Pulmonary embolism (PE) is a life-threatening medical condition characterized by the sudden blockage of one or more arteries in the lungs.
This occurs when a blood clot, usually originating in the legs, travels through the bloodstream and lodges in the pulmonary arteries.
PE can have severe consequences, including shortness of breath, chest pain, and, in some cases, fatal outcomes.
In this article, we will explore the causes, symptoms, diagnosis, and treatment options for pulmonary embolism, shedding light on the critical importance of early detection and intervention.
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What is a Pulmonary Embolism?
A pulmonary embolism is a medical emergency in which a blood clot, typically originating in the legs, travels through the bloodstream and blocks one or more arteries in the lungs. This sudden obstruction can lead to symptoms like chest pain and shortness of breath and, in severe cases, can be fatal if not promptly diagnosed and treated.
Signs and Symptoms
The signs and symptoms of a pulmonary embolism can vary greatly depending on the size of the clot, how much of the lung is involved, and the individual’s overall health.
Common symptoms include:
- Shortness of breath
- Chest pain
- Lightheadedness or dizziness
- Excessive sweating
- Swelling in the legs or ankles
Note: Severe cases may present with symptoms of shock, such as a severe drop in blood pressure, rapid and weak pulse, and loss of consciousness. Immediate medical attention is crucial if a pulmonary embolism is suspected.
The diagnosis of a pulmonary embolism is often challenging due to its nonspecific signs and symptoms.
However, a combination of clinical assessment, imaging, and laboratory tests can help establish the diagnosis:
- Clinical Assessment: Initial evaluation with a detailed history and physical examination to assess the probability of PE and identify risk factors such as recent surgery, immobilization, or a history of deep vein thrombosis (DVT).
- D-dimer Test: A blood test that measures a substance that’s released when a blood clot breaks up. High levels of D-dimer may suggest the presence of an acute PE, but this test is not specific and can be elevated in other conditions.
- Computed Tomography Pulmonary Angiography (CTPA): Currently the gold standard for the diagnosis of PE, CTPA can directly visualize the clot within the pulmonary arteries.
- Ventilation-Perfusion Scan (V/Q Scan): Used if the patient cannot undergo CTPA due to allergy to contrast material or kidney disease. It detects areas of the lung that are ventilated but not perfused by blood flow.
- Ultrasound of the Legs: To detect clots in the deep veins of the legs (DVT), which can travel to the lungs and cause PE.
- Pulmonary Angiogram: An invasive test that involves guiding a catheter through the veins into the pulmonary artery. It’s rarely performed now due to the accuracy of CTPA.
- Echocardiogram: May be used to look for signs of strain on the right side of the heart, which can suggest the presence of PE.
- Chest X-ray: While it cannot diagnose PE, it can rule out other conditions that may mimic PE.
- MRI: Can be used as an alternative to CTPA in certain patients, such as pregnant women.
- Blood Tests: To check for conditions that might predispose to clotting (coagulation studies), and to assess the function of the heart and lungs.
Note: In some cases, the diagnosis is made on clinical grounds when imaging is not possible, especially if the patient is hemodynamically unstable. Prompt diagnosis and treatment are vital to reduce the risk of mortality associated with PE.
The treatment for a pulmonary embolism is aimed at preventing further clot formation, dissolving existing clots, and managing symptoms.
The approach varies depending on the severity of the condition:
- Anticoagulation: The mainstay of PE treatment is anticoagulant therapy, which prevents new clots from forming and stops existing ones from growing. Initial treatment often starts with parenteral anticoagulants like heparin, which can be given intravenously or subcutaneously. This is often followed by oral anticoagulants such as warfarin, dabigatran, rivaroxaban, apixaban, or edoxaban for longer-term management.
- Thrombolytic Therapy: In cases of severe PE with hemodynamic instability (e.g., low blood pressure), thrombolytic (or “clot-busting”) drugs may be administered to rapidly dissolve the clot. However, these agents carry a significant risk of bleeding and are used selectively.
