Diseases

Embolus, Pulmonary (Pulmonary Embolism) Information

Anticoagulation

Anticoagulation prevents further growth of the blood clot, preventing more lung tissue from being affected. The body has complex mechanism to form blood clots to help repair blood vessel damage. Under normal conditions, there is a clotting cascade with numerous blood factors that have to be activated for a clot to form. Under normal conditions, the body also will activate the system that breaks down clots often completed over a 4 to 6 week period. There is a careful balance between the clotting system and the system that breaks down a clot. This system is essential to help us handle bleeding injuries. When bleeding occurs, say from trauma, or a cut, this activates the clotting system to prevent major loss of blood. Medications are available that block the clotting cascade at different places and therefore "thin" or anti-coagulate the blood.Warfarin (Coumadin) is the classic anti-coagulation medication that acts as a Vitamin K antagonist, blocking blood-clotting factors II, VII, IX and X. It is prescribed immediately after diagnosis of a clot or pulmonary embolism, but unfortunately may it take many days for the blood to be appropriately thinned. Therefore, subcutaneous low molecular weight heparin (enoxaparin [Lovenox]), fondaparinux (Arixtra), or regular IV heparin is administered immediately and at the same time as coumadin. It thins the blood via a different mechanism and is used as a bridge therapy until the warfarin has reached its therapeutic level. Enoxaparin injections can be given on an outpatient basis. For those patients who have contraindications to the use of enoxaparin (for example, kidney failure does not allow enoxaparin to be appropriately metabolized), intravenous heparin may be used as the first step in association with warfarin. This requires admission to the hospital.The dosage of warfarin is monitored by blood tests measuring the prothrombin time or INR (international normalized ratio). This is essentially the ratio of the patients clotting ability compared with a normal lab standard. This INR ration allows standardization of testing so that values from different labs can be compared. Therapeutic levels range from 2.0 to 3.0, that is two to three times normal values.Novel oral anticoagulation (NOAC) medications that block factor Xa may be used as another treatment option for pulmonary embolus. These newer medications work almost immediately to thin the blood and do not need the two-step approach of warfarin and heparin together. Medications that have been approved for pulmonary embolus treatment include:

• apixaban (Eliquis)
• edoxaban (Savaysa)
• rivaroxaban (Xarelto)
• dabigatran (Pradaxa)
• betrixaban (Bevxxa)

Basic testing (CBC, electrolytes, BUN, creatinine blood test, chest X-ray, EKG)

Basic testing in the diagnosis of pulmonary embolism may include:

• CBC (complete blood count)
• Electrolytes,
• BUN (blood urea nitrogen),
• Creatinine blood test (to assess kidney function; see below),
• Chest X-ray, and
• Electrocardiogram (EKG or ECG).

CT scan

If there is greater suspicion, then computerized tomography (CT scan) of the chest with angiography can be done. Contrast material (dye) is injected into an intravenous line in the arm while the CT is being taken, and the pulmonary arteries can be visualized. There are some limitations of the test, especially if a pulmonary embolism involves the smaller arteries in the lung. However, similar problems are seen with the more invasive pulmonary angiogram. As CT scan has become more and more sophisticated, not identifying significant emboli is very unusual. It is very important that the contrast material used during the CT angiogram be timed appropriately so that the bolus of dye is not diluted as it travels through the lungs.There are some risks with this test since a patient may be allergic to the contrast material, and the contrast material may damage kidney function, especially if the patient's baseline kidney function (as measured by a creatinine blood test) is abnormal. It may be wise to limit the patient's exposure to radiation, especially in pregnant patients. However, since pulmonary embolus can be fatal, even in pregnancy this test can be performed, preferably after the first trimester.

d-Dimer blood test

If the healthcare professional's suspicion for pulmonary embolism is low, a d-Dimer blood test can be used for reassurance that a blood clot may not be present. The d-Dimer blood test measures one of the breakdown products of a blood clot. If this test is normal, then the likelihood of a pulmonary embolism is very low. Unfortunately, this test is not specific for blood clots in the lung. It can be positive for a variety of reasons including pregnancy, injury, recent surgery, cancer, or infection. D-dimer is not helpful if the potential risk for a blood clot is high.

Echocardiography

Echocardiography or ultrasound of the heart may be helpful if it shows that there is strain on the right side of the heart. If non-invasive tests are negative and the healthcare provider still has significant concerns, then the healthcare professional and the patient need to discuss the benefits and risks of treatment versus invasive testing like angiography.

