Pulmonary Embolism: Symptoms, Causes & Emergency Warning Signs

What Is Pulmonary Embolism?

Pulmonary embolism (PE) is a blockage in one or more arteries in the lungs, usually caused by blood clots that travel from the deep veins of the legs to the lungs. It is the third most common cardiovascular cause of death after heart attack and stroke, affecting approximately 1-2 per 1,000 people annually worldwide.

Pulmonary embolism occurs when a blood clot, most commonly originating from the deep veins of the legs or pelvis (a condition called deep vein thrombosis or DVT), breaks loose and travels through the bloodstream to the lungs. When the clot reaches the pulmonary arteries, it blocks blood flow to part of the lung, which can be life-threatening if not treated promptly.

The severity of pulmonary embolism depends on the size and number of clots, and whether the patient has underlying heart or lung disease. A massive PE involving large central arteries can cause sudden cardiovascular collapse and death within minutes to hours. Smaller emboli may cause less dramatic symptoms but can still lead to long-term complications if not treated appropriately.

Understanding the pathophysiology helps explain why PE is so dangerous. When blood flow to a portion of the lung is blocked, that area cannot participate in gas exchange, leading to low oxygen levels in the blood. Additionally, the blocked artery creates back-pressure on the right side of the heart, which must work harder to pump blood through the lungs. In severe cases, this right heart strain can lead to heart failure.

The Connection Between DVT and PE

Deep vein thrombosis and pulmonary embolism are together referred to as venous thromboembolism (VTE). They represent different manifestations of the same underlying disease process. Approximately 90% of pulmonary emboli originate from clots in the deep veins of the legs, though clots can also form in the pelvic veins, arm veins, or rarely in the right side of the heart.

The journey of a clot from leg to lung follows the body's venous circulation. Blood from the legs travels upward through increasingly larger veins, eventually reaching the right side of the heart. From there, it is pumped into the pulmonary arteries. A clot that breaks free can travel this entire path until it becomes lodged in a pulmonary artery too small to allow its passage.

Types of Pulmonary Embolism

Medical professionals classify PE based on severity and hemodynamic impact:

• Massive (high-risk) PE: Causes hemodynamic instability with low blood pressure, shock, or cardiac arrest. Requires immediate aggressive treatment.
• Submassive (intermediate-risk) PE: Normal blood pressure but evidence of right heart strain. May require close monitoring and potentially escalated therapy.
• Low-risk PE: Stable vital signs and no right heart strain. Can often be treated as an outpatient with anticoagulation alone.

What Are the Symptoms of a Pulmonary Embolism?

The classic symptoms of pulmonary embolism include sudden onset of shortness of breath, sharp chest pain that worsens with deep breathing (pleuritic pain), rapid heartbeat, coughing (sometimes with blood), and feeling dizzy or faint. Many patients also have symptoms of deep vein thrombosis, such as leg swelling and pain.

The symptoms of pulmonary embolism can range from subtle to dramatic, making diagnosis challenging. The presentation depends on the size and location of the clot, the patient's underlying health, and how much of the lung is affected. Some patients have warning signs days before a major event, while others experience sudden catastrophic symptoms.

Shortness of breath is the most common symptom, occurring in approximately 80% of patients with PE. Unlike the gradual breathlessness that develops with chronic lung disease, the dyspnea of PE typically comes on suddenly, often within seconds to minutes. Patients frequently describe it as feeling unable to catch their breath or as if they cannot get enough air, regardless of how deeply they breathe.

Chest pain occurs in about 50-60% of patients and has characteristic features. The pain is typically described as sharp or stabbing, located on one side of the chest, and worsens with deep breathing, coughing, or movement. This pleuritic quality distinguishes it from the crushing central chest pain of heart attack. However, in massive PE affecting central arteries, patients may experience substernal pressure similar to cardiac pain.

