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High-Sensitivity Cardiac Troponin Testing: Salvo Against Emergency Department Wait Times

June 1, 2020

Protocol combining hs-cTn measurements, modified HEART score enabled earlier discharge of suspected acute coronary syndrome cases without affecting patients' safety.
An approach that combines multiple high-sensitivity cardiac troponin T (hs-cTnT) tests with a modified HEART score shows promise in rapidly ruling out myocardial infarction (MI), sometimes within an hour. Reporting these findings in JAMA Network Open, researchers at University of Texas Southwestern and Parkland Hospital in Dallas suggest that this protocol could reduce wait times and overcrowding in emergency departments (EDs).
Chest pain is a common malady at EDs, accounting for more than 7 million visits each year, according to the Centers for Disease Control and Prevention. U.S. guidelines call for observation and hs-cTn tests over 3 to 6 hours for patients suspected of acute coronary syndrome (ACS). “However, the prevalence of ACS among patients with chest pain is low and decreasing over time,” observed the investigators. Watching low-risk patients with chest pain over long periods contributes to ED overcrowding.
The research team explored a novel protocol: drawing hs-cTnT values at baseline, 1, and 3 hours after ED presentation and employing the modified HEART score (history, electrocardiogram, age, risk factors) to see if this combination would improve resource use in the ED while ensuring patient safety. The retrospective study included data on 31,543 racially and ethnically diverse ED patients who underwent electrocardiographic and hs-cTn testing from Jan. 1, 2017, to Oct. 16, 2018. Researchers implemented the hs-cTnT protocol in December 2017. To assess safety, they looked at ED dwell time, cTn testing to disposition decision times, and final patient disposition to determine resource use outcomes, and readmission rates for MI and death.
ED dwell times declined during the preintervention period (by a mean of 1.09 minutes per month); this decline continued after the intervention by a mean of 4.69 minutes per month. The time from cTn test to disposition was increasing before the intervention by 1.72 minutes per month; after the intervention, it increased at a slower 0.37 minutes per month. And the proportion of patients discharged from the ED increased from 48% before the intervention to 54% afterward. The protocol had no effect on incidence of 30-day major adverse cardiac rates, which remained low throughout the course of the study.
This novel protocol “is safe and improves the efficiency of evaluating patients with possible heart attacks,” said James de Lemos, MD, professor of internal medicine at University of Texas Southwestern and co-author of the study, in a statement. The findings are timely, considering that ED overcrowding has become a pressing concern during the COVID-19 pandemic. “Given the large size of the study and its performance during routine operations in our county hospital, we think the findings would apply to many busy U.S. emergency rooms.”
Experts in the field for the most part were encouraged by the results of the University of Texas Southwestern/Parkland study.
The study’s algorithm validates the fact that you can rule out very early with a hs-cTnT assay, Alan Wu, PhD, director of clinical chemistry and toxicology at University of California San Francisco (UCSF), and Kara Lynch, PhD, associate professor at UCSF’s department of laboratory medicine. “This will be valuable for so many patients,” Wu said.
UCSF looked into implementing a similar protocol in its ED, but that has been put on hold due to the COVID-19 pandemic, Wu added.
Overall, it’s reassuring that there was a modest increase in the number of patients discharged and a reduction in timing of decisions, said Allan Jaffe, MD, a cardiologist and chair of the division of clinical core laboratory services at Mayo Clinic in Rochester, Minnesota. However, some of the study’s methods need a closer look, Jaffe said.
First, the hs-cTnT assay did not rely on the 99th percentile upper reference limit, a key criterion in the Fourth Universal Definition of MI. Second, the researchers used a cutoff value <6 ng/L to rule out MI more than 3 hours after the onset of symptoms, a criteria that “has been endorsed by some and disagreed to by others,” Jaffe said. Also, the HEART score was used to determine downstream testing, “but apparently it was not used to evaluate patients who are presenting. That strategy has not previously been studied and may or may not be adequate,” he added.
The benefit of this approach may vary depending on the population studied, Jaffe continued. “If the population is enriched with lots of low-risk patients, it may work much differently than if there were many more high-risk patients,” he said. “We do know that some patients had events, but we do not know which criteria were used in this group” to rule out MI, whether it was based on a single value taken on admission, or a change at 1 hour or a change of 7 ng/L at 3 hours.
The focus of this study was to exclude MI. The other side of the equation, ruling in MI and myocardial injury, calls for additional evaluations of the criteria, Jaffe said.