A pulmonary embolism (PE) is a sudden and serious blockage in an artery within the lungs. This blockage is most often caused by a blood clot that has traveled from another part of the body, commonly originating in the deep veins of the legs, a condition known as deep vein thrombosis (DVT). When such a clot, or embolus, lodges in a lung artery, it restricts blood flow to a portion of the lung, which can lead to lung tissue damage and reduced oxygen levels in the body.
Underlying Health Conditions
Certain medical conditions and treatments elevate the risk of developing a pulmonary embolism. Individuals who have undergone recent surgery or major trauma face an increased risk, particularly following orthopedic procedures like hip or knee replacement. Immobility during and after such procedures, combined with tissue damage, can slow blood flow and promote clot formation within veins. The risk of PE is generally highest within the first five weeks post-surgery.
Cancer and its associated treatments also contribute to a heightened risk of blood clots. Many cancers can induce a hypercoagulable state, meaning the blood is more prone to clotting. This occurs due to the release of procoagulant substances and inflammatory markers by tumor cells. Chemotherapy further increases this risk.
Heart conditions like heart failure, atrial fibrillation, or a history of heart attack can also predispose individuals to pulmonary embolisms. These conditions can lead to reduced blood flow or contribute to the formation of clots that can then travel to the lungs. Atrial fibrillation is an established risk factor for both ischemic stroke and PE.
Some individuals are born with inherited clotting disorders, known as thrombophilia, which make their blood more likely to clot. Examples include the Factor V Leiden mutation and the prothrombin gene mutation. Inflammatory bowel diseases (IBD), such as Crohn’s disease and ulcerative colitis, also increase PE risk due to chronic inflammation.
Lifestyle Habits and Situations
Daily habits and specific situations can also raise the likelihood of a pulmonary embolism. Prolonged immobility, such as extended periods of sitting during long-haul flights or prolonged bed rest, can significantly slow blood flow in the veins, increasing the chance of clot formation. This slowed circulation allows clotting factors to accumulate, making the blood more prone to forming a thrombus.
Obesity is another factor that elevates PE risk. Excess body weight puts additional strain on the veins and is associated with a state of chronic low-grade inflammation, both of which can contribute to blood clot formation. The risk of venous thrombosis increases with higher body mass index (BMI).
Smoking also increases the risk of blood clots and, consequently, pulmonary embolism. The chemicals in tobacco smoke damage the inner lining of blood vessels, making them more susceptible to blockages and promoting inflammation. Smoking also makes blood platelets stickier, encouraging them to clump together.
Insufficient fluid intake, or dehydration, can also contribute to the risk of blood clots. When the body is dehydrated, blood can become thicker and more viscous, which slows down circulation. This increased viscosity can elevate the risk for DVT and PE, especially during periods of prolonged sitting such as air travel.
Central venous catheters, which are medical devices inserted into large veins, can also be a site for clot formation. The catheter can cause irritation and damage to the vein wall, leading to inflammation, and can also alter normal blood flow, promoting blood stasis. The risk is influenced by factors like catheter diameter, location, and the duration it remains in place.
Hormonal and Reproductive Factors
Hormones and reproductive health play a role in pulmonary embolism risk. Estrogen-containing medications, such as combined oral contraceptives and hormone replacement therapy (HRT), can increase the blood’s clotting ability. Estrogen increases the plasma concentration of various clotting factors. The risk associated with oral contraceptives is generally 3-5 times higher than in non-users.
Pregnancy and the postpartum period also carry an elevated risk of pulmonary embolism. During pregnancy, the body experiences an increase in blood volume and pressure on veins, which can slow blood flow. Hormonal changes also increase the likelihood of blood clotting to limit blood loss. The postpartum period has a particularly high risk due to these hormonal shifts and potential trauma from childbirth.
History of Blood Clots and Age
A history of previous deep vein thrombosis (DVT) or pulmonary embolism (PE) is a significant predictor for future clots. Having experienced a blood clot in the past is considered the most impactful risk factor for recurrence. The risk of recurrence after a first episode of VTE can be as high as 5% to 7% per year.
The risk of pulmonary embolism also increases with age, particularly after 60 years. This heightened susceptibility in older individuals is often due to reduced mobility and the increased prevalence of underlying health conditions that contribute to clot formation.