- Inferior Vena Cava (IVC) Filters: If anticoagulation is contraindicated (for example, due to bleeding risks) or ineffective, an IVC filter may be placed. This device is inserted into the inferior vena cava to catch and stop clots from traveling to the lungs from the lower limbs.
- Pulmonary Embolectomy: A surgical option for life-threatening PE or when thrombolytic therapy is contraindicated or has failed. It involves the physical removal of the clot from the pulmonary artery but is a high-risk procedure.
- Catheter-directed treatments: These minimally invasive procedures involve threading a catheter to the site of the clot, where drugs or devices can break up or remove the clot.
- Oxygen and Supportive Care: Supplemental oxygen is provided to maintain adequate oxygen levels, and in severe cases, mechanical ventilation may be required. Supportive care also includes pain management and the treatment of any underlying conditions.
- Prevention and Rehabilitation: After initial treatment, long-term measures include the prevention of deep vein thrombosis (DVT) with compression stockings, lifestyle modifications, and possibly extended anticoagulant therapy, depending on the individual risk of recurrence.
The treatment duration and strategies are personalized, depending on factors such as the size and location of the PE, patient risk factors for bleeding, and the patient’s response to treatment.
Regular follow-up is crucial to monitor the therapeutic response and to adjust anticoagulant dosing.
Pulmonary Embolism Practice Questions
1. What is a pulmonary embolism characterized by?
A pulmonary embolism is characterized by the blockage of one or more arteries in the lungs by a blood clot, which usually originates from a deep vein thrombosis (DVT) in the legs or pelvis.
2. What does PE stand for?
3. What are the most common emboli?
Thrombi from femoral veins
4. Apart from thrombi, what else can embolize into the pulmonary arteries?
Tumors, fat from bone fractures, amniotic fluid, and foreign materials.
5. What factors can cause alterations in blood flow, increasing the risk of deep vein thrombosis?
Immobilization (e.g., surgery, injury, or pregnancy), obesity, and cancer.
6. What factors can increase the coagulability of the blood?
Genetic thrombophilia, antiphospholipid syndrome, nephrotic syndrome, and cancer.
7. What is the name of the score for predicting PE?
8. What happens in the lung after a PE blocks the pulmonary artery?
Lung tissue is ventilated but not perfused, and the non-perfused area stops producing surfactant, so its alveoli collapse, exacerbating hypoxia.
9. What can happen to the heart during a pulmonary embolism?
It can undergo ischemia and systemic hypoxia, and reduced accessible pulmonary circulation causes an increase in pulmonary artery pressure and, thus, reduced cardiac output.
10. What is the difference between a small or medium PE and a massive PE?
Small or medium PEs affect a terminal pulmonary vessel, while a massive PE affects a large pulmonary vessel, even the pulmonary artery itself.
11. What are the symptoms of a small or medium PE?
Dyspnea, tachypnea, pleuritic chest pain, cough, and hemoptysis.
12. What are the symptoms of a massive PE?
Severe central chest pain, shock, paleness and sweating, cyanosis, collapse, circulatory instability, and sudden death.
13. How can a pulmonary embolism be investigated?
Chest x-ray, ECG, blood tests, and ABG.
14. How is a pulmonary embolism managed?
High-flow oxygen, analgesia, IV fluids, and fibrinolytic therapy with IV streptokinase.
15. How can a pulmonary embolism be prevented in at-risk patients?
Prevention of pulmonary embolism in at-risk patients typically involves using anticoagulants to inhibit clot formation and employing compression stockings to promote circulation, especially when immobilized, alongside lifestyle changes like regular exercise and hydration.
16. What are the causes of a pulmonary embolism?
Dehydration, venous stasis from prolonged immobility or surgery, birth control pills, clotting disorders, and heart arrhythmias (e.g., AFib).
17. Where do 95% of pulmonary emboli come from?
Veins in legs (i.e., DVT)
18. What is a D-dimer test?
A D-dimer test is a blood test that measures the presence of fibrin degradation products, which are typically found in the blood after a blood clot is broken down by the body.
