BARCELONA, SPAIN — The use of an algorithm with a highly sensitive assay for cardiac troponin T (hs-cTnT) allows physicians treating patients with chest pain in the emergency department to safely and effectively rule out acute MI within one hour.
The hs-cTnT one-hour algorithm ruled out more than 63% of 1282 patients presenting to the emergency department with chest pain and had a negative predictive value of 99.1%, according to the results of the High-Sensitivity Cardiac Troponin T Assay for Rapid Rule Out of Acute Myocardial Infarction (TRAPID-AMI) study presented today here at the European Society of Cardiology 2014 Congress .
Dr Christian Mueller (University Hospital, Basel, Switzerland), the lead investigator, said the goal of the study was "to contribute to an improvement in the early diagnosis of acute myocardial infarction" because an early diagnosis allows for more rapid initiation of evidence-based therapy. Presenting the results during a clinical-trials-update session, he said that delayed "rule in" results in increased morbidity and mortality for acute-MI patients while delayed "rule out" results in increased time in the emergency department, higher costs, and increased patient anxiety.
"This is really a tough population to diagnose," said Mueller of chest-pain patients presenting to the hospital. "Many patients have ECG findings that are difficult to interpret, like complete left bundle branch block."
Reducing Wait Times Down to One Hour
In the emergency department, family history, a 12-lead ECG, and a cardiac troponin (cTn) assay are used to rule in/rule out acute MI cases. For conventional cTn assays, serial sampling over a period of six to 12 hours is required. The ESC clinical guidelines state that if an hs-cTn assay is used, the second measurement can be taken at three hours. TRAPID-AMI sought to determine whether it was possible to further reduce the waiting time to one hour.
For the trial, they used the same one-hour hs-cTnT algorithm as in the APACE study, another trial testing the rule-out/rule-in strategy with hs-cTnT in patients with acute chest pain. In APACE, the researchers were able to accurately rule out or rule in acute MI in 77% of unselected patients with chest pain.
The researchers used an algorithm with a baseline hs-cTnT value <12 ng/L and a one-hour change of <3 ng/L to rule out acute MI. A baseline hs-cTnT value >52 ng/L and a one-hour change >5 ng/L was used to rule in acute MI. All other patients who fell outside these ranges were placed in observation.
Of the 1282 patients, 813 (63.4%) were ruled out using the hs-cTnT algorithm within one hour. For these patients, the negative predictive value was 99.1%. The algorithm ruled in 184 patients and had a positive predictive value of 77.2%. In total, 285 patients were placed in observation, of whom 22.5% had an acute MI identified by further testing. Overall, the strategy ruled out/ruled in more than 75% of patients who presented to the hospital with chest pain.
At 30 days, the mortality rate for patients ruled out using the hs-cTnT algorithm was 0.1%, which was significantly lower than patients in observation and those identified as having an acute MI. This indicates that most patients assigned the rule-out pathway are very good candidates for an outpatient management strategy, said Mueller.
Need to Validate the Algorithm in RCTs
Overall, Mueller said the data showing the effectiveness and safety of the one-hour hs-cTnT algorithm are now "very strong." There is another study, a validation study testing the one-hour algorithm in more than 1000 patients, that shows similar results as TRAPID-AMI. As a result, more than 3500 patients have been studied with the rapid rule-out/rule-in hs-cTnT algorithm.
He added, however, that in the diagnostic arena, investigators often don't have the strong safety signals that would be generated from randomized, controlled clinical trials. He would encourage sponsors, including Roche Diagnostics, the makers of the hs-cTn assay used in TRAPID-AMI, to conduct a prospective randomized trial large enough to acquire mortality data. In the meantime, he is convinced by the data accumulated thus far.
During the clinical-update session, Dr Marco Valgimigli (University Hospital of Ferrara, Italy), who was not affiliated with the study, questioned the effectiveness of the algorithm in patients who presented to emergency department very early, such as those presenting within 30 minutes, or very late, such as those presenting 12 hours or one day, following the onset of symptoms.
For the late presenters, Mueller said the hs-cTnT one-hour algorithm has no different limitations from what is currently used in clinical practice. For example, for patients presenting late following a subacute MI, cTn levels would already have returned to normal, as would hs-cTnT levels. For very early presenters, those appearing within 30 minutes or so, he agrees there are very limited data showing that hs-cTnT can safely rule out acute MI and that physicians should adhere to serial testing for patients who present to the hospital within one hour of symptom onset.
Mueller believes that the introduction of hs-cTn has altered the role of coronary computed tomography (CT). To rule out acute MI in the low-risk patient, there is no justification for the cost and radiation exposure of CT if the same result can be accomplished with high-sensitivity biomarkers. Where CT might aid physicians is with patients in the "observational zone," those with hs-cTnT levels that neither rule out nor rule in acute MI, he said.
Heartwire from Medscape © 2014 Medscape, LLC
Cite this: TRAPID-AMI: High-Sensitivity cTnT Rules Out/Rules In Acute MI in One Hour - Medscape - Aug 30, 2014.