Pulmonary Embolism
Pulmonary embolism is a blood clot that blocks an artery in the lung. It is a medical emergency. Without prompt treatment, it can cause permanent lung damage, heart failure, or death.
It ranks third among the most common cardiovascular diseases worldwide, behind heart attack and stroke. About 900,000 people in the United States are affected each year. Roughly one in three people with an undiagnosed pulmonary embolism do not survive. With early treatment, that risk drops dramatically.
What Is Pulmonary Embolism?
A pulmonary embolism occurs when a blood clot travels through the bloodstream and lodges in an artery inside the lung. The clot blocks blood flow through that artery. The portion of lung tissue beyond the blockage cannot receive blood and stops exchanging oxygen properly.
When oxygen levels drop, the body cannot meet the demands of its organs and tissues. The right side of the heart, which pumps blood into the lungs, must push harder against the blocked artery. If the blockage is large or multiple clots are involved, this strain can overwhelm the right heart and cause it to fail.
Most pulmonary embolisms begin as a deep vein thrombosis, or DVT, a blood clot that forms in a deep vein most often in the leg or pelvis. The clot breaks free, travels up through the veins, passes through the right side of the heart, and reaches the lung arteries.
Pulmonary embolism is serious but very treatable when recognized early. Every minute between symptom onset and treatment matters.
At the BaleDoneen Method, identifying clotting risk factors and vascular conditions before events occur is central to preventing life-threatening emergencies like PE.
Types of Pulmonary Embolism
Not all pulmonary embolisms carry the same level of immediate danger. Severity depends on the size of the clot, how much of the lung circulation is affected, and how well the heart is coping.
Massive PE is the most severe form. A large clot or multiple clots block a major portion of lung blood flow. Blood pressure drops sharply. The right heart is under extreme strain. This is an immediate life-threatening emergency requiring the fastest possible intervention, often including clot-dissolving drugs or surgical removal.
Submassive PE involves significant blockage with signs of right heart strain visible on imaging or blood tests, but blood pressure remains stable. These patients are at high risk of deteriorating quickly and require close monitoring and aggressive treatment.
Low-risk PE causes milder symptoms. Blood pressure is stable and the right heart is functioning adequately. These cases are often managed with blood thinners, sometimes without a hospital stay, but still require careful medical supervision.
All three types can worsen rapidly. A person who appears stable can deteriorate within hours. Early diagnosis and appropriate classification determine which treatment is needed and how urgently.
Symptoms of Pulmonary Embolism
Symptoms of PE can range from subtle to severe and can appear suddenly with no warning. Some people feel symptoms within seconds of the clot lodging. Others have mild symptoms that worsen gradually over days.
The most common early symptom is sudden shortness of breath. It may occur at rest or with minimal activity. Breathing becomes rapid and difficult. This happens because the blocked artery reduces the lung’s ability to transfer oxygen into the blood.
Chest pain is another key symptom. It is typically sharp and stabbing and worsens when taking a deep breath, coughing, or leaning over. This type of pain, called pleuritic chest pain, reflects irritation of the lung lining. In some cases the pain is dull or pressure-like and can feel similar to a heart attack.
Other symptoms include a rapid or irregular heartbeat, dizziness or lightheadedness, coughing that may produce blood-streaked mucus, excessive sweating, and pale or bluish skin. Fainting or sudden collapse can occur when blood pressure drops severely.
Leg symptoms often precede a PE. One-sided swelling, pain, warmth, or redness in the calf or thigh are signs of DVT, the clot in the leg that has not yet traveled to the lung.
Seek emergency care immediately if you experience sudden unexplained shortness of breath, chest pain that worsens with breathing, fainting, or coughing up blood. Do not wait to see if symptoms improve. Call emergency services. See warning signs and symptoms and symptoms in women for additional guidance.
Why Pulmonary Embolism Cuts Off Oxygen
The lungs work by moving oxygen from inhaled air into the bloodstream and removing carbon dioxide from the blood into exhaled air. This exchange happens in tiny air sacs called alveoli, which are surrounded by a dense network of small blood vessels.
When a clot blocks a lung artery, blood cannot reach the alveoli served by that artery. Those alveoli still receive air but have no blood flowing past them to pick up oxygen. Oxygen exchange in that region stops.
If the blockage is large enough, oxygen levels in the blood fall. The body responds by breathing faster, trying to compensate. The heart beats faster to circulate the remaining oxygenated blood more quickly. Blood pressure in the pulmonary arteries rises as the heart pushes harder against the blockage.
The right ventricle, which is not built to sustain high pressure the way the left ventricle is, begins to strain. In a massive PE, the right heart can dilate and fail within hours. When right heart failure occurs, blood pressure throughout the body collapses. Organs stop receiving the oxygen they need. Without intervention this progression can be fatal.
This is why oxygen saturation monitoring matters so much in suspected PE. A reading below 92 percent signals significant compromise. A rapidly falling reading is a sign of deterioration that requires immediate escalation of care.
Causes of Pulmonary Embolism
Almost all pulmonary embolisms are caused by a blood clot that originates in a deep vein, most commonly in the legs or pelvis. The clot forms when blood pools, flows too slowly, or when the vessel wall is damaged.
