Animation of the formation of an occlusive thrombus in a vein. A few platelets attach themselves to the valve lips, constricting the opening and causing more platelets and red blood cells to aggregate and coagulate. Coagulation of unmoving blood on both sides of the blockage may propagate a clot in both directions.

A thrombus occurs when the hemostatic process, which normally occurs in response to injury, becomes activated in an uninjured or slightly injured vessel. A thrombus in a large blood vessel will decrease blood flow through that vessel (termed a mural thrombus). In a small blood vessel, blood flow may be completely cut off (termed an occlusive thrombus), resulting in death of tissue supplied by that vessel. If a thrombus dislodges and becomes free-floating, it is considered an embolus.

Some of the conditions which elevate risk of blood clots developing include atrial fibrillation (a form of cardiac arrhythmia), heart valve replacement, a recent heart attack (also known as a myocardial infarction), extended periods of inactivity (see deep venous thrombosis), and genetic or disease-related deficiencies in the blood’s clotting abilities.

Formation

Platelet activation can occur through different mechanisms such as a vessel wall breach that exposes collagen, or tissue factor encryption.[clarification needed] The platelet activation causes a cascade of further platelet activation, eventually causing the formation of the thrombus.[2]This process is regulated through thromboregulation.

  • Illustration Comparing Normal Artery vs Diseased Artery with a Blood Clot

  • Micrograph showing a thrombus (center of image) within a blood vessel of the placenta. H&E stain.

  • Illustration depicting thrombus formation over arterial plaque.

Prevention and treatment

Main articles: Thrombolysis, Thrombosis prophylaxis, and Reperfusion therapy

Blood clot prevention and treatment reduces the risk of stroke, heart attack and pulmonary embolism. Heparin and warfarin are often used to inhibit the formation and growth of existing thrombi; the former binds to and activates the enzyme inhibitor antithrombin III, while the latter inhibits vitamin K epoxide reductase, an enzyme needed to synthesize mature clotting factors.

Some treatments have been derived from bacteria. One drug is streptokinase, which is an enzyme secreted by several streptococcal bacteria. This drug is administered intravenously and can be used to dissolve blood clots in coronary vessels. However, streptokinase is nonspecific and can digest almost any protein, which can lead to many secondary problems. Another clot-dissolving enzyme that works faster and is more specific is called tissue plasminogen activator (tPA). This drug is made by transgenic bacteria and it converts plasminogen into the clot-dissolving enzyme plasmin.[3] There are also some anticoagulants that come from animals that work by dissolving fibrin. For example, Haementeria ghilianii, an Amazon leech, produces an enzyme called hementin from its salivary glands.[4] As of 2012, this enzyme has now been successfully produced by genetically engineered bacteria and administered to cardiac patients.

Prognosis

Thrombus formation can have one of four outcomes: propagation, embolization, dissolution, and organization and recanalization.[5]

  1. Propagation of a thrombus occurs towards the direction of the heart. This means that it is anterograde in veins or retrograde in arteries.
  2. Embolization occurs when the thrombus breaks free from the vascular wall and becomes mobile. A venous embolus (mostly from deep vein thrombosis in the lower limbs) will travel through the systemic circulation, reach the right side of the heart, and travel through the pulmonary artery resulting in a pulmonary embolism. Arterial thrombosis resulting from hypertension or atherosclerosis can become mobile and the resulting emboli can occlude any artery or arteriole downstream of the thrombus formation. This means that cerebral stroke, myocardial infarction, or any other organ can be affected.
  3. Dissolution occurs when the fibrinolytic mechanisms break up the thrombus and blood flow is restored to the vessel. This may be aided by drugs (for example after occlusion of a coronary artery). The best response to fibrinolytic drugs is within a couple of hours, before the fibrin meshwork of the thrombus has been fully developed.
  4. Organization and recanalization involves the ingrowth of smooth muscle cells, fibroblasts and endothelium into the fibrin-rich thrombus. If recanalization proceeds it provides capillary-sized channels through the thrombus for continuity of blood flow through the entire thrombus but may not restore sufficient blood flow for the metabolic needs of the downstream tissue.[citation needed]

Stroke in women

A number of factors are likely behind the surprising rise in strokes in women, including:

