Blood clots: what they are and how they become problems

Blood flows continuously throughout one’s body with the job of delivering oxygen to tissues and removing waste products created from cellular metabolism. The blood within arteries and veins clots to stop bleeding when needed, thus blocking the blood vessels.

Veins return blood from areas of the body back to the heart, and arteries carry blood away from the heart. When either arteries or veins are blocked (occluded) unnecessarily, a medical intervention may be necessary that requires hospitalization. An excessive blockage, also known as a thrombus, can cause strokes, heart attacks, loss of extremities, or internal organ damage.

Blood clots (thrombi) can occur in blood vessels, specifically deep veins or arteries. The clot formation occurs from hormonal triggers that occur when blood vessels are damaged, Platelets are tiny objects within blood that can group together to form a plug by sticking to walls of blood vessels.

Clotting factors, which are proteins in the blood, cause a reaction that makes the platelets stick together with red blood cells. Finally, there are other proteins that stop the reaction so that the clot is only as big as it needs to be. When the reaction is not slowed, the clot can create problems.

Risk factors for a Deep Vein Thrombus (blockage) DVT

• Prolonged immobility
• Surgery to an arm or leg, including casting for a broken bone
• Trauma
• Pregnancy
• Inherited blood clotting disorders
• Smoking
• Hormone therapy, including birth control pills

Risk factors for Arterial Thrombus (blockage)

• Smoking
• Diabetes
• Obesity (a body mass index over 30)
• High blood pressure
• High cholesterol
• Increasing age, especially after reaching 50 years of age
• A family history of peripheral artery disease, heart disease or stroke
• High levels of homocysteine (a protein component that helps build and                                         maintain tissue)

Treatment goals and options

The main goals of treatment are:

1. To prevent blood clots from getting larger
2. To prevent travel to the lungs (known as a pulmonary embolus) or other parts of the body
3. To prevent pain, skin sores, or swelling of extremities (known as post-thrombotic syndrome

Treatment options include blood thinners, stents, or procedures to remove clots.

Blood thinners (anticoagulants) don’t “thin” your blood, but they do keep a clot from growing or breaking off. This prevents new clots from forming. Some popular blood thinners are:

• Apixaban (Eliquis)
• Betrixaban (BEVYXXA)
• Dabigatran (Pradaxa)
• Edoxaban (Savaysa)
• Fondaparinux (Arixtra)
• Heparin
• Rivaroxaban (Xarelto)
• Warfarin (Coumadin)

In the hospital, treatment may start with injections of heparin through an intravenous catheter or under the skin. Conversion to Coumadin may be done prior to discharge, since this medication can be taken orally.

Blood tests will be done to determine if the right amount of the medication is within your system. Newer medications, known as Xa inhibitors, work as well as Coumadin without requiring blood tests for follow-up.

The body will eventually dissolve clots, but sometimes catheters are used to break them up faster (catheter directed thrombolyis). This procedure is done particularly when clots are larger, involve the arm, or the patient is at risk for pulmonary embolism. The method spares valves that are within veins and restores blood flow quickly, but it does increase the risk of bleeding problems and stroke.

If the catheter approach isn’t successful or possible, the last option would be surgical procedures. In arteries, the procedure is called an arterial embolectomy; in veins, a venous thrombectomy. 

Lastly, in prior decades filters were placed in a large vein known as the inferior vena cava (IVC) with hopes of stopping further spread of clots. Filters have fallen out of favor since 2010 due to adverse events.

Stents, on the other hand, are currently placed within veins and arteries. The stents open the vessel up or provide a pathway to deliver medications to the area of clot.

Sean J. Ennevor, M.D. graduated with a B.A.S. in biology and economics from Stanford University, and as a Dean’s Scholar from UCLA School of Medicine where he received his MD. He completed his medical residency and fellowship in anesthesiology at Yale University, where he was chief resident and on staff. He practiced medicine in the Twin Cities for over 14 years, and presently serves as an advisor and investor for medical technology companies throughout the country.