BackTable Article

Pulmonary Embolism Diagnosis and Imaging

Quynh-Anh Dang • Aug 23, 2021

Pulmonary embolism (PE) can be fatal if it is not detected and treated promptly. In this article, interventional cardiologist Dr. Eric Secemsky and Dr. Sabeen Dhand discuss considerations for diagnosing pulmonary embolism, risk stratification guidelines, and imaging methods. This is the first installation of a three-part article series on pulmonary embolism diagnosis and interventions from the BackTable Podcast.

We’ve provided the highlight reel in this article, but you can listen to the full podcast below.

The BackTable Brief

• American Heart Association (AHA) and European Society of Cardiology (ESC) criteria are commonly used for risk stratification of pulmonary embolism. The ESC criteria provides a PESI score, which further specifies differences in severity between cases that fall within the intermediate risk category.

• In pulmonary embolism workup, the major cardiac enzymes measured are B-type natriuretic peptide (BNP) and troponin. Dr. Secemsky has observed that elevated troponin could likely signal acute pulmonary embolism, while elevated BNP could likely signal subacute pulmonary embolism.

• Diagnosing pulmonary embolism is possible through imaging with echocardiogram and/or CT. Both are sources of valuable information: while CT can provide the RV/LV ratio, echocardiogram can provide the right ventricle systolic pressure (RVSP).

Table of Contents

Pulmonary Embolism Diagnosis and Classification

Imaging for Pulmonary Embolism: CT and Echocardiogram

Pulmonary embolism diagnosis involves risk stratification, cardiac enzyme studies, and echocardiogram and/or CT

Pulmonary Embolism Diagnosis and Classification

In pulmonary embolism diagnosis, it is important to conduct risk stratification in order to guide treatment selection. The two main risk stratification schemes for pulmonary embolisms are the (American Heart Association (AHA) criteria and the European Society of Cardiology (ESC) criteria which yields a PESI score (or simplified PESI score). The AHA criteria outlines three groups: massive, submissive, and low risk. Similarly, the PESI score also outlines three groups: high risk, intermediate risk, and low risk. Additionally, it further divides cases into the subclassifications of “intermediate high risk” and “intermediate low risk” according to whether there are RV dysfunction and biomarkers, or RV dilation and biomarkers. Beyond these formal classifications, it is important to evaluate the overall clinical picture to determine how to escalate therapy.

[Dr. Sabeen Dhand]
How does your practice classify patients with PE?

[Dr. Eric Secemsky]
One thing that we still are getting our heads around is how to classify PE. I think we've kind of got a good criteria in terms of classifying massive, submassive, and non-submassive (some people call it low risk)... But we are trying to understand, particularly within that submassive pulmonary embolism group, what is high risk?

In the AHA criteria right now, it is poorly defined. It says that “submassive” means you have any evidence of RV dysfunction on CT scan or echo, or any signs of RV necrosis with biomarkers of BMP, or cardiac enzyme troponin is elevated.

On the other hand, the European guidelines go a little step further. They first say, “Let's look at your PESI score or your simplified PESI score.” So, let's put your clinical context at the front of that decision. From there, if you have both a high PESI score with RV dysfunction and biomarkers, you fall into the intermediate high risk group. Or, if you have [a high PESI score and] either [RV] dilation or biomarkers that are positive, then you are in the intermediate low risk group.

The PESI score is a little bit more refined in terms of how it classifies these patients. Empirically, when our PE phone calls, we are looking to see if they have any type of vital sign abnormalities. You know, it's a little bit more subjective. We’re asking: What's their heart rate? How much oxygen are they on? Can they complete full sentences? How stable is their blood pressure? Then, we're really looking for evidence of RV dysfunction. If it's overnight, we get a CT scan. If it's daytime, we'll get an echocardiogram. Then, we ask: Are both biomarkers [troponin and BNP] elevated? And we'll get lactate also. We could talk about some refinements, but those are the heart of the patients that we're managing in the hospital.

There's also the massive classification, which is the smaller nugget of the PE patients, but that's where the clinical side is.

[Dr. Sabeen Dhand]
That's good. I'm glad you kind of got into the questions that you ask because there can be a lot of information overload with the European guidelines and the PESI score, and the distinction between intermediate high risk and intermediate low risk. It’s important to look at the real clinical picture. Can the patient finish a sentence? How much are they struggling? That’s a huge source of information. The clinical picture is what really wins in this.

[Dr. Eric Secemsky]
Yeah. The best part of this was, when we first started, we got those PE calls and everything was about how much clot there was. Saddle pulmonary embolism, clot in all the lungs. Then you'd say, "Okay, well how is the patient?" And they're like, "Oh, they're on room air, heart rate is in the 70s, blood pressure's normal." We'd say, “Wow, it's pretty amazing that they're tolerating all this clot burden,” but, on the other hand, it's hard to push yourself to get excited about intervention with some risk, maybe not a ton of risk, but some risk in a patient like that.

