Using highly sensitive troponin I followed by coronary computed tomography angiography (CTA) in chest pain patients improves the accuracy of acute coronary syndrome (ACS) risk stratification, according to results from the ROMCAT II (Rule Out Myocardial Infarction/Ischemia Using Computer Assisted Tomography) trial published in the Journal of the American College of Cardiology: Cardiovascular Imaging.
Low levels of highly sensitive troponin (hsTn) in patients of the emergency department (ED) have been known to rule out myocardial infarction. But increased levels of hsTn are associated with coronary artery disease (CAD) and myocardial perfusion defects, and can also be used outside of the acute care episode to help identify patients at risk for ACS.
“Multiple studies have shown that hsTn assays have increased sensitivity for the detection of ACS and decreased time to assay positivity compared to conventional troponin,” the authors noted. “These assay characteristics suggest a potential for fast and more efficient evaluation of patients presenting to the ED with symptoms suggestive of ACS.”
The ROMICAT II trial included 160 patients suspected of ACS upon arrival to the ED. Patients who had received hsTn were randomly assigned to coronary computed tomography angiography (CTA). Researchers recorded any CAD features including ≥50% stenosis, high-risk plaque features, positive remodeling, and spotty calcium.
The researchers collected blood samples from participants and placed them in tubes containing ethylenediamintetraacetic acid and immediately frozen at -80 degrees centigrade until the end of the study, when it was analyzed for troponin. The limit of detection value was 0.5 pg/L and the 99th percentile value was 49 pg/L.
The patients were categorized into 3 groups: below the limit of detection for the assay, between the limit of detection and the 99th percentile, and above the 99th percentile.
In the total cohort, 10.6% of patients were diagnosed with ACS. In the patients tested with hsTn, 5.6% had a low limit of detection with an ACS rate of 0%, 86.9% were in the intermediate range with an ACS rate of 8.6%, and 7.5% were in the high risk range with an ACS rate of 58.3%.
Patients with <50% stenosis and high risk plaque ruled out ACS in the intermediate hsTn category (ACS rate 0%, while patients with ≥50% stenosis and high risk plaque were at high risk (ACS rate 69.2%). Patients with either factor were considered intermediate risk (ACS rate 7.7%).
The number of patients with hsTn below the limit of detection could be considered for discharge from the ED, and additional research could further increase the discharge rate. Patients above the 99th percentile and those at intermediate risk could also receive more targeted prevention treatments.
“After the first hsTn I and early coronary CTA, about one quarter of patients remain at intermediate risk for ACS, for whom observation could be considered, including serial troponin measurements, aspirin, statin, and a stress test,” the authors noted.
- Ferencik M, Liu T, Mayrhofer T, et al. Highly Sensitive Troponin I Followed by Advanced Coronary Artery Disease Assessment Using Computed Tomography Angiography Improves Acute Coronary Syndrome Risk Stratification Accuracy and Work-up in Acute Chest Pain Patients: Results from ROMICAT II Trial. J Am Coll Cardiol. Oct 14 2015. doi: 10.1016/j.jcmg.2015.06.016.