PERC Rule for Pulmonary Embolus

Being able to assess a patient and determine the risk for pulmonary embolus is very useful, since many patients have chest pain and shortness of breath when seen in an emergency department, urgent care facility, or their health care professional's office or clinic.The PERC rule suggests that in low risk patients, if the answer is no to the following questions, the risk of pulmonary embolus is very low (less than 2%) and no further evaluation for pulmonary embolism is necessary or required:

• Age greater than 50
• Heart rate greater than 100
• Oxygen saturation on room air less than 95%
• Previous history of venous thromboembolism
• Trauma or surgery within the last 4 weeks
• Hemoptysis (coughing up blood)
• Exogenous estrogen prescription
• Unilateral leg swelling (only one leg involved)

Pulmonary angiogram

In the past, the gold standard for the diagnosis of pulmonary embolus was a pulmonary angiogram, where a catheter was threaded into the pulmonary arteries, usually from veins in the leg. Dye was injected and a clot or clots could be identified on imaging studies. This is considered an invasive test and is now rarely performed. Fortunately, there are other, less invasive ways to make the diagnosis. The decision as to which test might best make the diagnosis needs to be individualized to the patient and their presentation and situation.

Pulmonary embolism definition and facts

• Pulmonary embolism (PE) describes the blockage of a pulmonary artery or one of its branches by a blood clot or foreign material.
• Risk factors for the blood clot (thrombus) that travels to the lung (pulmonary embolism) include prolonged immobilization, medications, including birth control pills, smoking, genetic predisposition, an increased number of red blood cells (polycythemia), cancer, pregnancy, surgery, or damage to blood vessel walls.
• Symptoms of pulmonary embolism include:
  • chest pain,
  • shortness of breath,
  • a cough that sometimes produces bloody sputum
  • fast heart rate
  • anxiety
• If not treated promptly, pulmonary embolism may lead to sudden death.
• The diagnosis of pulmonary embolism may be difficult to make, and initially may be missed. Diagnostic strategies need to be individualized to each patient and situation.
• Anticoagulation medication is the treatment for pulmonary embolism, and the patient may be required to continue treatment for a minimum of 3 to 6 months.
• Prevention is the best treatment for pulmonary embolism, which can be accomplished by minimizing the risk factors for deep vein thrombosis (DVT).

Thrombolytic therapy

Pulmonary embolism can be fatal, especially if there is a large amount of clot present within the pulmonary arteries. Tissue plasminogen activator (tPA) is a medication given to break up blood clots, known as thrombolytic therapy. Thrombolytic therapy with tPA is indicated in patients with pulmonary emboli who also have hypotension (low blood pressure), since this may be one sign of shock. Others signs of shock include:

• confusion,
• coma, or
• damage to other organs including the heart and kidneys.

Venous Doppler study

Ultrasound of the legs, also known as venous Doppler studies, may be used to look for blood clots in the legs of a patient suspected of having a pulmonary embolus. If a deep vein thrombosis exists, it can be inferred that chest pain and shortness of breath may be due to a pulmonary embolism. The treatment for deep vein thrombosis and pulmonary embolus is generally the same.

Ventilation-perfusion scans

Ventilation-perfusion scans (VQ scans) use radioactive labeled molecules (often xenon gas, and albumin protein). Gas is inhaled and the low-level radiation is detected throughout the lung fields in the distribution of the pulmonary airways (ventilation). This radioactivity is referred to as gamma radiation and is similar in intensity to sun light rays. The duration of this radioactivity is often measured in hours. Radiolabeled albumin is also injected and the lungs are scanned where these molecules are trapped in the lung following the pulmonary arterial blood path (perfusion). The radiologist then compares multiple different views of perfusion and ventilation looking for areas that are not identical. If blood flow is lacking to a portion of lung often a pie shaped wedge defect is seen, ventilation to this area is usually preserved. This is referred to as a ventilation perfusion mismatch. If a mismatch occurs, meaning that there is lung tissue that has good air entry but no blood flow, it may be indicative of a pulmonary embolus.These tests are read by a radiologist as having a low, moderate, or high probability of having a pulmonary embolism. There are limitations to the test, since there may be a 5%-10% risk that a pulmonary embolism exists even with a low probability V/Q result. Ventilation-perfusion scans (VQ scans) use labeled chemicals to identify inhaled air into the lungs and match it with blood flow in the arteries. If a mismatch occurs, meaning that there is lung tissue that has good air entry but no blood flow, it may be indicative of a pulmonary embolus. These tests are read by a radiologist as having a low, moderate, or high probability of having a pulmonary embolism. There are limitations to the test, since there may be a 5% to 10% risk that a pulmonary embolism exists even with a low probability V/Q result.