Additional Symptoms to Watch For

Beyond the classic triad of dyspnea, chest pain, and hemoptysis (coughing blood), patients with PE may experience a variety of other symptoms:

• Rapid or irregular heartbeat: The heart compensates for reduced oxygen by beating faster, often exceeding 100 beats per minute
• Dizziness or lightheadedness: Reduced blood flow to the brain can cause feeling faint or actually fainting (syncope)
• Anxiety or sense of doom: Many patients describe an overwhelming feeling that something is seriously wrong
• Sweating: Cold, clammy skin is common, especially with larger emboli
• Leg pain or swelling: Signs of the underlying DVT are present in about 50% of PE patients
• Low-grade fever: Some patients develop mild fever as an inflammatory response

What Causes Pulmonary Embolism?

Pulmonary embolism is caused by blood clots that typically form in the deep veins of the legs (deep vein thrombosis) and travel to the lungs. Risk factors include prolonged immobility, recent surgery, cancer, pregnancy, hormonal contraceptives, obesity, smoking, and inherited clotting disorders. The classic triad of causation includes blood stasis, vessel damage, and hypercoagulability.

Understanding the causes of pulmonary embolism requires knowledge of Virchow's triad, a concept developed in the 19th century that remains central to our understanding of blood clot formation. The three components of this triad are venous stasis (slowing of blood flow), endothelial injury (damage to the blood vessel lining), and hypercoagulability (increased tendency for blood to clot). Most cases of VTE involve one or more of these factors.

Venous stasis is perhaps the most common contributor to clot formation. When blood flows slowly through the veins, it has more time to activate clotting factors and form thrombi. This explains why prolonged immobility - whether from long-haul flights, extended bed rest after surgery, or paralysis - significantly increases PE risk. The veins of the lower legs depend on muscle contraction to push blood upward against gravity, so when the calf muscles are inactive, blood pools in the deep veins.

Endothelial injury can occur from surgery, trauma, or medical procedures. When the smooth inner lining of blood vessels is damaged, it triggers the body's clotting cascade as a protective mechanism. This is why major surgeries, particularly orthopedic procedures on the hips and knees, carry high VTE risk. The combination of surgical trauma and postoperative immobility creates a perfect storm for clot formation.

Major Risk Factors for Pulmonary Embolism

Risk factors for PE can be divided into transient (temporary) and persistent categories:

Transient risk factors include:

• Surgery: Especially orthopedic, cancer, and abdominal procedures. Risk is highest in the first 4-6 weeks post-operatively
• Immobilization: Bed rest for 3 or more days, long-distance travel (flights or car trips over 4 hours)
• Trauma: Major injuries, particularly to the legs, pelvis, or spine
• Pregnancy and postpartum: Risk increases throughout pregnancy and is highest in the 6 weeks after delivery
• Hormonal therapy: Combined oral contraceptives, hormone replacement therapy, and fertility treatments

Persistent risk factors include:

• Cancer: Both the malignancy itself and cancer treatments increase clotting risk. Some cancers, particularly pancreatic, lung, and brain tumors, carry especially high risk
• Previous VTE: Having had a DVT or PE before significantly increases the risk of recurrence
• Inherited thrombophilia: Genetic conditions like Factor V Leiden mutation, prothrombin gene mutation, and protein C or S deficiency
• Antiphospholipid syndrome: An autoimmune condition that increases clotting
• Obesity: Body mass index (BMI) over 30 is an independent risk factor
• Age: Risk increases with age, particularly after 60
• Chronic medical conditions: Heart failure, inflammatory bowel disease, and chronic kidney disease

When Should You Seek Emergency Care?

Seek emergency care immediately if you experience sudden shortness of breath, chest pain that worsens with breathing, coughing blood, fainting, or rapid heartbeat. Pulmonary embolism is a medical emergency that can be fatal within hours without treatment. Do not drive yourself - call emergency services or have someone take you to the nearest emergency department.

Recognizing when to seek care for suspected pulmonary embolism can be life-saving. Because PE symptoms can mimic many other conditions, including heart attack, pneumonia, and panic attacks, many people delay seeking help. However, the consequences of untreated PE are severe - approximately 10-30% of people with PE die within one month of diagnosis, with most deaths occurring in the first few hours.

The decision to seek emergency care should be based on the presence of typical symptoms, especially if you have known risk factors. If you have recently had surgery, been immobilized, have cancer, or are taking hormonal medications, you should have a lower threshold for seeking evaluation. Even if you are young and otherwise healthy, sudden unexplained shortness of breath warrants immediate medical attention.

