Guideline Guidance: Practical Tips for Finding, Triaging Chest Pain in the ED

A new expert consensus document published by the American College of Cardiology (ACC) aims to provide more practical guidance and detailed definitions regarding the evaluation and treatment of acute chest pain in the emergency department (ED) beyond what last year’s multisociety guidelines set out.

The long-awaited ACC and American Heart Association (AHA) guidelines, which were published in October 2021, endorsed several modalities to search for underlying CAD with a patient-centered approach. Since then, the ACC/AHA have published additional data standards to bring language uniformity to the topic, and last month the Society of Cardiovascular Computed Tomography (SCCT) published guidance on using coronary CT angiography (CCTA) for the evaluation of acute chest pain in the ED.

“Guidelines often cover a fair amount of information, and the goal in the more recent years is to try to make them shorter and more readable,” Michael C. Kontos, MD (Virginia Commonwealth University, Richmond), writing chair of the latest paper, told TCTMD. “As such, oftentimes there may be some gaps in exactly how you can implement the particular recommendations they have in the optimal fashion in clinical practice. That's why our clinical pathway manuscript was developed: to help clinicians try to figure out best practices for management of patients presenting to the emergency department with chest discomfort with possible myocardial ischemia.”

The range of old and new tools available mean that the evaluation of patients “remains challenging,” he said. There’s standard risk stratification based on clinical presentation, there’s the ECG, and then there are high-sensitivity troponin (hs-cTn) assays.

These last, he predicted, are “going to change our current clinical practice, probably for the better, with probably some bumps in the road as people get used to it.”

And implementing these tools, as the current paper makes clear, “is going to have to be a collaborative effort among multiple groups as we outlined—emergency medicine, cardiology, laboratorians, nursing administration—to make them work in the most cost-effective and logistical way,” Kontos added.

hs-cTn Assays and CCTA

In their paper, published online today in the Journal of the American College of Cardiology, Kontos and colleagues offer best practices for the entire clinical timeline of patients presenting to the ED with acute chest pain—from the initial evaluation to use of hs-cTn assays, additional risk stratification and noninvasive imaging, classification and management of myocardial injury, and finally, follow-up and treatment.

“The chest pain guidelines focused both on acute and chronic chest pain, but we chose to focus only on the emergency department acute chest pain process just to try to simplify it,” Kontos explained. “We it made it a little bit shorter, and we also focus primarily on the high-sensitivity assays rather than conventional assays, with the thought that in the next few years everyone's going to be transitioning whether they like it or not.”

Because US uptake of these assays is “well” behind that in Europe, Kontos said that classification of patients as low or intermediate risk is likely going to “change dramatically” in the coming years.

“We actually had this discussion when we were coming up with our recommendations as far as what was the role of imaging this patient population,” he said. “The guidelines put, depending on how you read it, noninvasive imaging at the same level as CTA, or if you look at it the other way, CTA was given one rung up over noninvasive imaging, which obviously created some controversy. I'm not sure exactly how this is going to apply to the high-sensitivity assays.”

While the SCCT paper published last month has value, Kontos said “the majority of studies using CTA in the ED will likely no longer be applicable when high-sensitivity troponin assays are used, as the patients in prior trials who had CTA will now be discharged based on the results of a negative high-sensitivity troponin.

“It'll be interesting to see where this pans out, and CTA may be more valuable for the chronic chest pain population or the stable chest pain population we're seeing as an outpatient,” he continued. “Whereas the in ED group, you'll probably be able to exclude most of those low-risk patients at the initial presentation, just on the basis of their high-sensitivity troponins.”

Issues With hs-cTn Definitions

For Allan S. Jaffe, MD (Mayo Clinic), senior author of a paper published earlier this year calling for more detail and definitions regarding hs-cTn use in the chest pain guidelines, this new document “helps to clarify a lot that was incorrect in the previous document,” he told TCTMD.

That said, he argues that many of the authors of the expert consensus have “very strong biases” regarding certain uses and definitions of hs-cTn assays, “some of which I would argue are not totally correct.”

Inappropriately, in Jaffe’s opinion, this document does not wholeheartedly support the use of a 99th percentile upper reference limit (URL), which is endorsed by the 2021 guidelines. He also claimed the text of this paper might confuse clinicians into thinking the 99th percentile URL should be used for risk stratification—it shouldn’t, he argued, as it’s meant to be a cutoff for diagnosing MI.

Also, Jaffe said, though the authors correctly state that some specificity of the 99th percentile URL is lost when patients have comorbidities like renal failure, they do not clarify that there are additional calculations that can be made to compensate for that.

Other “less than ideal” suggestions made in the current document pertain to definitions of “elevated” and “minimally elevated,” as well as the utility of relative versus absolute changes across serial measurements. For example, he said, Kontos and colleagues propose that absolute, rather than relative, changes at low troponin concentrations provide greater specificity for acute myocardial injury when, in Jaffe’s opinion, the opposite is true.

With that, Jaffe acknowledged that the document “did a lot right” with other definitions that were lacking from the original guidelines. Even if he sees ways in which it could still be refined and improved, he said, “all in all, this is a much, much better document than the prior document, [and] has fewer problems with it.”

Kontos, also speaking the nuances of using hs-cTn in the ED, noted that each high-sensitivity assay has its own quirks and said hospitals should really “know [their] assay,” before integrating one of these tools in their workflow. “Each assay has different cutoff values in different normal ranges, so there really should be a strong collaboration between cardiology, emergency medicine, and the laboratory to come up with a consensus on how they should implement their specific assays,” he advised.

This paper intentionally delved much deeper into how to interpret hs-cTn results to diagnose different MI types—acute or chronic myocardial injury, type 2 MI, and type 1 MI—something Kontos characterized as “somewhat lacking in the guidelines,” a point also echoed by Jaffe.

Kontos acknowledged that “important gaps” remain as to how to best manage these patients. “We attempted to provide the most reasonable recommendations we could come up with, [using] the evidence that we have currently available, but as you know, something new comes out almost every day that may either help us refine what we're doing a little bit better or [lead us] dramatically into a different direction than what we're currently doing,” he said.