The dangers within: how blood clots affect your health

illustration of VTEA healthy blood flow is something we take for granted – the assumption our veins will keep the vital fluid moving through our body at a healthy rate. But sometimes blood flow slows and clots form, wreaking havoc on our health.

A blood clot, or thrombus, can move through the blood stream until it gets stuck in a narrow passageway, becoming what is called an embolus. The blood can no longer pass through the veins and reach organs. An embolus in a coronary artery can cause a heart attack, in a cerebral artery, it can cause a stroke.

In the veins, a blood clot is called a venous thromboembolism (VTE), and it has two related conditions: deep vein thrombosis (DVT) and pulmonary embolism (PE). When they occur, they require immediate medical attention.

DVT and PE

Deep vein thrombosis affects over 1.2 million people in the U.S. It happens when a clot forms in a vein deep in the body, as opposed to a vein that runs close to the body’s surface.
DVT usually occurs in one leg, mainly affecting the large veins in the calf and thigh.

About half of people experiencing DVT don’t show outward signs or symptoms. When symptoms do occur, they show up in the leg that has a clot and may include:

  • Changes in skin color (redness)
  • Leg pain or tenderness, especially in the calf
  • Leg swelling (edema)
  • Skin that feels warm to the touch

Pulmonary embolism, or PE, occurs when a clot reaches the lung, causing a blockage that can cause permanent injury. This lowers the blood’s oxygen level and potentially damages other organs. Blood clots that travel to the lungs are more likely to have formed and broken away in the thigh rather than in the lower leg or other parts of the body.
Symptoms that arise for PE include:

  • Unexplained shortness of breath
  • Rapid breathing
  • Chest pain (may be worse upon deep breath)
  • Rapid heart rate
  • Lightheadedness/fainting
  • Coughing up blood.

DVT and PE are serious, potentially life-threatening conditions that require immediate medical attention to prevent further complications.


VTE is an equal opportunity condition and can affect people of either gender, all ages, races and ethnicities. But some risk factors are stronger than others. Increasing age (from 40 on) means increased risk.

Experiencing surgery, major trauma, fractures of the hip or leg, also carries strong risk. Other independent risk factors include:

  • Active cancers and chemotherapy
  • Prior superficial vein thrombosis
  • Infection
  • Varicose veins
  • Inherited thrombophilia (a condition that tends to make the blood clot more easily)
  • Kidney disease
  • Prolonged immobility such as hospital or nursing home confinement or leg paralysis

And among women:

  • Use of oral contraceptives
  • Pregnancy/postpartum period
  • Hormone therapy

Any of the following factors alone may not justify preventive measures for VTE, but a combination of two or more may be cause for action and may affect the length and type of treatment someone receives:

Prior VTE — People who have had a previous episode of VTE have a high risk of recurrence. In one study, patients with a history of VTE were eight times more likely to develop a new episode during a high-risk period, such as surgery or serious illness, than patients without such a history.
Age — People over 40 are at higher risk, and that risk doubles with each subsequent decade.
Cardiac or respiratory failure
Immobility — Prolonged immobility like on very long flights, combined with other major risk factors, increases the chances of VTE.
Oral contraceptives — Women who use estrogens for contraception or menopause and men receiving
estrogen therapy for prostate cancer are at increased risk for VTE.
Some inherited or acquired blood conditions, such as antiphospholipid antibody syndrome.
Being pregnant or having had a baby recently puts a woman at greater risk of developing a blood clot.
Risks also increase when the following apply:

  • Previous blood clots
  • Genetic predisposition to blood clots
  • Obesity
  • Multiple births
  • Other illness, such as cancer and serious infection


Diagnosis is done by assessment — a health care professional gathers information about a person’s medical history, age, medications and specific lifestyle factors.
A Doppler ultrasound may be performed on the legs and certain blood tests that detect a greater chance of blood clotting may be performed. Additional testing with CT angiography (a test used to see arteries and veins throughout the body) may be done if PE is suspected.


After a medical assessment, those at risk may receive treatment to prevent clots from forming, such as:

  • Anti-clotting, blood-thinning medications
  • Wearing compression stockings or using an intermittent compression device that helps keep blood from pooling in the deep veins
  • Being instructed to move around or do foot/leg exercises when immobile for long periods.


  • This potentially life-threatening condition requires immediate medical attention. A medical team will want to stop the clot from getting bigger, keep the clot from breaking off and travelling into the lungs, and prevent another clot from forming. Treatment includes: Anticoagulants to break up clots and prevent new ones. For example, injectables such as heparin or low-molecular-weight heparin, or tablets such as apixaban, dabigatran and rivaroxaban, edaxaban and warfarin.
  • Equipment such as compression stockings and air compression cuffs and garments for the legs, calves, arms or chest that fill with compressed air and help increase blood flow.
  • Thrombolytic therapy using drugs such as a tissue plasminogen activator, which is a clot-dissolving enzyme.

In rare cases, when medicines don’t work, surgery may be needed. It may involve placing a filter in the body’s largest vein to prevent blood clots from traveling to the lungs, removing a large blood clot from the vein or injecting clot-busting medicines.

Pulmonary embolism is the most common preventable cause of death among hospital patients. Data from randomized trials involving general surgical patients suggest prevention measures in high-risk patients can prevent VTE in 1 of 10 patients and save the life of about 1 of 200 patients.

The good news is hospitals are doing a better job of managing the condition. Recent research has focused on development of noninvasive diagnostics such as ultrasound enhanced techniques and molecular imaging methods.

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