19. What does an increased D-dimer mean?
Elevated D-dimer levels can indicate recent or ongoing blood clot formation and breakdown in the body, and the test is often used to rule out conditions like pulmonary embolism or deep vein thrombosis. However, a high D-dimer level is not specific to these conditions and can be elevated in other situations such as inflammation, pregnancy, or recent surgery.
20. What is a VQ scan?
A VQ scan, or ventilation-perfusion scan, is a medical imaging test that uses a radioactive material to examine airflow (ventilation) and blood flow (perfusion) in the lungs.
21. What does a VQ scan look at?
It looks at the blood flow to the lungs.
22. When may a CT or CT angiography be needed to diagnose a pulmonary embolism?
If inconclusive VQ scan or D-dimer cannot be used.
23. Why does pulse rate increase during a pulmonary embolism?
24. What promotes clotting in the veins?
Virchow’s triad: stasis, hypercoagulability, and venous injury.
25. Why does a pulmonary embolism lead to hypoxemia?
Blood that cannot get to the alveoli due to an occlusion must go somewhere else; this increases the perfusion in the new area and makes a low VQ mismatch, which is shunting that lowers O2 content.
26. How do emboli prevent gas exchange?
They block circulation to certain parts of the lung, causing no gas exchange in that area.
27. What are the risk factors for a pulmonary embolism?
Venous blood stasis, increased coagulation, and damage to the vessel wall.
28. What are other types of thrombi?
Venous, air embolus, fat embolus, septic embolus, and tumor.
29. What is the pathophysiology of a pulmonary embolism?
The pathophysiology of pulmonary embolism centers on blood clots blocking pulmonary arteries, impairing lung blood flow and gas exchange, increasing pressure on the heart’s right ventricle, and potentially leading to lung tissue death and right heart failure.
30. Why do clots tend to form at the bottom of the lung?
Because there is decreased perfusion in that region.
31. What causes an increase in ventilation?
An increase in dead space.
32. What does occlusion of blood flow lead to?
Increased pulmonary vascular resistance, which causes the redistribution of blood flow and pulmonary shunting, and blood returns to systemic circulation with inadequate O2.
33. What can a large embolus lead to?
Hemodynamic collapse, causing decreased cardiac output.
34. What is the treatment for an acute pulmonary embolism?
IV heparin to prolong the clotting time.
35. What is the treatment for a long-term pulmonary embolism?
36. What are the EKG findings for a possible pulmonary embolism?
Tachycardia, right axis deviation, inverted T waves, and right bundle branch block.
37. What are the consequences of a pulmonary embolism?
Right-sided heart strain, complete resolution, infarction, recurrent emboli, pulmonary hypertension because of the chronic strain on the heart, and death.
38. When should contrast not be used during a CT angiogram?
Kidney failure or allergies.
39. What can be noted in a D-dimer test?
It shows increased thrombolytic activity in the body. This test is often done in the ER and may show false positives, but is helpful if negative.
40. What are the medications for a pulmonary embolism?
Heparin, synthetic pentasaccharide, coumadin, warfarin, and thrombolytics.
41. What condition is CT angiogram not helpful during diagnosis?
Small peripheral emboli.
42. What are the strong risk factors for a pulmonary embolism?
Fracture to a lower limb, hospitalization with AF or heart failure, THR, major trauma, myocardial infarction in the past 3 months, and previous DVT.
43. What are the moderate risk factors for a pulmonary embolism?
Autoimmune disease, blood transfusion, paralytic stroke, and infection.
44. What scoring system is used to determine the likelihood of a PE?
45. What would be the presentation of a massive PE?
A patient presents with sudden severe chest pain, shortness of breath, and syncope. They are hypertensive with raised JVP and have the S1Q3T3 pattern on an ECG.
46. What initial tests should be performed for a suspected PE?
Chest x-ray, ECG, ABG, D-dimer, and CT pulmonary angiogram.
47. What is the best test for diagnosing a pulmonary embolism?
CTPA is the gold standard
48. What additional tests may be done after a pulmonary embolism diagnosis for prognostic purposes?
Echocardiogram looking for right ventricular dysfunction and troponin looking for signs of cardiac damage; both are associated with a higher risk for early mortality.
