 Welcome to approach to pulmonary embolus part 2. In this section, we'll talk about the available diagnostic tests for PE. In part 3, we will talk about how we put it all together. We're hoping to do one of two things with the diagnostic tests. Those that help us rule out other diagnosis, and those that help us rule in PE, or confirmatory tests. First, chest x-ray. What other diagnosis can present that looks like PE? We're shown as a breath and pleuridic chest pain patients could be having an pneumonia, a pleurofusion, pneumothorax, or congestive heart failure. These diagnosis should show abnormal chest x-ray findings. This is a patient with an infiltrate in the right side of the lung. This is likely an pneumonia. Similarly, we want to look for changes that suggestive of CHF, pleurofusion, and pneumothorax on the chest x-ray. Very rarely, we can see some chest x-ray changes in patients with a PE. In this chest x-ray, if you look at the right pleura, you can see a wet shape hyperdensity. This represents an area of pulmonary infarct, also known as hemptons hump. This again is rarely seen. Most patients with PE will have a normal chest x-ray. And therefore, the reason to do the chest x-ray is to rule out other diagnoses, as we discussed before. Next, we'll talk about EKG. The EKG serves two purposes, one to rule out other diseases. What other diagnosis can be helped by doing EKG? It includes ST elevation MI, and pericarditis that can give patients shortness of breath and chest pain. There are also other clues on EKG that point to the patient having a PE. They include the following. Most common seen EKG finding in patients with PE is sinus tachycardia. This is seen in about 40% of patients who have a PE. Sometimes they lead V1 to V4, you can see flip T-waves, like the ones shown here. They can happen in about a third of patients with PE. We sometimes can see a right bundle branch block in patients with PE. This occurs in about 20% of patients. In about 20% of patients with PE, their EKG will show what's known as a S1-Q3-T3 pattern. What does that mean? It means that there is a prominent S-wave in lead 1. A Q-wave in lead 3. And an inverted T-wave in lead 3. Again, it's only seen in 20% of patients with PE. You may also note that this EKG also shows sinus tachycardia and a right bundle branch block. And therefore, we use EKG first to rule out other diagnosis and then we look for other clues that may point towards a PE. Remember that these clues are not present in every patient with PE. And therefore, even if there are no ECG clues, the patient can still have a PE. EKG is not a confirmatory test. What about blood work? How do we use that to help us? We want to do some basic blood work to see what the patient's baseline is. Sometimes in the right context, doing cardiac troponins are helpful. That might rule in other diseases. There's a special test known as a D-dimer in patients for the work of a PE. It is a fibrin degradation product and can go up if there is a PE. We'll talk about how to use it in conjunction with our clinical suspicion in part 3. The next tests are usually used for confirmation of PE. The first one is a VQ scan. It stands for Ventilation Perfusion Scan. It is a test done by Nuclear Medicine. The patient inhales air that has a radionucleotide, the nucleotide that enters the air spaces of the lungs. During the perfusion phase, we inject a radionucleotide intravenously to look for blood flow in the lungs. In patients with PE, there will be a part of the lung that has ventilation. But no blood flow. An example for a VQ scan is here. If we look at this image for ventilation and compare it to the corresponding perfusion image, we can see that there is lack of blood flow in the basal part of the lungs. This is highly suggestive for a PE. A VQ scan is the most helpful in normal lungs. It is not as sensitive or specific as CT scan. A CT scan is the imaging of choice to confirm a PE. It uses a dye to go through the blood vessel. And if there is a clot in the vessel, it is picked up as a filling defect. It can also provide information about pulmonary infarct and give information about other diagnoses as well. This is a still image on a CT scan. You can see that there is IV contrast going through the main pulmonary artery. Where the black arrow is, is a pulmonary embolus. You can see it is less white. That's the filling defect we were talking about before. Sometimes as we said, we can see pulmonary infarct. This is the patient with the hematins hump that we saw on the chest X-ray. It is much easier seen on a CT chest. One last confirmatory test will be in patient with suspicious about a DVT. The Doppler ultrasound will be able to tell us whether there is a deep vein thrombosis or not. Sometimes we will also give alternate diagnosis such as cellulitis or baker's cyst. In summary, we discussed the diagnostic tests we can use in patients that we are working out for a possible PE. We talked about tests that will help us rule out other diagnosis. We talked about blood work, EKG, and confirmatory imaging such as CT, VQ scan and Doppler. In the next section, we will talk about how to put this all together when you are facing a patient who has a possible PE. We hope you find this useful. Thank you for watching.