Pulmonary embolism (PE)

 
What is Pulmonary Embolus?

Click here for Powerpoint on imaging PE (Big file slow to load)

Pulmonary embolus is a blockage of an artery in the lungs by fat, air, tumor tissue, or blood clot.

What causes Pulmonary Embolus?

Pulmonary emboli are caused by clots from the venous circulation, from the right side of the heart, from tumors that have invaded the circulatory system, or from other sources such as amniotic fluid, air, fat, bone marrow, and foreign substances. Most are caused from clots originating in the lower extremities called deep vein thrombosis(DVT), and many resolve on their own. A pulmonary embolism affects as many as 5 out of 10,000 people in the U.S. each year, and sudden death can occur as a result of pulmonary embolism. The risk factors include prolonged bed rest or inactivity, oral contraceptive use, surgery, child birth, cancer, stroke, heart attack, heart surgery, and fractures of the hips or femur.

How can you prevent Pulmonary Embolus?

Early detection and treatment of DVT(clots of the legs) of patients who are at risk by early walking and activity after surgery can reduce the risk of pulmonary embolus. Other clot-preventive measures include leg exercises and elastic support stockings as appropriate. Subcutaneous heparin therapy (low doses of heparin injected under the skin) may be used for those on prolonged bedrest.

What are the symptoms of Pulmonary Embolus?

  • cough:
    • begins suddenly
    • may produce bloody sputum (significant amounts of visible blood or lightly blood streaked sputum)
  • sudden onset of shortness of breath at rest or with exertion
  • splinting of ribs with breathing (e.g., bending over or holding the chest)
  • lightheadedness
  • fainting
  • dizziness
  • chest pain:
    • under the breastbone or on one side
    • sharp, stabbing, burning, aching or dull, heavy sensation
    • may be worse at night
    • may radiate to the shoulder, arm, neck, jaw, or other area
    • may be worsened by breathing deeply, coughing, eating, bending, or stooping
  • sweating
  • anxiety
  • breathing, rapid
  • rapid heart rate (tachycardia)

Additional symptoms that may be associated with this disease:

  • wheezing
  • skin, clammy
  • skin discoloration, bluish
  • pulse, weak or absent
  • nasal flaring
  • joint pain
  • pelvis pain
  • leg pain in one or both legs
  • breathing, absent temporarily
  • blood pressure, low
  • abdominal indigestion
  • swelling in the legs (lower extremeties)
  • lump associated with a vein near the surface of the body (superficial vein), may be painful

Signs & Tests:

Tests to evaluate the function of the lungs:

  • arterial blood gases
  • pulmonary function tests

Tests to detect the location and extent of embolism:

  • chest X-ray
  • lung scan
  • pulmonary angiogram

Tests to detect DVT (a common cause):

  • venography of the legs
  • extremity arteriography
  • blood flow studies
  • Doppler ultrasound exam of an extremity
  • plethysmography of the legs

An ECG may show abnormalities caused by strain on the heart

This disease may also alter the results of the following tests:

  • pulmonary ventilation/perfusion scan
  • febrile/cold agglutinins
  • antithrombin III
  • ACE levels

Treatment

Emergency treatment and hospitalization are necessary. Definitive treatment consists of dissolving the clot by thrombolytic therapy. Anticoagulant therapy is preventive by inhibiting further clot formation.

Thrombolytic therapy (clot-dissolving medication) includes streptokinase, urokinase, or TPA. Anticoagulation therapy (clot-preventing medication) consists of heparin by intravenous infusion initially, then oral warfarin (Coumadin), or subcutaneous heparin may be started concurrently. Oxygen therapy is required to maintain normal oxygen concentrations until the acute injury to the lungs has resolved.

The death rate is 30% with undiagnosed pulmonary embolism. After diagnosis and treatment, the death rate drops to 3%.

 

 

Radiographic Appearance
The CXR is abnormal in the majority of cases of PE. The PIOPED study showed that among patients with angiographically proven pulmonary embolism, only 12% had chest X-rays interpreted as normal. (24% of patients with PE in another study had normal CXR's ). Atelectasis and other focal pulmonary parenchymal abnormalities are the most common CXR findings in pulmonary embolism, occurring in up to 68% of patients with PE. Pleural effusions are also common but usually small and unilateral. Other palin film findings indicative of PE include regional oligemia (Westermark sign),
Westermark sign – Dilatation of pulmonary vessels proximal to embolism along with collapse of distal vessels, often with a sharp cut of

f c/o Dr Jpyosh Kumar TGH


Hampton's hump a pleural-based wedge shaped area of increased opacity ,
Knuckle signprominence of the central pulmonary artery with abrupt tapering.

