. Is there anything I can do to prevent one from occurring?
  5. How long does it take to dissolve?

How is it diagnosed?

Your doctor will acquire your medical history, perform a physical, run a series of tests, and identify possible risk factors you may have. Medical history includes your current state of health, any prescriptions you are taking, recent surgeries or injuries, and if you have cancer. A physical examination will include your doctor checking your leg for signs of a blood clot, checking that your blood pressure is in the normal range, and if your heart and lungs are functioning normally. Your doctor willalso run a series of tests to help detect if you have a blood clot. These tests include an ultrasound, which is the most common, a D-dimer test or a venography. Your doctor also may order an MRI or a CAT scan.

Treatment/ Prevention

The main goal of treatment is to stop the clot from growing or having it move into the lungs. Both are very serious. Another goal is to reduce the chance of reoccurrence. The following are treatments that one can expect:

Anticoagulants: decrease the body’s ability to clot
Blood thinners: thin the blood. They are typically given in pill form or via injection for 3-6 months
Thrombin Inhibitors: interfere with the bloods ability to clot
Thrombolocytes: quickly dissolve large clots in a more serious case

Other treatments include a vena cava filter or compression stockings


  1. See your doctor regularly for check ups.
  2. Make sure you always take any medications you are prescribed by your doctor.
  3. Exercise your lower legs during long trips by standing up and moving around or stretching your legs.
  4. While seated, keep your heels on the floor and practice slowly raising and lowering your toes. Then, keep your toes on the floor, and slowly raise and lower your heels. Try to do this for 2-3 minutes every hour.
  5. Drink lots of fluid and avoid alcohol.
  6. Make sure to ask your doctor about possible exercises to perform if you are on bed rest from an injury or surgery or if you require compression stockings.
  7. If you are unsure about your condition don’t be afraid to ask your doctor any questions you may have or get a second opinion if you disagree with your diagnosis.


  1. US Department of Health and Human Services, (2010). Deep Vein Thrombosis. Retrieved from: http://www.nhlbi.nih.gov/health/dci/Diseases/Dvt/DVT_WhatIs.html
  2. Aurora Healthcare, (2010). Traveling with Heart Disease. Retrieved from: http://www.aurorahealthcare.org/yourhealth/healthgate/getcontent.asp?URLhealthgate=%2246088.html%22
  3. Everyday Health Inc, (2011). Questions to Ask Your Doctor About Blood Clots (Venous Thromboembolism). Retrieved from: http://www.everydayhealth.com/dvt/ask-your-doctor-about-blood-clots.aspx
  4. MDlinx, (2011). Summary of Pulmonary Embolism. Retrieved from: http://www.patientlinx.com/blooddisorders/pesummary.cfm
  5. US Department of Health and Human Services, DVT Fact Sheet. Retrieved on February 7, 2011 from: http://www.surgeongeneral.gov/topics/deepvein/calltoaction/factsheetdvt_pe.html

The articles, on the Cardiac Health Foundation of Canada website, are presented with the understanding that the Foundation is providing information only and not rendering medical advise. Please check with your family physician, specialist or health care professional before implementing any of the ideas expressed in these articles.