Symptoms That Require Emergency Response

Call emergency services immediately if you experience:

• Sudden severe shortness of breath that cannot be explained by exertion
• Chest pain that gets worse when you breathe deeply, cough, or move
• Coughing up blood or blood-tinged sputum
• Fainting or near-fainting episodes
• Rapid or irregular heartbeat with other symptoms
• Blue discoloration of lips or fingernails (cyanosis)
• Cold, clammy, pale skin

Seek same-day medical evaluation if you have:

• Mild but persistent shortness of breath that is new
• Mild chest discomfort, especially with known risk factors
• New leg swelling or pain, especially if one-sided
• Unexplained rapid heartbeat at rest

How Is Pulmonary Embolism Diagnosed?

Pulmonary embolism is diagnosed using a combination of clinical assessment, blood tests (D-dimer), and imaging. CT pulmonary angiography (CTPA) is the gold standard imaging test. Diagnosis begins with calculating the clinical probability using scoring systems like the Wells score, followed by D-dimer testing in low-probability cases and direct imaging in higher-probability cases.

Diagnosing pulmonary embolism requires a systematic approach because the symptoms overlap with many other conditions. Emergency physicians and clinicians use validated algorithms that combine clinical assessment with laboratory tests and imaging to efficiently and accurately diagnose or exclude PE while minimizing unnecessary radiation exposure and costs.

The diagnostic process typically begins with a clinical probability assessment using standardized scoring systems. The most widely used is the Wells score, which assigns points based on clinical features such as symptoms of DVT, heart rate, recent immobilization or surgery, previous VTE, hemoptysis, and cancer. Based on the total score, patients are classified as having low, intermediate, or high probability of PE.

D-Dimer Testing

D-dimer is a protein fragment produced when blood clots dissolve. Elevated D-dimer levels indicate that clotting and fibrinolysis (clot breakdown) are occurring in the body. In patients with low to intermediate clinical probability, a negative D-dimer test effectively rules out PE, with a negative predictive value exceeding 95%.

However, D-dimer has important limitations. Levels are elevated in many other conditions, including pregnancy, cancer, infection, inflammation, recent surgery, and advanced age. This means a positive D-dimer does not confirm PE but rather indicates the need for imaging. For this reason, D-dimer is not useful in patients with high clinical probability, who should proceed directly to imaging.

CT Pulmonary Angiography (CTPA)

CTPA is the definitive imaging test for pulmonary embolism and is considered the gold standard. During this test, contrast dye is injected intravenously, and CT images are taken as the contrast flows through the pulmonary arteries. Clots appear as filling defects within the contrast-enhanced vessels.

CTPA has excellent sensitivity (83-100%) and specificity (89-97%) for PE. It can detect clots in the main, lobar, and segmental pulmonary arteries, and modern scanners can visualize subsegmental emboli as well. Additional advantages include the ability to assess for alternative diagnoses (pneumonia, pneumothorax, aortic dissection) and evaluate right heart strain.

Other Diagnostic Tests

Ventilation-perfusion (V/Q) scanning is an alternative when CTPA is contraindicated, such as in patients with severe kidney disease or contrast allergy. This nuclear medicine test compares air flow (ventilation) and blood flow (perfusion) in the lungs. A mismatch - where an area receives air but not blood - suggests PE.

Echocardiography (heart ultrasound) does not directly visualize clots in the lungs but can assess right ventricular strain, which occurs in significant PE. This is particularly useful in critically ill patients who cannot undergo CTPA and helps with risk stratification.

Compression ultrasonography of the legs can identify DVT, which is present in about 50% of PE patients. Finding DVT in a patient with respiratory symptoms supports the diagnosis and may eliminate the need for additional imaging in some cases.

How Is Pulmonary Embolism Treated?

Treatment of pulmonary embolism centers on anticoagulation (blood thinners) to prevent new clots and allow the body to dissolve existing ones. Most patients receive direct oral anticoagulants (DOACs) or low-molecular-weight heparin initially, followed by oral anticoagulants for 3-6 months or longer. Massive PE may require thrombolytics (clot-dissolving drugs) or surgical intervention.

