Diagnosing a pulmonary embolism
Learn about all the diagnostic tools you'll need to diagnose a pulmonary embolism.
Discover the common lab markers that are monitored in patients with pulmonary embolism. This video, from our Cardiology Lab Essentials course, will help you to shortcut the process and learn about all of the diagnostic tools you'll need to diagnose a pulmonary embolism.
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[00:00:00] In this lesson, I want to explore what diagnostic tools are available to diagnose pulmonary embolism or PE for short. In general, there are three pieces of the puzzle you can use. A pre-test clinical assessment involving your patient's history and physical exam, D-dimer testing, and imaging studies, but let's dig a little deeper. There are a variety of nonspecific symptoms for PE. The most
[00:00:30] frequent symptoms are dyspnea or breathlessness, chest pain, coughing, and symptoms suggestive of deep vein thrombosis like lower leg swelling and pain. Other less common symptoms might include fever, hemoptysis, arrhythmias or syncope. After making a physical exam and taking the patient's medical history, we can integrate all this information using a pre-test clinical assessment. You might wonder why use
[00:01:00] pre-test assessments. As the name suggests, pre-test assessments are performed before lab and imaging studies and can help us to establish how likely it is that our patient actually has a pulmonary embolism. This is known as the pre-test probability. Most diagnostic tests for thromboembolic events are not very specific, so pre-test assessments improve specificity and therefore, also improve the positive predictive value of the lab and / or imaging tests
[00:01:30] chosen thereafter. So, by narrowing down which patient has a high or low probability of having a thromboembolic event, we will gain better diagnostic results and eventually will treat our patient better than without these assessments. The two most commonly used scores are the Wells criteria for pulmonary embolism and the revised Geneva score. Both are based on a combination of vital signs, clinical history, and symptoms. Both have recently been simplified in order to increase our
[00:02:00] clinical practicability. These pre-test clinical tests will classify our patient as having a high, moderate or low probability of having a PE. This information helps us to choose the best diagnostic test to follow. We will talk about these algorithms in another lesson. A rather new pre-test assessment is called the pulmonary embolism rule-out criteria or PERC rule for short. It can be used after performing the Wells score
[00:02:30] if your patient has a low probability of having a PE. If certain inclusion criteria are met, the PERC rule can help you to choose whether further testing is necessary for your patient or not. So, now that we have all the clinical information, we can start performing our diagnostic tests. First, let's talk about D-dimer testing. D-dimers are fibrin degradation products and their plasma levels can be quantified in the lab. D-dimer testing shows a very high negative predictive value.
[00:03:00] Consequently, it is very good at ruling out pulmonary embolism or actually affirm by embolism in general. We were shown that D-dimer testing is very useful in patients with a low or moderate pre-test probability and shown by the Wells score or the revised Geneva score. In patients with the high pre-test probability, D-dimer test results do not provide any helpful additional information, as negative results will not rule out PE in this special situation and
[00:03:30] D-dimer testing should, therefore, not be performed. What about imaging studies? What is the best method to detect a PE? The number one imaging test in PE diagnostics is computed tomographic pulmonary angiography. Other imaging techniques that are suitable for diagnosing PE in certain situations include ventilation / perfusion scintigraphy, compression venous ultrasound, and echocardiography. So, now you can see the
[00:04:00] importance of combining the right puzzle pieces in order to get the right diagnosis. In pulmonary embolism, the use of pre-test clinical assessment test is crucial in order to provide our patient with the best medical care.