A Way to Funnel Patients From ER Discharge to Further Coronary Testing

With rapid troponin testing in emergency rooms, people who had acute coronary syndrome ruled out could still learn if they had any heart disease that may be confirmed with outpatient testing, the PRECISE-CTCA study showed.

Among 250 people discharged with “normal” high-sensitivity cardiac troponin I (hs-cTnI), those with intermediate hs-cTnI concentrations (between 5 ng/L and the sex-specific 99th percentile) were more likely to have coronary artery disease (CAD) revealed on subsequent coronary CT angiography (71.9% vs 43.4% for peers with hs-cTnI concentrations <5 ng/L; OR 3.33, 95% CI 1.92-5.78), reported Nicholas Mills, MD, of the University of Edinburgh in Scotland, and colleagues.

The strategy of troponin-guided coronary CT angiography after exclusion of myocardial infarction (MI) found 62.4% of study participants with reference-level troponin to have CAD. Over 53% of these individuals did not have such a diagnosis beforehand, and more than 63% were not on antiplatelets or statins before imaging, the team said in the study online in the Journal of the American College of Cardiology.

“Our finding that many of these patients had … unrecognized underlying CAD and were not on preventative medical therapy before undergoing CCTA [coronary CT angiography] suggested that targeting this at-risk group could present an opportunity to improve outcomes,” the researchers wrote. “At present, hs-cTn is primarily applied to rule in and rule out acute myocardial infarction using fixed thresholds. However, it is now increasingly recognized that cardiac troponin concentrations within the normal reference range are a continuous marker of risk and can be used to improve risk stratification further.”

Writing in an accompanying editorial, Kavitha Chinnaiyan, MD, of Beaumont Health in Royal Oak, Michigan, and James Januzzi, Jr., MD, of Massachusetts General Hospital and Baim Institute for Clinical Research in Boston, said: “One might leverage the information from an hs-cTn in the normal range for further decision making beyond simple discharge. This is where the intersection of markers and imaging might be robust.”

Chinnaiyan and Januzzi called it “tempting” to consider the troponin-guided imaging strategy from PRECISE-CTCA to be “an important new paradigm of care,” but cautioned that the study did not report clinical outcomes.

The ongoing TARGET-CTCA trial will probe outcomes after a similar testing strategy in over 2,200 people.

“Although we await more data on the impact of these findings on hard events, we can assume that a greater burden of CAD portends worse outcomes as previously demonstrated, and better recognition and treatment of higher-risk patients would be expected to afford greater ability to treat with greater precision,” the editorialists surmised.

PRECISE-CTCA was a prospective cohort study conducted in 2018-2020 at Royal Infirmary of Edinburgh. Participants had had MI ruled out, given their hs-cTnI concentrations below the sex-specific 99th percentile, before they were discharged and referred to coronary CT angiography as soon as possible. Results were provided to the patient and their clinicians with recommendations to start secondary prevention if CAD was identified.

This cohort comprised 250 people; average age was 61.4, and 31% were women.

“Several important and interesting findings were noted in this study,” the editorialists continued. “Patients in the normal but intermediate hs-cTnI group had higher TIMI (Thrombolysis In Myocardial Infarction) and GRACE (Global Registry of Acute Coronary Events) risk scores at index presentation, higher atherosclerotic burden, and higher probability of more severe CAD.”

The difference in CAD prevalence between intermediate- and lower-troponin groups persisted whether patients did or did not have symptoms of angina, Mills and co-authors reported.

The intermediate-troponin group did not have significantly higher odds of finding obstructive CAD (29.9% vs 19.3% for peers with lower troponin, OR 1.79, 95% CI 0.95-3.39). However, the prevalence of obstructive CAD was “lower than anticipated, and this reduced the power of our analysis,” the researchers said.

“We evaluated the severity of CAD based on the degree and extent of coronary artery stenosis rather than performing more detailed analysis of plaque phenotype to identify high-risk plaque features or an evaluation of coronary physiology using CT fractional flow reserve,” the team added.

Moreover, the observational study left room for selection bias, the researchers noted.

Nevertheless, Chinnaiyan and Januzzi said that for people with acute chest pain, “troponin assays could function as gatekeepers to anatomic testing, and considering the combined strengths of [hs-cTnI] and [CT angiography], it would make clinical sense to use them together for risk stratification and prognostication that is actionable.”