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High-sensitivity cardiac troponin T predicted patients with chest pain at minimal risk
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WASHINGTON — Patients presenting to the ED with an undetectable level of high-sensitivity cardiac troponin T and whose electrocardiogram shows no sign of ischemia have a minimal risk for MI or death within 30 days and can be safely discharged, according to research presented here.
In a study of 14,636 patients (mean age, 47 years; 53% women) who reported to a Swedish ED with chest pain from 2010 to 2012, researchers examined patients’ blood levels of high-sensitivity cardiac troponin T. The goal of the study was to evaluate if an undetectable high-sensitivity cardiac troponin T level (<5 ng/L) and an ECG without signs of ischemia can rule out MI in the ED, researcher Martin Holzmann, MD, PhD, said in a press conference at the American College of Cardiology Scientific Sessions.
Martin Holzmann
Of the patients studied, 61% had an initial high-sensitivity cardiac troponin T <5 ng/L, 21% had 5 to 14 ng/L and 18% had >14 ng/L.
MI incidence very low
The primary outcome was fatal or nonfatal MI within 30 days. During follow-up, 0.44% of the 8,907 patients with an undetectable high-sensitivity cardiac troponin T were diagnosed with MI, of whom 0.17% showed no signs of ischemia on ECG. According to the researchers, this means that only one in 594 patients who seek medical attention for chest pain, but have no signs of heart damage on an ECG and undetectable levels of high-sensitivity cardiac troponin, are actually at immediate risk for MI.
The negative predictive value in patients with undetectable high-sensitivity cardiac troponin T was 99.8% for MI and 100% for death within 30 days, Holzmann said. This relationship held true regardless of the patients’ risk factors for MI or how long they had experienced symptoms, he said.
In patients with undetectable high-sensitivity cardiac troponin T, there were 2 deaths within 30 days. At 1 year follow-up, there were 38 deaths, of which 32 were caused by cancer and two by CV, Holzmann said.
Simple strategy
“We believe that up to 20% to 25% of all admissions to the hospital because of chest pain may be prevented using our simple strategy,” Holzmann said.
Clinical implications include avoidance of unnecessary admissions, potential reduction of overcrowding of the ED and saving time for the patient and doctor, he said.
The results were published simultaneously in the Journal of the American College of Cardiology by Nadia Bandstein, MD, Holzmann and two other colleagues, all from the department of emergency medicine at Karolinska University Hospital and Karolinska Institute, Sweden.
Nadia Bandstein
According to the researchers, this is the first large study to specifically examine the use of high-sensitivity cardiac troponin T to predict MI risk.
Current guidelines recommend that high-sensitivity cardiac troponin T be analyzed at least 3 hours after the onset of chest pain. Holzmann said these findings suggest that only one measure of the biomarker needs to be taken, and may allow some patients to be discharged directly from the ED. – by Katie Kalvaitis and Erik Swain
For more information:
Bandstein N. Late-Breaking Clinical Trials III. Presented at: American College of Cardiology Scientific Sessions; March 29-31, 2014; Washington, D.C.
Bandstein N. J Am Coll Cardiol. 2014;doi:10.1016/j.jacc.2014.03.017.
Disclosure: Bandstein and Holzmann report no relevant financial disclosures.
Perspective
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Allan S. Jaffe, MD
The recent retrospective late-breaking clinical trial from Sweden using high-sensitivity cardiac troponin values to exclude acute MI in the initial samples from patients in the emergency room builds on a very substantial literature substrate. Over time, a variety of research has suggested that undetectable or very low levels of high-sensitivity cardiac troponin levels in initial samples can be used for this purpose. Higher-sensitivity assays may detect the release of cardiac troponin earlier, but it is likely that much of the negative predictive value of this technique relies on the fact the comorbidities (diabetes, hypertension, renal disease, HF and structural heart disease) that lead to CAD and acute MI raise cardiac troponin levels such that individuals with such risk factors may have normal values but rarely will have extremely low values. Combining an undetectable high-sensitivity cardiac troponin T value with a normal ECG likely does provide robust negative predictive value for AMI; in this study, it was claimed to be 99%. However, because of the above mechanisms, this is likely an approach that will only work in low-risk patients.
In addition, the present study has several problematic areas. The cohort does not contain, as far as one can tell, many patients who presented early after the onset of symptoms. In addition, the criteria used to exclude acute MI are not included so that there is no assurance that the individuals evaluated were appropriately diagnosed. Indeed, the records of those in whom it is claimed acute MI was excluded were not reviewed, and the authors acknowledged after the presentation that aside from the 21% of patients who were admitted, probably very few had multiple samples. Thus, at the very least, the rule-out diagnosis was not quality assured and the possibility of misdiagnoses is high. Accordingly, although enthusiastic about the concept, this researcher suggests caution about this particular report.
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