  • Increasing rates of obesity (women’s waists have grown by nearly two inches in the last 10 years)
  • Vitamin D3 deficiency due to lack of sun exposure. Sun avoidance also increases your risk of vitamin D sulfate deficiency, which may be an underlying cause of arterial plaque buildup (a risk factor for stroke)
  • Rising prevalence of high blood sugar levels
  • eating unprocessed, preferably organic, foods, exercising and maintaining a healthy weight will help to reduce your risk of stroke. Two additional risk factors that can have a direct impact on your stroke risk are:
    • Psychological distress. According to a 2008 study published in the journal Neurology, the more stressed you are, the greater your risk. The researchers actually found that for every notch lower a person scored on their well-being scale, their risk of stroke increased by 11 percent. Not surprisingly, the relationship between psychological distress and stroke was most pronounced when the stroke was fatal.
    • Hormone replacement therapy (HRT) and birth control pills. If you’re on one of the hormonal birth control methods (whether it’s the pill, patch, vaginal ring or implant), it is important to understand that you are taking synthetic progesterone and synthetic estrogen — something that is clearly not advantageous if you want to maintain optimal health. These contraceptives contain the same synthetic hormones as those used in hormone replacement therapy (HRT), which has well-documented risks, including an increased risk of blood clots, stroke, heart attack, and breast cancer.

Diet Soda May Dramatically Increase Your Stroke Risk

Earlier this year, research presented at the American Stroke Association’s International Stroke Conference showed that people who drink just one diet soda a day may increase their risk of stroke by 48 percent!

According to the authors:

“This study suggests that diet soda is not an optimal substitute for sugar-sweetened beverages, and may be associated with a greater risk of stroke, myocardial infarction, or vascular death than regular soda.”

While more research will likely be needed to confirm this potential link, there’s plenty of evidence showing that artificial sweeteners such as aspartame and sucralose (Splenda) can be dangerous to your health. I believe aspartame is, by far, the most dangerous artificial sweetener on the market. Reports of adverse reactions to the US FDA also support this, as aspartame accounts for over 75 percent of the adverse reactions to food additives reported to the FDA.

Embolism

An embolism is the lodging of an embolus, a blockage-causing piece of material, inside a blood vessel.[1] The embolus may be a blood clot (thrombus), a fat globule, a bubble of air or other gas (gas embolism), or foreign material. An embolism can cause partial or total blockage of blood flow in the affected vessel.[2] Such a blockage (a vascular occlusion) may affect a part of the body distant from where the embolus originated. An embolism in which the embolus is a piece of thrombus is called a thromboembolism. Thrombosis, the process of thrombus formation, often leads to thromboembolism.

An embolism is usually a pathologic event (that is, part of illness or injury). Sometimes it is created intentionally for a therapeutic reason, such as to stop bleeding or to kill a cancerous tumor by stopping its blood supply. Such therapy is called embolization.

Gender bias in treating or preventing blood clots in women

In health care, gender disparities are especially pernicious. If you are a woman, studies have shown, you are not only less likely to receive blood clot prophylaxis, but you may also receive less intensive treatment for a heart attack. If you are a woman older than 50 who is critically ill, you are at particular risk of failing to receive lifesaving interventions. If you have knee pain, you are less likely to be referred for a knee replacement than a man, and if you have heart failure, it may take longer to get EKGs.

When Dr. Elliott Haut and his team at Johns Hopkins Hospital in Baltimore designed their blood clot prevention protocol back in 2006, they didn’t expect to discover systemic gender bias. But the data were clear and the implications were alarming: Women who were trauma patients at Johns Hopkins Hospital were in considerably greater danger of dying of preventable blood clots than men.

Why? Because doctors were less likely to provide them with the appropriate blood clot prevention treatment. At Hopkins, as at many hospitals, both men and women were receiving treatment at less than perfect rates, but while 31 percent of male trauma patients were failing to get proper clot prevention, for women, the rate was 45 percent. That means women were nearly 50 percent more likely to miss out on blood clot prevention.

Blood clots, gelatinous tangles that can travel through the body and block blood flow, kill more people every year than breast cancer, AIDS and car crashes combined. But many of these clots can be avoided — if doctors prescribe the right preventive measures.

Such implicit bias, as researchers now understand, happens when we unintentionally use stereotypes or associations to make judgments. “Perhaps we take women’s symptoms less seriously, or we interpret them as having an emotional cause as opposed to a physical cause,” said Dr. Christine Kolehmainen, the associate director for women’s health at the Middleton Memorial Veterans Hospital in Madison, Wis. Studies bear this out: in one study of patients with irritable bowel syndrome, doctors were more likely to suggest that male patients receive X-rays and more likely to offer female patients tranquilizers and lifestyle advice.

In the case of blood clot prevention, doctors’ assumptions about women’s risk factors could lead to disparities in treatment. “There might be stereotypes about women’s biology or environment or occupation that could all play into medical decision-making,” Kolehmainen said.

Whether unintentional, unconscious or simply based on erroneous assumptions, treatment differentials clearly exist. Interventions like the Hopkins checklist can help correct them.

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