No reduction in late ischemic events with rapid troponin protocol for suspected ACS
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Use of a rapid high-sensitivity cardiac troponin T assay protocol for suspected ACS resulted in earlier discharge and less functional testing but was not associated with a reduction in late death or MI at 1 year.
“We know high-sensitivity [troponin assays] have been very useful in the early workup of patients and can rule out acute ACS quite effectively, but the effect on downstream clinical testing is not well defined. We wanted to evaluate the impact of the changes in acute [care] and the outcomes within a patient-level randomized controlled trial evaluating outcomes out to 12 months,” Derek P. Chew, MBBS, MPH, PhD, professor of cardiology at Flinders University in Adelaide, Australia, said during a press conference at the American College of Cardiology Scientific Session.
As previously reported by Healio, 30-day outcomes from the RAPID-TnT study showed that discharge under a 1-hour protocol was safe.
The multicenter, prospective, randomized RAPID-TnT study included 3,378 patients (mean age, 59 years; 53% men) who visited EDs in South Australia with suspected ACS but no evidence of coronary ischemia. The researchers compared care informed by an unmasked 0/1-hour high-sensitivity cardiac troponin T assay (Elecsys, Roche Diagnostics) protocol (reported to < 5 ng/L) with that informed by a masked 0/3-hour protocol (reported to 29 ng/L) with follow-up at 1 year. During the ACC Scientific Session, Chew reported results from 3,270 patients with 1-year follow-up (masked: n = 1,632; unmasked: n = 1,638). Most patients (91.5%) had an initial troponin concentration of 29 ng/L or higher.
Patients who were randomly assigned to the 1-hour unmasked protocol had a greater frequency of discharge directly from the ED (45% vs. 32.3%; P < .001) and earlier discharge (median ED stay: 3.8 hours vs. 4.2 hours; P < .001) compared with the masked 3-hour protocol. Use of the 1-hour unmasked protocol was also associated with less functional testing within 30 days (7.4% vs. 10.9%; P < .001).
During 1-year follow-up, 14.2% of those randomly assigned to the 1-hour unmasked protocol and 12.4% randomly assigned to the 3-hour masked protocol received invasive coronary angiography (P = .13). The researchers reported an increase in invasive coronary angiography in patients with troponin levels of 29 ng/L or lower (1-hour protocol, 11.1%; 3-hour protocol, 8.3%; P = .01).
At 1 year, the rate of all-cause death and MI was not significantly different between the groups: 5% in the 1-hour unmasked protocol group vs. 3.8% in the 3-hour masked protocol group (HR = 1.32; 95% CI, 0.95-1.83; P = .1). In those with initial troponin T concentration of 29 ng/L or lower, the unmasked 1-hour protocol was associated with an increase in death or MI (3.7% vs. 2.3%; HR = 1.6; 95% CI, 1.05-2.46; P = .03).
“Given that there was no overall difference in the study, inference about the less than 29 ng/L group remains exploratory, but it represents 91% of the population and there were no baseline differences,” Chew said during the press conference.
The results were simultaneously published in Circulation.
“Optimal strategies for the management of patients with suspected ACS and low concentration troponin evaluations requires further study,” Chew said.
Reference:
Perspective
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The first important message from this study is that these investigators were able to use registries (electronic health records) and large databases to perform a large study in a pragmatic design. They should be congratulated. We still have a lot to learn about high-sensitivity troponin assays and the algorithms to follow. The unmasked arm actually showed a large number of patients with troponin T less than 29 ng/L. The testing parameters are different when you are unmasked, and surprisingly the rates of death and MI trended higher. In those with a concentration less than 29 ng/L, the rates of death and MI were higher. This begs the question that if unmasking the very low troponin level we actually confuse physicians and make them pursue a cardiac cause, rather to pay attention to other reasons for troponin elevation. This study doesn’t answer this important question. Importantly, the patients enrolled had very low event rates. This should not be missed.
I do not think this study should change our practice, but rather it should help us think about future trials that would address the utility of addressing very low troponin levels in those with suspected ACS and no ischemic changes on ECG. We continue to struggle on these questions as clinicians. We still do not have an answer regarding testing algorithms that are best suited for patients who fit these criteria. We as clinicians do not want to miss any patient who may have an event in the future, and unfortunately this study does not answer this question.
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Chew D, et al. Joint American College of Cardiology/New England Journal of Medicine Late-Breaking Clinical Trials. Presented at: American College of Cardiology Scientific Session; May 15-17, 2021 (virtual meeting).
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