In pulmonary angiography,an embolus classiclally produces a filling defect within the affected pulmonary artery. Non-occlusive emboli have a "tram-track" appearance. Although considered the gold standard, angiography may not always detect the presence of emboli. Some indirect angiographic evidence for the presence of emboli such as vascular pruning and delayed capillary blush are non-specific. Additionally, agreement among angiographers regarding the presence of subsegmental emboli is poor and can be as low as 15%. V/Q scans can provide a road map to angiography, but if the abnormally perfused segment on the V/Q scan appears normal at angiography, complete evaluation the remainder of the lungs for the presence of pulmonary emboli is warranted. One important point to remember is that a negative angiogram has been shown to be an excellent indicator of a good prognosis.

Helical CT is able to identify main, lobar, and segmental emboli with a reported sensitivity over 90%. Although the detection of subsegmental emboli is worse, the clinical significance of these small emboli has not yet been establishished. Additionally, on angiography there is poor interobserver agreement for the presence of subsegmental emboli and the true incidence of isolated subsegmental emboli is difficult to determine. Helical CT has also been shown to have a significantly better sensitivity, specificity, positive, and negative predictive values compared to V/Q scanning . Helical CT permits a more confident diagnosis to be made in a greater number of cases when compared with V/Q scanning .

It has been suggested that helical or electron beam CT should be the initial imaging modality to screen patients suspected of having PE- particularly in patients with abnormal CXR's in whom there is a greater likelihood of inconclusive V/Q scan results. If emboli are detected, no further work-up is required. If this study is negative, a lower extremity US or CT DVT exam can be performed to assess for the presence of DVT. Again, a positive exam would lead to patient treatment. If both studies were negative, then a decision would be required regarding whether the patient should proceed to angiography or not. Another benefit of CT is the ability to suggest an alternative diagnosisDefinition
 
Pathology

 3rd most common cause of death.
2nd most common cause of unexpected death in most age groups.
60% of patients dying in the hospital have had a PE.
Diagnosis has been missed in about 70% of the cases


 Pulmonary embolism (PE) can be associated with significant mortality if untreated. The clinical diagnosis of pulmonary embolism is unreliable. Symptoms of PE include tachypnea/dyspnea (most common), tachycardia, hypoxia, pleuritic chest pain, hemoptysis, syncope, and atrial fibrillation. Blood gas may be normal.

The D-dimer blood test is a screening tool for pulmonary embolism. A serum level less than 500 ng/L excludes pulmonary embolism with a 90% accuracy. A positive test is non-specific. Additionally, the test is unreliable in the presence of malignancy, sepsis, recent surgery, or trauma.

The source is most commonly from deep venous thrombosis in the lower extremity, however, about 10% arise from clot in the upper extremity. Risk factors are Immobilization, Recent Surgery, Underlying Malignancy, History of Deep Venous Thrombosis or Pulmonary Embolism, Estrogen use, or Pre-existing cardiac disease. A low percentage of cases of pulmonary embolism result in pulmonary infarction, due to the presence of the bronchial circulation.
 
Treatment:
Treatment for PE most commonly consists of anticoagulation with heparin or coumadin. Anticoagulation prevents clot propagation and allows endogenous fibrinolytic activity to dissolve existing thrombiAnticoagulation decreases mortality form 30-60% to <5%.
Thrombolytic agents are not routinely used for the treatment of acute PE. Thrombolytic treatment is generally reserved for patients with massive pulmonary embolism producing circulatory shock (hypotension).

For patients that cannot be anticoagulated, an inferior vena caval filter can be placed in order to prevent life-threatening PE. Major complications occur in about 1% of cases. Complications include central migration of the filter, filter fracture, inferior vena caval perforation, and vena caval thrombosis.
V/Q scanning has been the mainstay for screening symptomatic patients for the presence of pulmonary embolism. A negative V/Q scan essentially excludes PE, and a high probability study is associated with the presence of a PE in about 85% of cases at angiography. Confusion arises with low or intermediate probability examinations, and there is common disagreement among expert readers in the interpretation of scans in these categories. The problem with V/Q scanning is that it does not directly visualize thromboembolism, but rather its effects on perfusion and ventilation . This problem causes the need for probability criteria, which in turn causes confusing results. Nuclear medicine scanning for PE is probably most useful in previously healthy patients with a normal chest radiograph. As the complexity of the patients underlying cardiopulmonary disease increases, so does the likelihood that the scan will not be informative (intermediate probability). Using PIOPED criteria, intermediate probability V/Q scans occurred in 60% of patients with COPD, but in only 13% of patients with normal CXR's. However, a generalized abnormality on CXR such as diffuse pulmonary edema or reticulonodular disease may not cause the perfusion lung scan to be abnormal.
 
Images

Ventilation perfusion scan showing perfusion defect in right side + coressponding ventilation defect

CXR shows RLL collapse

 

Contrast CT showing embolus

Emboli in Pulmonary Angiogram

 

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