RAPID-TnT Supports 0/1-Hour Troponin T protocol, but With a Wrinkle

Patrice Wendling

September 06, 2019

PARIS — Patients presenting with suspected acute coronary syndrome have similarly low rates of death or myocardial infarction (MI) within 30 days when triaged with a 0/1-hour high-sensitivity cardiac troponin T (hs-cTnT) protocol or standard testing, according to results of the RAPID-TnT study.

The 0/1-hour protocol allowed more patients to be discharged from the emergency department (ED) than the standard 0/3-hour protocol (45.1% vs 32.3%; P < .001) and without an increase in functional cardiac testing.

The more rapid protocol, however, led to more revascularizations within 30 days (2.2% vs 0.9%; P = .002) and an increase in myocardial injury or infarction (1.6% vs 1%; P = .004) in the subgroup with a low initial troponin level of 29 ng/L or less.

"That small increased signal of increased MI is something we are going to need to watch carefully," lead investigator Derek Chew, MD, Flinders Medical Centre, Adelaide, Australia, told theheart.org | Medscape Cardiology. "Going forward, we are going to need to put study into evaluating what to do about those patients more carefully, rather than throwing revascularization at them."

"The key question is essentially whether that revascularization is appropriate and actually prevents further events or whether it is inappropriate and doesn't prevent future events. We will know that by 12 months," he said.

The Rapid Assessment of Possible ACS in the Emergency Department With High-Sensitivity Troponin T (RAPID-TnT) study randomly assigned 3378 patients at four South Australian hospitals to a 0/1-hour protocol using hs-cTnT (Elecsys, Roche Diagnostics) or a standard 0/3-hour protocol with troponin results masked below 29 ng/L. Randomization was performed after senior ED physician interpretation of initial ECG results.

Because of concerns regarding a higher rate of abnormal troponin results and increased invasive testing, researchers decided to align the reported lower limit of the fifth-generation assay (14 ng/L) to the fourth-generation assay level of ≤ 29 ng/L, Chew explained. Because local EDs remained masked to troponin levels below 29 ng/L for all patients receiving emergency care prior to the trial, it provided an ideal opportunity to evaluate the impact of test reporting on subsequent care among physicians with no previous experience with hs-cTnT results below 29 ng/L.

In the standard-protocol group, 33.4% of patients were admitted based on a troponin T level ≥ 29 ng/L and a history of prior coronary artery disease, and 66.5% were discharged from the ED. In the 0/1-hour protocol group, MI was ruled out in 72.1% of patients.

The primary endpoint of death or MI within 30 days occurred in 1.0% of patients randomized to each group (P = .006 for noninferiority).

Among patients discharged from the ED, the 0/1-hour protocol had a negative predictive value of 99.6% for 30-day death or MI. Median ED length of stay was also reduced from 5.6 hours to 4.6 hours with the 0/1-hour protocol.

Just days earlier in another hotline session, results of the HiSTORIC trial showed that a single early rule-out troponin I protocol increased the proportion of patients discharged from the ED by 57% without an increase in 1-year event rates.

"HiSTORIC focused on those patients who were able to be ruled out and so this all sits very comfortably," Chew said when interviewed. "Surprisingly, our event rate for those who are ruled out is exactly the same. So I think that the data for both troponin I and troponin T are very, very consistent and highly reassuring."

"Europe has had much greater uptake of high-sensitivity troponins than North America," he said. "I think in what we can comfortably see, if we receive a rule-out recommendation, we can be assured that the patient is safe."

Asked whether the finding of myocardial injuries in the subgroup with low initial troponin might put some clinicians off the 0/1-hour hs-cTnT strategy, Chew replied, "I think that it is unlikely to chill the enthusiasm because the problem of emergency route congestion is a big one. So being able to be able to allow people home earlier and faster and safely is a significant gain."

Commenting on RAPID-TnT for theheart.org | Medscape Cardiology, Kurt Huber, MD, Sigmund Freud University Medical School, Vienna, Austria, said, "It's an important trial, first, because a 0/1-hour strategy has been so far only proven with a so-called ultra-sensitive troponin T assay. I assume the assay used here is the usual high-sensitivity assay and you usually have a 0/3-hour strategy."

"What he said is that patients who after 1 hour already had a slight increase in troponin, these patients in a higher number went to diagnostic cath," Huber said. "What he did not tell us is how frequently these patients had no coronary disease. So this would be quite interesting."

More concrete data are also needed on the subgroup of patients who went on to experience myocardial injury, including potential background reasons like hypertension or heart failure, Huber said.

Invited discussant Christian Eugen Mueller, MD, University Hospital Basel, Switzerland, said RAPID-TnT was a "major achievement" and represents a "very, very important pillar" to the data documenting the safety and efficacy of the ESC 0/1-hour algorithm."

"This important dataset confirms the decision that many of you have already implemented in your site," he said.

The study was funded by the National Health and Medical Research Council of Australia, with additional support through a restricted educational grant from Roche Diagnostics. Chew has reported no relevant financial relationships. Mueller has reported receiving research support/consulting fees paid to his institution from several diagnostic and pharmaceutical companies.

European Society of Cardiology (ESC) Congress 2019. Presentation 6041. Presented September 3, 2019.

Circulation. Published online September 3, 2019. Full text

Follow Patrice Wendling on Twitter: @pwendl. For more from theheart.org | Medscape Cardiology, follow us on Twitter and Facebook.


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.