The treatment of pulmonary embolism has evolved significantly over the past two decades, with newer medications offering improved safety and convenience. The goals of treatment are threefold: prevent the existing clot from growing larger, prevent new clots from forming, and allow the body's natural fibrinolytic system to break down the existing clot over time.

For the vast majority of patients, anticoagulation alone is sufficient. The body has an inherent ability to dissolve clots through a process called fibrinolysis, and anticoagulants work by preventing new clot formation while this natural process occurs. Most clots begin to resolve within days to weeks, though complete resolution may take months.

Anticoagulation Therapy

Direct Oral Anticoagulants (DOACs) have become the preferred treatment for most patients with PE. Medications in this class include rivaroxaban (Xarelto), apixaban (Eliquis), edoxaban (Savaysa), and dabigatran (Pradaxa). DOACs offer several advantages over traditional warfarin: they work quickly, do not require regular blood monitoring, have fewer drug and food interactions, and have lower bleeding risk.

Low-molecular-weight heparin (LMWH) such as enoxaparin (Lovenox) is given by injection and works immediately. It is often used as initial treatment before transitioning to oral medications, or as the primary treatment in cancer-associated PE, pregnancy, or when DOACs are contraindicated.

Warfarin is an older oral anticoagulant that remains an option, particularly when DOACs are contraindicated or cost-prohibitive. Warfarin requires regular blood testing (INR monitoring) and careful attention to diet and drug interactions. It must be started alongside heparin or LMWH because it takes several days to become effective.

Treatment Duration

How long anticoagulation continues depends on the circumstances surrounding the PE:

• Provoked PE (clear trigger like surgery): Typically 3 months of treatment
• First unprovoked PE: At least 3-6 months, with consideration of extended therapy
• Recurrent VTE: Often indefinite anticoagulation
• Active cancer: Treatment continues as long as cancer is active or being treated
• Persistent risk factors: May require extended or indefinite treatment

Treatment for Massive Pulmonary Embolism

Patients with massive or high-risk PE - characterized by hemodynamic instability (low blood pressure, shock, or cardiac arrest) - require more aggressive treatment:

Systemic thrombolysis uses clot-dissolving medications (tissue plasminogen activator or tPA) given intravenously to rapidly break down the clot. While effective, thrombolysis carries significant bleeding risk, including approximately 2% risk of intracranial hemorrhage. It is reserved for life-threatening PE where the benefit outweighs the risk.

Catheter-directed therapy involves threading a catheter through the blood vessels to the clot, where clot-dissolving medication can be delivered locally at lower doses, or the clot can be mechanically disrupted or aspirated. This approach may offer the benefits of thrombolysis with reduced bleeding risk.

Surgical embolectomy is a major open-heart surgery to physically remove the clot from the pulmonary arteries. It is considered when thrombolysis is contraindicated or has failed, and catheter-directed therapy is unavailable.

Inferior Vena Cava (IVC) Filters

IVC filters are small metal devices placed in the main vein returning blood from the legs to the heart. They are designed to catch clots and prevent them from reaching the lungs. IVC filters are considered only when anticoagulation is absolutely contraindicated (such as active bleeding) or when PE recurs despite adequate anticoagulation. Retrievable filters should be removed once anticoagulation can be safely resumed.

How Can Pulmonary Embolism Be Prevented?

Prevention of pulmonary embolism focuses on addressing risk factors: staying active during long travel, using compression stockings when indicated, receiving prophylactic anticoagulation after surgery, avoiding prolonged immobility, maintaining healthy weight, and discussing alternative contraception options if you have clotting risk factors. Early mobilization after surgery and illness is crucial.

Preventing pulmonary embolism is far better than treating it, and many cases are preventable with appropriate measures. Prevention strategies fall into two categories: lifestyle and behavioral modifications for the general population, and medical prophylaxis for high-risk individuals.

For the general population, staying physically active is the most important preventive measure. Regular movement keeps blood flowing through the veins and prevents stasis. This is particularly important during situations that involve prolonged sitting or bed rest.

