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What are blood clots? And what causes them?

Medical Moments, Press Releases, Uncategorized

Dr. Paul Koelliker
Dr. Paul Koelliker

Blood naturally clots to prevent or minimize bleeding during trauma or with wounds. Sometimes the clotting mechanism that causes our blood to clot can create clots when they are unneeded or unwanted.

When clots form in our veins they cause a medical condition called Venous Thrombosis and in rare instances the clotted veins can cause enough vascular congestion to cause local problems.

The main concern for venous thrombosis, however, is embolization of the clot to the lungs.

Embolization of a venous clot from the lungs is a condition where the clotted blood breaks free and travels through veins to the right side of the heart. The clot passes through the heart and becomes lodged in the vascular system of the lungs. This condition is called a Pulmonary Embolism (PE). PEs can be life threatening and cause chest pain, shortness of breath.  Large centrally located PEs can cause coughing blood and decreased blood pressure. They can be fatal.

The most common site for blood clots to develop is the veins of the lower extremity.  

Veins in the calf tend to form clots first, and can be recognized by local pain and swelling relative to the other leg. Clots below the knee rarely embolize, but can grow and propagate up the venous system of the leg to involve the large veins in the thigh.

Clots can easily embolize from the femoral vein in the thigh. The goal of treatment is to recognize the clot before it embolizes and treat it with medications that decrease the ability of the blood to clot.

Blood clots can less-commonly form in other veins including the veins of the upper extremity or veins deep in the pelvis. These atypical sites are more difficult to diagnose with clots and pelvic vein thrombosis may present with a pulmonary embolism without prior symptoms.

Diagnosis or clots in the extremities is usually made with ultrasound. A specific ultrasound can detect clots before they embolize so treatment can begin. Blood clots that have travelled to the lungs usually are diagnosed with a CAT scan using a vascular dye. Other diagnostic modalities exist but are less commonly used.

Treatment for venous thrombosis and PE are similar. Patients are placed on blood thinning agents (medications that decrease the blood’s ability to clot). Usually treatment consists of shots of a medication in the low molecular weight Heparin category, and patients are transitioned to oral anti-coagulants like Coumadin or Pradaxa.

Risk factors for developing blood clots are both genetic and environmental. The triad of trauma, stasis and hypercoagulability are recognized risk factors.

Trauma can refer to the trauma of having surgery (especially orthopedic) as well as traumatic injury.  Stasis refers to decreased blood flow returning from the extremities, which occurs with immobilization from casts or splints as well as long travel with decreased mobility.

Hypercoagulability refers to a patient’s blood being more likely to clot than usual.  Hypercoagulability can be genetic (and sometimes evident in a family history) and there are a number of diseases/conditions that can cause this.

Hypercoagulability also occurs in smokers. Cigarette smoking is one of the highest risk behaviors for forming unwanted blood clots.

Medications can also increase the tendency to clot, and hormone therapy, especially birth control, can up the risk.

What can a person do to prevent blood clots?  

  • Avoidance of cigarettes is the easiest and most effective way to mitigate risk.
  • Taking time to get up and move around during long flights or stopping while driving and walking around also helps circulate blood before it can clot.
  • Taking aspirin for its anti-coagulant effect during long travel can decrease the risk as well.
  • After surgery, your doctor may recommend being on a blood-thinning agent for a period if they feel your risk is high.

If you feel that you have symptoms of a blood clot, you should discuss them with your physician or be seen in an Emergency Department to have diagnostic testing done.