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So let's talk a little bit about pulmonary embolism.

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So in terms of incidents, 65 per 100,000 in the US.

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Disproportionately more common among the elderly, with a three times higher risk

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for those who are over 70 compared to those who are between 45 and 70.

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Symptoms widely vary.

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So, shortness of breath, pleuritic chest pain, hemoptysis, palpitations,

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light headedness. The Use of Wells criteria Geneva scoring, D-Dimer can be used

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to stratify and determine appropriateness of imaging.

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In my experience,

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that's very variable, and quite frankly, this gets lumped into lots of things of

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could this be PE or could it be something else that is related

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to shortness of breath, pleuritic chest pain, and we see a mixed bag.

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But in terms of PE, specifically, risk factors include

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coagulopathies, trauma, prior surgery, immobility, age, obesity, hormone therapy,

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as well as malignancy. CT, the pulmonary angiogram or the CT with contrast for PE,

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first line tests to assess for pulmonary embolism according to the American College

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of Radiology appropriateness criteria. V/Q scans can be used.

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And these are good tools for patients

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who cannot tolerate contrast or if you're in a global pandemic and contrast is not

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readily available, this is something that can be used

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assuming that you can get the radiotracers.

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In terms of the imaging findings, chest x-ray has got a very low sensitivity,

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although there are a couple of signs that you might look for.

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In my experience, there are many positive

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cases that I have seen with normal chest x-rays,

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so I don't use that as a tool that I rely on heavily.

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For the CTPA, you're looking for the central filling defects.

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Make sure if you're seeing those, look for pulmonary infarcts,

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look for right heartstring, look for evidence of flow disruption.

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So enlargement of the main pulmonary

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arteries, reflux of contrast into the intrahepatic IVC or hepatic veins.

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On the V/Q scan, you're going to look for those mismatch defects.

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So you're going to see decrease

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in perfusion without a decrease in ventilation.

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In terms of some of the pitfalls, particularly for CT, recognize that motion

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artifacts may, in the subsegmental areas, mimic PE as well as mucus plugs.

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So go back and look at your lung windows

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to make sure that what you're seeing is real.

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And one thing to consider if you're

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looking at ALARA principles, is that the V/Q scans can have a significantly lower dose

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of radiation to breast tissue when compared to CT.

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And this is particularly something to consider when you're thinking about

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radio sensitive tissues in patients who are actually pregnant, female patients.

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But keep in mind that oftentimes,

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clinically speaking, what the clinicians are asking for is,

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is this a PE study that you can do to rule out PE,

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but also tell me if there are other things.

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So what my experience has shown me is that 5% to 10% of the time, when they ask

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for PE, there is a PE, but actually 30% of the time, there's some

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other explanation for why the patient may be short of breath or have chest pain.

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So there is value in the chest CT where

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radiographs are not going to tell you everything.

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It's not always going to be PE.

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And so, again, this is a conversation to have locally with your providers

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to understand what the risk stratification of patients is.

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Have they applied the Geneva score,

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the Well's criteria?

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Is this a high risk patient?

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If it's a low risk patient,

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they may consider other things. If they're worried about PE,

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plus a number of other things, it may be actually appropriate to use CT,

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because it's not just for PE, it's for other conditions as well.

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And here are some resources.