In this post, let’s understand about this silent killer – Pulmonary embolism. In simple terms, it means ‘Clot in arteries of the lung’.
What is a Pulmonary Embolism (PE)?
A pulmonary embolism (PE) occurs when a blood clot (thrombus) becomes lodged in an artery in your lung, blocking blood flow to that part of the lung. It is not a disease in itself but rather a complication of an underlying blood clot (venous thrombosis). Most commonly, these clots originate in the deep veins of your lower legs (calf veins), often in venous valve pockets or other areas of slow blood flow. These clots then travel through the right side of your heart to reach your lungs.
What causes a PE?
PE usually arises from a deep vein thrombosis (DVT), primarily from the lower extremities. DVT and PE are usually interrelated and therefore a common word ‘Venous Thrombo-embolism (VTE)’ is used as well to refer to these conditions. The formation of blood clots that lead to PE is influenced by three main factors, known as Virchow’s triad:
- Injury to the inner lining of blood vessels (endothelial injury).
- Slow or turbulent blood flow (stasis or turbulence), which can occur with immobility, such as prolonged bed rest or long-distance travel, or in conditions like heart failure.
- Increased tendency for blood to clot (blood hypercoagulability), which can be due to various medical conditions, obesity, trauma, surgery, or inherited clotting disorders.
Risk factors for the development of VTE
- Immobilization, especially due to surgery or prolonged bed rest.
- Recent surgery or trauma, particularly leg amputations, hip, pelvic, or spinal surgery, and fractures of the femur or tibia.
- Cancer (malignancy), which has been identified in 17% of patients with venous thromboembolism.
- Pregnancy and the postpartum period, during which the incidence of thromboembolic disease is increased.
- Use of oral contraceptives or estrogen replacement therapy.
- Hereditary factors that increase clotting risk, such as Factor V Leiden mutation (the most common genetic risk factor) or deficiencies in natural blood thinners like protein C, protein S, and antithrombin III.
- Acute medical illnesses like congestive heart failure (CHF) or myocardial infarction (heart attack).
- Smoking.
- A previous history of PE or deep vein thrombosis (DVT).
- Central venous instrumentation (e.g., central lines), especially in children.
What are the signs and symptoms of a PE?
The classic presentation of PE is the abrupt onset of pleuritic chest pain (pain that worsens with breathing), shortness of breath (dyspnea), and low oxygen levels (hypoxia). However, it is important to know that most patients with pulmonary embolism have no obvious symptoms at presentation. Symptoms can vary widely, from sudden, catastrophic collapse to gradually worsening shortness of breath.
Other possible atypical symptoms and common physical signs include:
- Rapid breathing (tachypnea).
- Rapid heart rate (tachycardia).
- Fever.
- Productive cough (sometimes with blood, called hemoptysis).
- Wheezing.
- Syncope (fainting) or a decreased level of consciousness.
- Abdominal pain or flank pain.
- Swelling in the lower extremities or other signs of thrombophlebitis.
If you experience unexplained respiratory symptoms, PE should be suspected.
How is a PE diagnosed?
Diagnosing PE involves a careful assessment of your symptoms, medical history, and risk factors. Your doctor may use clinical scoring systems to estimate the likelihood of PE.
Common diagnostic tests include:
- D-dimer test: This blood test can help rule out PE, especially if your clinical risk is low. A low D-dimer level often means further investigation is unnecessary. However, this test is not as helpful in high-risk patients, as further investigation is mandatory even if the result is normal.
- Computed Tomography Pulmonary Angiography (CTPA): This is considered the first-line and primary test for diagnosing PE. It uses X-rays and a contrast dye to create detailed images of your lung arteries to detect clots.
- Ventilation-Perfusion (V/Q) Scan: This scan is often used if CT scanning is not available or is not suitable for you (e.g., due to kidney problems or allergies to the contrast dye).
- Ultrasound of your leg veins (Duplex Ultrasonography or Colour Doppler ultrasound): Since most PEs originate from clots in the legs, this non-invasive test can help find deep vein clots there.
- Electrocardiogram (ECG): While often normal in PE, it can show signs of heart strain or help rule out other heart conditions like a heart attack.
- Echocardiography: This ultrasound of the heart can help assess the heart’s function, especially the right side, and may sometimes identify clots that are traveling to the lungs.
Routine laboratory tests are generally not specific for PE but may suggest other diagnoses.
How is a PE treated?
Prompt recognition and treatment are potentially life-saving. The primary treatment for PE is anticoagulation (blood thinners), which is started immediately if PE is suspected, even before a definitive diagnosis is confirmed. It is crucial that diagnostic investigations do not delay this initial therapy.
Key treatment approaches include:
- Anticoagulation Medications: These medications help prevent existing clots from growing larger and new clots from forming. Common examples include unfractionated heparin, low-molecular-weight heparin, Factor Xa inhibitors, fondaparinux, and warfarin. Long-term anticoagulation is critical to prevent recurrence, often recommended for 3-6 months.
- Thrombolytic Therapy (Clot Busters): These powerful medications are used in more severe cases, particularly if you have very low blood pressure (hypotension) and are in cardiogenic shock, or if your clinical condition suggests a high risk of developing severe complications. They work by dissolving the blood clots.
- Surgical Options: In selected cases, surgical interventions may be considered. These can include catheter-directed thrombolysis (delivering clot-dissolving medication directly to the clot), surgical embolectomy (surgical removal of the clot), or the placement of vena cava filters (devices placed in a large vein to catch clots before they reach the lungs). Vena cava filters are generally reserved for patients who cannot receive anticoagulation or who experience recurrent clots despite adequate treatment.
- General Supportive Measures: If your oxygen levels are low, you may receive oxygen therapy. Intravenous fluids may be given if you are in circulatory shock.
What is the prognosis for PE, and what is the risk of recurrence?
The outcome for patients with PE depends on how quickly the condition is diagnosed and treated, as well as any underlying health conditions.
- Mortality: According to the CDC, approximately 25% of individuals with a PE may experience sudden death if untreated. However, anticoagulant treatment significantly decreases the mortality rate to less than 5%. The risk of death varies based on the severity of the PE, with high-risk PE (associated with low blood pressure) having a significantly higher mortality rate than intermediate or low-risk cases.
- Resolution: With appropriate treatment, many lung scan defects caused by the clots resolve over time, with about 73% resolved within 3 months. Most patients treated with anticoagulants do not develop long-term complications.
Recurrence: The risk of recurrent PE is highest in the first 6-12 months after the initial event. About one-third of individuals may experience another embolic event within 10 years. This risk of recurrence highlights why long-term anticoagulation is critical. In a small percentage of patients, the PE may not fully resolve, leading to chronic pulmonary hypertension.
What should I do to manage my PE and prevent future clots?
- Adhere to your treatment plan: It is critically important to take your medications exactly as prescribed by your doctor to prevent the recurrence of blood clots.
- Monitor for bleeding: Since blood thinners increase your risk of bleeding, your healthcare provider will instruct you on what to do in the event of any bleeding complications and when to seek medical attention.
- Be aware of drug interactions: If you are taking anticoagulants like warfarin or low-molecular-weight heparin, discuss all other medications, supplements, and even certain foods with your doctor or pharmacist, as they can interact with your blood thinners.
- Understand your risk factors: Being aware of your personal risk factors for PE can help you and your healthcare team manage your condition and take steps to reduce the likelihood of future events.