March 31, 2014

WASHINGTON, DC — Emergency physicians in Sweden used a high-sensitivity troponin assay to test >14 000 consecutive patients presenting with chest pain and found that virtually everyone with no detectable levels on their first assay—plus an ECG without signs of ischemia—could be safely ruled out for acute MI. Assays like the one used in the study are available in Europe but not the US.

No detectable levels on the high-sensitivity assay for cardiac troponin T (hs-cTnT), defined as <5 ng/L, also independently predicted 100% survival at 30 days, said Dr Nadia Bandstein (Karolinska University Hospital, Stockholm, Sweden) when presenting the observational study here at the American College of Cardiology 2014 Scientific Sessions .

More than two-thirds of patients with the negative test results who were admitted were allowed to go home the same day, half with a discharge diagnosis of unspecified chest pain. "We believe that with this strategy, 20% to 25% of admissions to hospitals for chest pain may be avoided." At her center, she said, that means perhaps "avoiding 600 to 700 hospitalizations every year."

Bandstein is also first author of the study, published in the Journal of the American College of Cardiology and released the same day of her presentation[1].

Dr Prediman K Shah

Speaking with heartwire , Dr Prediman K Shah (Cedars-Sinai Medical Center, Los Angeles, CA), who isn't connected with the analysis, pointed out that it is a retrospective look at data collected at a single center, and therefore one can't make conclusive recommendations on the MI rule-out value of the particular hs-cTnT assay.

On the other hand, he said, "Its size is so large and is [from] a single center, which means they probably have better control on the data than in a multicenter trial. I think that's probably why we're giving it a little more weight" than such a study might generally receive. The flip side, he noted, is that the technique might not work as well when applied to broad practice. "That's why I think this would not be practice-changing quite yet, unless prospectively validated."

As a panelist following Bandstein's presentation, Dr Allan S Jaffe (Mayo Clinic, Rochester, MN), who wasn't involved in the study but has long been a leader in research of biomarkers of myocardial necrosis, was cautiously optimistic about the technique's promise. It's only the latest of a number of studies of hs-cTnT for MI rule-out of chest pain.

"So there are straws in the wind that this strategy will work," said Jaffe. There aren't many, however, in the way of prospective randomized trials. "Still, I think in the long run we will be able to validate the strategy. I just think we need to do it a little bit more rigorously."

Dr Allan Jaffe

Jaffe pointed out pitfalls of the current study that represent challenges for most studies of biomarkers for MI rule-out. It's tempting to view the results as stemming from the assay's sensitivity for necrosis. And that's surely one mechanism. But "more likely than not, there are two mechanisms. The second mechanism is, with very high-sensitivity assays, comorbidities such as heart failure, LV hypertrophy, any structural heart disease, including CAD, will cause the values to rise. So it's very likely that this [also] calls out [that] very low-risk group as part of its mechanism."

The current study looked at 14 636 consecutive patients presenting to the emergency department with chest pain at one of two hospitals in the Karolinska University Hospital system who had at least one hs-cTnT assessment.

Initial assays showed hs-cTnT levels <5 ng/L in 61% of patients, 5 to 14 ng/L in 21%, and >14 g/L in 18%.

HR (95% CI) for 30-Day Outcomes, Negative Predictive Value (NPV) by Initial hs-cTNT Level (ng/L) in Patients Presenting With Chest Pain

End points

<5 ng/L

5–14 ng/L

>14 ng/L

HR (95% CI) NPV (%) HR (95% CI) NPV (%) HR (95% CI) NPV (%)
MI 0.17 (0.09–0.27) 99.8 3.08 (2.48–3.68) 96.9 26.2 (24.5–27.9) 73.8
Death 0.023 (0.001–0.054), 100 0.41 (0.19–0.64) 99.6 2.56 (1.95–3.17) 97.4

Among those with initial levels <5 mg/L, the top discharge diagnoses were nonspecific chest pain in half the group, AF or supraventricular tachycardia in 5.6%, and angina in 5.1%. Interestingly in this group with no detectable hs-cTnT levels, those who were vs were not admitted to the hospital spent similar amounts of time in the emergency department, 203 and 208 minutes, respectively.

Speaking with heartwire , Jaffe pointed out that US physicians have virtually no experience with the high-sensitivity troponin assays; none have been approved here. "Testing this strategy with some of the better US assays is worthwhile. But using this assay or other high-sensitivity assays is not going to happen [here], I would argue, probably for at least another year or so."

Bandstein and coauthors had no disclosures. Jaffe discloses receiving consulting fees or honoraria from Radiometer, Abbott, Ortho Diagnostics, Beckman-Coulter, Trinity, ET Healthcare, Alere, Amgen, Roche, and Critical Diagnostics. Shah discloses receiving research grants from CardioVax.


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