49. What is an alternative approach to treating a PE that does not involve regular blood testing?
Immediately start apixaban or rivaroxaban and stay on them long term.
50. For how long should warfarin be continued after a PE?
At least 3 months, then reassess if there is a need for continued use.
51. What is a thrombus?
A blood clot that forms and remains in a vein.
52. What is the definition of an embolus?
A blood clot that becomes dislodged and travels to another part of the body.
53. What is a pulmonary infarction?
When the tissue of the lung dies.
54. Besides clots, what are some possible causes of a pulmonary embolism?
Fat, air, amniotic fluid, bone marrow, and tumor fragments.
55. What are three things that can cause blood clot formation?
Increased tendency of blood to form clots, injury to the endothelial cells that line the vessels, and slowing or stagnation of blood flow through the veins.
56. What term describes the increased tendency of blood to form clots?
57. What clotting factors in the blood might increase and cause a clot?
Prothrombin and polycythemia
58. What is a natural anticoagulant that may cause clotting if it is deficient?
59. How does the slowing of blood flow make clots more likely to form?
It allows platelets more time in contact with the endothelium.
60. What can cause venous stasis?
Inactivity, CHF, varicose veins, and thrombophlebitis.
61. How does a chest x-ray help diagnose a pulmonary embolism?
It is often normal but can be used to rule out conditions with the same symptoms.
62. What does a D-dimer test look for, and what is considered positive results?
It tests for protein fibrinogen, and values higher than 500 ng/mL are positive.
63. What test is used to differentiate between blood and clots?
Magnetic resonance angiography (MRA)
64. What results from venous admixture developing in a pulmonary embolism?
It causes bronchial smooth muscle constriction.
65. What is the effect of a pulmonary embolism on venous admixture?
It causes increased venous admixture.
66. What is abnormal about heart sounds with PE patients?
Increased S2 due to the valve closing more forcefully, increased splitting of S2, and a third heart sound.
67. What portion of the heart works harder when there is increased pressure in the lungs?
68. What is the most common abnormal ECG pattern that may suggest the possibility of a PE?
69. What are some possible x-ray findings in a patient with a PE?
Increased density, hyper radiolucency distal to the embolus, dilation of pulmonary arteries, pulmonary edema, cor pulmonale, and pleural effusion.
70. What diagnostic imaging procedure uses a radioactive compound that is inhaled into the lungs?
71. What is heparin?
A fast-acting anticoagulant.
72. What is the name of a slow-acting, oral anticoagulant that can be taken preventatively at home?
Warfarin (i.e., Coumadin, Panwarfin)
73. What do thrombolytic agents do?
They actually dissolve the clot.
74. What thrombolytic agents can dissolve clots?
Streptokinase, urokinase, alteplase, and reteplase.
75. What are some preventative measures that can be taken to avoid a pulmonary embolism?
Early ambulation, walking, exercise, drinking fluids, compression stockings, vein filters, and pneumatic compression.
76. What is a pulmonary embolectomy?
The surgical removal of clots in the lungs.
77. Can a pulmonary embolism result in death?
Yes, it is fatal in one-third of patients who are undiagnosed and untreated.
78. What are the breathing patterns for a pulmonary embolism?
Dyspnea and tachypnea
79. What are three diagnostic tests for a pulmonary embolism?
V/Q scan, angiography, and ABG.
80. What types of medications can be administered to treat a pulmonary embolism?
Anticoagulants, thrombolytic agents, analgesics, and inotropic agents.
Pulmonary embolism is a serious medical condition that requires prompt medical attention and intervention. Its potentially fatal consequences highlight the significance of recognizing its symptoms and risk factors.
While advancements in medical knowledge and technology have improved our ability to diagnose and treat PE, prevention remains crucial.
Maintaining a healthy lifestyle and managing risk factors, such as immobility and certain medical conditions, can reduce the likelihood of experiencing this life-threatening condition.
John Landry is a registered respiratory therapist from Memphis, TN, and has a bachelor's degree in kinesiology. He enjoys using evidence-based research to help others breathe easier and live a healthier life.
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