Now, our phone calls are really brief about the clot burden, really brief about if it is more about binaries or RV dysfunction or not. Then, it's about the patient interview and how the patient is doing. You know that with a patient who can't finish a sentence or is on a non-rebreather, you're going to have to escalate therapy. On the other hand, there's the stable patient who didn't even know they had a PE, and it is easier to make that decision.

[Dr. Sabeen Dhand]
Clot burden is not the key, but it is all the physiologic effects of what that [clot burden] causes.
The cardiac enzymes used are basically BNP and troponins? Anything else?

[Dr. Eric Secemsky]
The main ones are BNP and troponin. We are starting to get into the weeds of the PERT Consortium Database, looking at how people manage PE across the nation, and it's infrequent that centers order both of those. BNP is a little bit more common than troponin. Troponin often falls a little bit more on the cardiac coronary side, and so it's not always ordered. But we look at both of those.

What I have observed is that when the BNP is elevated but the troponin is not, you have to start thinking more about a subacute PE. Now, again, this is empiric, I don't want anybody to think this is fact. Normally, when I see the troponin elevated, usually it's a more acute PE, a little bit more severe early onset RV dysfunction. When they're both elevated, you know they are a particularly higher risk acute PE patient.

Outside of that, we've been making a push to get lactates as well, and I think that's really helpful to start triaging and risk stratifying the right patient for a more aggressive upfront approach. When the lactate is elevated, we know then any hypoperfusion to these organs is a sign that we might need to really do something to relieve the pressure on the RV. We've been looking to get lactates in addition to the troponin and BNP. Those are the big three. The nice part is that the ER is so used to ordering those.

Imaging for Pulmonary Embolism: CT and Echocardiogram

Dr. Secemsky speaks about dual use of CT and echocardiogram in diagnosing pulmonary embolism. He highlights some drawbacks and benefits of using echocardiograms to evaluate right heart dysfunction. Dr. Secemsky believes that the quality of echocardiograms are more technician-dependent and more affected by male/female patient physique than that of CT scans. The CT scan is also used for measuring RV/LV ratio. However, he prefers to use echocardiograms to determine right heart systolic pressure and pulmonary hypertension in follow-up care.

[Dr. Sabeen Dhand]
In using echocardiogram versus CT to evaluate for RV dysfunction, how often do you find a discrepancy of echocardiogram being more accurate than CT?

[Dr. Eric Secemsky]
We usually get both. We are a little bit spoiled because our cardiology fellows are there 24/7 and they carry around these small scanners to look at the function of the heart, or they'll bring the big machine down. So, we usually get both, but it is a limited view.

Recently, we did a paper that was in Vascular Medicine, looking at presentation and treatment differences between men and women with PE. We found that women more often tended to have a little bit more CT abnormalities for RV function than for echocardiograms. This was a large data set, so I don't have the granularity to tell you if the study was of the highest quality for the echocardiogram. Echocardiograms are a bit technician-dependent. It's not always the easiest to open up the RV. You often will get a short view of it and it will make it look worse than it is. It’s easy to tell when it looks really bad. Obviously, the habitus part for women might have driven that a little bit.

[Dr. Sabeen Dhand]
Yes, ultrasound is always operator-dependent, so you always have to keep in mind that variable with any ultrasound.

[Dr. Eric Secemsky]
Once I see it on a CT scan and it [RV/LV ratio] is really over the ratio of one to the LV, I feel pretty confident that I know there is dysfunction. The echocardiogram can give you more specific data, but I can't say that I act on anything more. We will report things like TAPSE, but probably the most helpful thing is to have an echocardiogram once they are nearing discharge to know what to surveil for when you're in follow-up. It is so much easier to get an echo for someone and look at RVSP and pulmonary hypertension than sending them back to a scanner just to get an RV/LV ratio. You wouldn't want to do that very often. So, I like the echo for follow-up.

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Podcast Contributors

Dr. Eric Secemsky

Dr. Eric A. Secemsky, MD, MSc, RPVI, FACC, FSCAI, FSVM is the Director of Vascular Intervention and an Interventional Cardiologist within the CardioVascular Institute at Beth Israel Deaconess Medical Center (BIDMC).

Dr. Sabeen Dhand

Host Dr. Sabeen Dhand is a practicing interventional radiologist with PIH Health in Los Angeles.

Cite This Podcast

BackTable, LLC (Producer). (2021, April 12). Ep. 120 – Pulmonary Embolization Interventions & Response Teams [Audio podcast]. Retrieved from https://www.backtable.com/podcasts

Medical Disclaimer

The Materials available on BackTable.com are for informational and educational purposes only and are not a substitute for the professional judgment of a healthcare professional in diagnosing and treating patients. The opinions expressed by participants of the BackTable Podcast belong solely to the participants, and do not necessarily reflect the views of BackTable.