ACC Chest Pain Pathway Performs Well Overall, Less So for Those With CAD

The American College of Cardiology (ACC) expert decision pathway for chest pain can safely and effectively rule out acute coronary syndromes in most patients, but not for those with known coronary artery disease, according to a US validation study.

“The message really is that you can't just say that you have a nonischemic EKG and two normal high sensitivity troponins in a patient with prior coronary disease and that they are going to do well for the next 30 days,” lead author Simon A. Mahler, MD (Wake Forest University School of Medicine, Winston-Salem, NC), told TCTMD. “Many of these patients probably still need the more traditional evaluation.”

The pathway, as covered by TCTMD, was published in 2022 as a companion document to the 2021 ACC and American Heart Association (AHA) chest pain guidelines. It was developed to be practical guide for clinicians who evaluate and treat acute chest pain in the emergency department (ED), including a heavy focus on high-sensitivity troponin (hs-cTn) assays.

Because much of the data that the ACC pathway was based on was from Europe, Mahler explained that “we felt like it was important to try to validate their recommendations within a US ED patient population.”

Commenting to TCTMD on the new analysis, Matthew Tomey, MD (Icahn School of Medicine at Mount Sinai, New York, NY), said the validation affirmed his expectations. “As has been appreciated to date, mostly outside the United States, by definition high sensitivity and undetectable values of high-sensitivity troponin are pretty good ways of ruling out an acute coronary event,” he said. “What this study did a nice job of demonstrating is that pretest likelihood of disease is still relevant as we think about the implications of a given test result for the diagnosis.”

It “makes sense” that those with prior CAD would have a higher event rate given their higher pretest likelihood of disease, he continued. Because of that, and because the ACC pathway isn’t “exclusively predicated on using high-sensitivity troponins, . . . I don't know so much that these results serve to require a change to the pathway so much as they underscore the need to integrate the pathway and broader use of clinical judgment in the evaluation of any patient presenting urgently with a chest pain syndrome.”

Worse Performance With Known CAD

For the validation study, published in the April 2, 2024, issue of the Journal of the American College of Cardiology, Mahler and colleagues completed ACC pathway assessments—ECGs and 0- and 2-hour hs-cTn assays—on 14,395 patients (median age 56 years; 51.7% women) treated at one of five US EDs between November 2020 and July 2022. Slightly under one-quarter (23.5%) had known CAD.

The primary safety outcome of all-cause death or MI at 30 days was reported in 8.1% of the population. Overall efficacy—defined as the proportion stratified to the rule-out zone—of the ACC pathway was 48.1% (95% CI 47.3%-49.0%). Among the 6,930 patients in the rule-out zone, only 22 (0.3%) had death or MI and 43 (0.6%) had MACE at 30 days, leading to negative predictive values (NPVs) of 99.7% (95% CI 99.5%-99.8%) and 99.4% (95% CI 99.2%-99.6%), respectively.

When the analysis was limited to patients with known CAD, 20% were identified in the rule-out zone but 1.5% had death or MI within 30 days. Here, the negative predictive value was 98.5% (95% CI 97.3-99.3%), which was driven largely by missed MIs (1.2%). In this group, the rate of 30-day MACE was 4.0%, including 2.5% coronary revascularizations without MI (NPV 96.0%; 95% CI 94.2%-97.4%).

On multivariable adjustment, known CAD was significantly associated with death or MI at 30 days regardless of ACC pathway classification, with the strongest relationship seen among those who fell in the rule-out zone (OR 4.9; 95% CI 2.1-11.5).

“We were pleased to see that the overall framework performed quite well,” Mahler said. “But that we may want to tweak it a little bit in future iterations to include known coronary disease as part of the branching logic and give a little bit of extra caution when we are caring for patients with known coronary disease.”

Added Layer of Caution

In an accompanying editorial, Michael C. Kontos, MD (Virginia Commonwealth University, Richmond), and James A. de Lemos, MD (University of Texas Southwestern Medical Center, Dallas), who co-authored the 2022 ACC pathway paper, argue that the study did not validate the entire pathway, but only part of it.

“It is important to recognize that the ACC Consensus Pathway outlined a comprehensive evaluation process that includes initial patient assessment, electrocardiogram interpretation, and hs-cTn measurement as part of a validated clinical pathway which also includes triage, management, disposition, and follow-up guidance,” they write. “As such, the study by Mahler et al is not a true ‘validation study’ of the ACC Consensus Pathway, but an assessment of one component of what is designed to be a comprehensive assessment.”

Acknowledging that chest pain protocols should continue to evolve with new evidence, Kontos and de Lemos write that the study highlights something new about how high-sensitivity cardiac troponin should be used to evaluate these patients in the ED. Specifically that “relying on hs-cTn values alone without clinical assessment may lead to discharge of some patients at higher than desired risk,” the editorialists conclude. “Their findings reinforce the recommendations from the ACC Consensus Pathway that reliance on hs-cTn alone is not recommended, and that clinical assessment and judgment should always be used to inform discharge decisions.”

Tomey agreed. “Clinical judgment is still an important part of [evaluation],” he said. “In patients with known coronary artery disease, we need to have an added layer of caution.”

Further, he pointed to the fact that the negative likelihood ratios were each “very good,” at -0.05, with regard to 30-day death or MI regardless of whether the patients had known or no known CAD. “It's just that in a context of a higher prevalence of disease by definition, in the case of those with known coronary disease, the likelihood of events after the test results is inherently going to be higher,” he said. “What's nice about that is that that's really a pure assessment of the performance of the test as opposed to being confounded by the pretest likelihood.”