Prolonged immobility is one of the most common triggers. Lying in a hospital bed after surgery, sitting through a long flight, or spending extended time in bed during illness all reduce blood flow through the leg veins. Stagnant blood is more likely to clot.
Surgery is a major risk factor, particularly orthopedic procedures involving the hip, knee, or leg. The combination of vein damage during surgery and reduced movement during recovery creates ideal conditions for clot formation.
Cancer increases clotting risk significantly. Many cancers release substances that promote clotting. Chemotherapy further raises this risk. People with active cancer are among the highest-risk groups for DVT and PE.
Clotting disorders, whether inherited or acquired, cause blood to coagulate more readily than normal. These include conditions like Factor V Leiden mutation, antiphospholipid syndrome, and elevated clotting factors from other causes.
Hormonal factors also raise risk. Estrogen-containing birth control pills and hormone replacement therapy increase clotting factors in the blood. Pregnancy places pressure on pelvic veins, slowing blood return from the legs. The risk remains elevated for about six weeks after delivery.
Other contributing causes include heart failure, atrial fibrillation, a prior heart attack or stroke, obesity, smoking, dehydration, and COVID-19 infection in severe cases. Learn more about coronary thrombosis and related clotting mechanisms.
Risk Factors
Key risk factors for pulmonary embolism include a personal or family history of DVT or PE, recent surgery especially involving the hip or knee, extended bed rest or travel, active cancer, inherited clotting disorders, pregnancy, use of hormonal contraceptives, obesity, smoking, age over 60, and existing cardiovascular disease.
People with atrial fibrillation carry elevated risk because blood can pool and clot inside the heart itself, and those clots can travel to the lungs. People with heart failure have slower circulation overall, which increases the likelihood of clot formation in the deep veins.
Having multiple risk factors at the same time compounds danger significantly. A person who has recently had hip replacement surgery, is overweight, and uses hormonal contraceptives faces a much higher risk than someone with only one of these factors.
At the BaleDoneen Method, assessing clotting risk through advanced cardiovascular testing and genetic testing helps identify patients who need preventive action before a clot forms.
How Is Pulmonary Embolism Diagnosed?
CT pulmonary angiography is the gold standard diagnostic test. A contrast dye is injected and a CT scanner produces detailed images of the lung arteries, showing exactly where clots are located and how much of the circulation is affected. It is fast, accurate, and widely available in emergency settings.
The D-dimer blood test measures a protein fragment released when blood clots break down. A normal D-dimer result makes PE unlikely in low-risk patients and can rule it out without further imaging. An elevated D-dimer alone does not confirm PE but signals that further imaging is needed.
An ultrasound of the leg veins looks for DVT, the source clot that may have already sent an embolism to the lungs. Finding a DVT in a patient with respiratory symptoms strongly supports a PE diagnosis even before imaging of the lungs is done.
Oxygen saturation monitoring using a pulse oximeter measures the percentage of oxygen in the blood. Normal is 95 to 100 percent. A reading below 92 percent indicates significant hypoxia and raises urgency. A rapidly falling reading is a sign the situation is deteriorating.
An echocardiogram can show right heart strain, a sign that the PE is affecting heart function. Electrocardiogram findings may show a rapid heart rate or specific patterns associated with right heart stress. A VQ scan, which uses a radioactive tracer to map airflow and blood flow in the lungs, is an alternative for patients who cannot receive CT contrast dye.
Treatment and Prevention
Treatment for pulmonary embolism must begin immediately. The goals are to stop the clot from growing, prevent new clots from forming, and restore blood flow to the affected lung tissue.
Anticoagulants, commonly called blood thinners, are the cornerstone of PE treatment. They do not dissolve the existing clot but prevent it from extending and stop new clots from forming while the body gradually breaks down the existing one. Options include injectable heparin for rapid effect in the hospital, followed by direct oral anticoagulants such as rivaroxaban or apixaban, or warfarin for longer-term management. Most patients take anticoagulants for three to six months. High-risk patients may need them indefinitely.
Thrombolytic therapy uses powerful clot-dissolving drugs to break up the blockage directly. These are used in massive PE when blood pressure has collapsed or the patient is in shock. They carry a significant bleeding risk and are reserved for the most severe cases where the benefit clearly outweighs the danger.
Catheter-directed procedures deliver clot-dissolving medication directly into the blocked artery through a tube, or use mechanical devices to break up and remove the clot. These options are used when standard blood thinners are not enough and systemic thrombolytics carry too much bleeding risk.
Surgical embolectomy physically removes the clot from the pulmonary artery. This is rare and reserved for life-threatening situations where other approaches have failed or are not possible.
An inferior vena cava filter is a small device inserted into the body’s largest vein to catch clots before they reach the lungs. It is used in patients who cannot take blood thinners safely or who continue to have PE despite anticoagulation.
Prevention is the most powerful strategy. Moving regularly during long trips, staying well hydrated, wearing compression stockings after surgery, taking prescribed blood thinners before and after high-risk procedures, and maintaining a healthy weight all reduce the risk of clot formation. Avoiding smoking and managing underlying conditions including hypertension, heart failure, and obesity lower baseline clotting risk. Learn more about heart attack prevention and stroke prevention for overlapping cardiovascular risk reduction strategies. Lifestyle approaches including anti-inflammatory nutrition and personalized exercise also support vascular health.