Prevention During Travel

Long-distance travel, particularly flights lasting more than 4-6 hours, increases VTE risk. The combination of immobility, dehydration, and low cabin pressure creates conditions favorable for clot formation. To reduce risk:

• Walk around the cabin every 1-2 hours when possible
• Perform seated exercises: ankle circles, calf raises, knee lifts
• Stay hydrated by drinking water regularly and limiting alcohol and caffeine
• Wear loose, comfortable clothing that does not restrict circulation
• Consider wearing graduated compression stockings, especially if you have additional risk factors
• Choose an aisle seat for easier movement

Medical Prevention (Thromboprophylaxis)

For hospitalized patients and those undergoing surgery, medical prophylaxis dramatically reduces VTE risk. Measures include:

Pharmacological prophylaxis: Low-dose anticoagulants (such as enoxaparin or low-dose heparin) given before and after surgery in high-risk procedures. The duration depends on the surgery type and patient risk factors.

Mechanical prophylaxis: Graduated compression stockings and intermittent pneumatic compression devices squeeze the legs periodically, mimicking the muscle pump that normally moves venous blood. These are particularly important when anticoagulants are contraindicated.

Early mobilization: Getting patients out of bed and walking as soon as safely possible after surgery or during illness is one of the most effective prevention strategies.

Prevention for High-Risk Groups

Certain individuals require special attention to VTE prevention:

• Cancer patients: May need prophylactic anticoagulation during hospitalization and sometimes during outpatient chemotherapy
• Pregnancy: Women with previous VTE or thrombophilia may need prophylactic anticoagulation throughout pregnancy and postpartum
• Hormonal contraception: Women with clotting risk factors should discuss alternative contraceptive methods with their healthcare provider
• Extended immobilization: Those with leg casts, prolonged bed rest, or paralysis often require prophylaxis

What Is Recovery Like After Pulmonary Embolism?

Recovery from pulmonary embolism varies from weeks to months. Most people recover fully with proper treatment, though some experience persistent symptoms called post-PE syndrome. Recovery involves continuing anticoagulation as prescribed, gradual return to physical activity, monitoring for complications, and follow-up appointments to assess resolution and determine treatment duration.

The recovery journey after pulmonary embolism is highly individual, depending on the size and location of the clot, the patient's overall health, and whether complications develop. While many patients feel significantly better within days to weeks, complete recovery of exercise tolerance and quality of life may take several months.

In the acute phase, patients often experience fatigue and may have persistent shortness of breath with exertion. This is normal and typically improves gradually as the clots dissolve and the heart and lungs heal. However, pushing too hard too quickly can be counterproductive, and patients should follow their healthcare provider's guidance on activity levels.

Post-Pulmonary Embolism Syndrome

Some patients continue to experience symptoms long after the acute event, a condition known as post-PE syndrome. Symptoms may include persistent shortness of breath, reduced exercise capacity, fatigue, and chest discomfort. This occurs in approximately 20-50% of PE survivors and can significantly impact quality of life.

Post-PE syndrome has multiple potential causes, including incomplete clot resolution, deconditioning from prolonged inactivity, anxiety about recurrence, and psychological effects of the traumatic experience. A rehabilitation program combining exercise training, education, and psychological support can help many patients improve.

Chronic Thromboembolic Pulmonary Hypertension (CTEPH)

CTEPH is a serious long-term complication that develops in approximately 2-4% of PE survivors. It occurs when organized clot material remains in the pulmonary arteries, causing persistent obstruction and elevated blood pressure in the lungs. CTEPH can develop months to years after the initial PE.

Symptoms include progressive shortness of breath, reduced exercise tolerance, and eventually right heart failure. If CTEPH is suspected, specialized testing including echocardiography, V/Q scanning, and right heart catheterization is required. Treatment options include surgical thromboendarterectomy, balloon pulmonary angioplasty, and medications to lower pulmonary blood pressure.

Follow-Up Care

Appropriate follow-up is essential for optimal recovery:

• Regular medical appointments: To assess symptom resolution, monitor for complications, and adjust medications
• Imaging follow-up: Some patients may need repeat imaging to ensure clot resolution
• Assessment at 3-6 months: To determine if anticoagulation should continue or can be stopped
• Evaluation for underlying causes: Especially for unprovoked PE, testing for cancer or thrombophilia may be appropriate
• Long-term monitoring: Especially for symptoms of CTEPH, which can develop years later