Patients who have myocardial infarction (MI) ruled out in the emergency department but still have intermediate high-sensitivity cardiac troponin concentrations are three times more likely to have coronary artery disease (CAD) than patients who are ruled out with low troponin concentrations, a new study shows.
The finding suggests that high-sensitivity cardiac troponin could help select which patients need coronary computed tomography angiography (CCTA) to find occult CAD and guide the use of preventive therapy to prevent future MI, the authors say.
The study was published September 27 in the Journal of the American College of Cardiology.
“The introduction of early rule-out pathways for myocardial infarction have increased the proportion of patients directly discharged from the Emergency Department,” first author, Kuan Ken Lee, MD, University of Edinburgh Centre for Cardiovascular Sciences, Edinburgh, Scotland, told theheart.org | Medscape Cardiology.
“Current guidelines are unclear how to further evaluate patients without myocardial infarction and there is little evidence to guide further testing in the high-sensitivity cardiac troponin era. As such, most clinicians select patients for further testing and follow up based on whether their symptoms sound like angina or not,” Lee said.
PRECISE-CTCA (Troponin to Risk Stratify Patients with Acute Chest Pain for Computed Tomography Coronary Angiography) was a prospective cohort study that enrolled 250 patients from the emergency department in whom myocardial infarction was excluded.
Patients with intermediate (5 ng/L to the sex-specific 99th percentile threshold) and low (< 5 ng/L) high-sensitivity cardiac troponin concentrations were invited for an early outpatient CT coronary angiogram.
The mean age of the study participants was 61 ± 12 years, and 31% were women.
Overall, 42.4% of patients had angina symptoms, 12.8% had typical angina, and 29.6% had atypical angina. The remainder were classified as having nonanginal chest pain.
Patients with intermediate troponin concentrations were more than three times more likely to have CAD than those with low troponin concentrations (odds ratio, 3.33; 95% confidence interval, 1.92 – 5.78).
In contrast, the proportion of patients with typical or atypical angina who had CAD was the same as those who were considered to have nonanginal chest pain.
Most patients found to have CAD (53.2%, or 83 of 156 patients) did not have a previous diagnosis and were not on antiplatelet and statin therapies before they underwent CCTA.
“We know that patients with intermediate cardiac troponin concentrations are 10-fold more likely to have a cardiovascular event 1 year following the index hospital presentation than those with low cardiac troponins,” senior author Nicholas L. Mills, MD, professor, British Heart Foundation Chair of Cardiology, BHF Centre for Cardiovascular Sciences & Usher Institute, Edinburgh, Scotland, told theheart.org | Medscape Cardiology.
“The routine use of coronary computed tomographic angiography in those with intermediate troponin concentrations could help us identify patients with unrecognized coronary artery disease and target preventative therapy more effectively,” Mills said.
These data can inform the selection of patients for CCTA, but further studies are needed to determine if this approach can improve outcomes, he said.
“We are currently evaluating whether troponin guided CTCA reduces the risk of future myocardial infarction or cardiac death compared to standard care in TARGET-CTCA, a large multicenter, randomized controlled trial funded by the British Heart Foundation.”
Take Troponin Values into Account
“Instead of focusing entirely on the ‘rule-out’ threshold of high-sensitivity troponin, perhaps the time has come to consider the actual troponin values in an individual patient to determine the need for additional testing with CTA [computed tomography angiography],” Kavitha Chinnaiyan, MD, Beaumont Health, Royal Oak, Michigan and James L. Januzzi Jr, MD, Massachusetts General Hospital, Baim Institute for Clinical Research, Boston, Massachusetts, write in an accompanying editorial.
“This study was a very interesting one,” Chinnaiyan told theheart.org | Medscape Cardiology. “Usually what happens is you come into the hospital, you get a high sensitivity troponin, if it is less than the cut off, then you’re sent home; it’s really not a heart attack so we don’t need to worry about it. But that may not be the full story,” she said.
“As these investigators show, even within the normal range, if your troponin is on the higher side, you have a higher burden of disease, your risk factors tend to be higher, and your risk for having an event is probably higher. They highlight the importance of looking at the actual value of the troponin rather than looking at it as being positive or negative,” she added.
The study was funded by the British Heart Foundation. Lee reports that he has received honoraria from Abbott Diagnostics. Mills reports that he has received honoraria from Abbott Diagnostics, Siemens Healthineers, Roche Diagnostics, and Lumira DX. Chinnaiyan reports no relevant financial relationships.