Positive Cardiac Troponin in Stroke Signals Mortality Risk

April 12, 2017

Elevated cardiac troponin levels in patients with acute ischemic stroke were independently associated with an increased risk for long-term mortality in a new study.

The study, published online in Stroke on April 5, was conducted by a team led by Peter Wrigley, MD, from the University of Cincinnati, Ohio.

"We found that stroke patients with a positive troponin test had much higher mortality at 30 days, 1 year, and 3 years," Dr Wrigley told Medscape Medical News. A raised troponin level was a stronger marker of risk than either age or size of stroke in the study.

"Our population had relatively small strokes (median stroke score of 3) and an average age of 69," Dr Wrigley noted. "They should be quite low risk, but 60% of those with raised troponin levels had died by 3 years. This is pretty startling. A limitation of the study is that we don't know what patients died from, but I would suspect we are picking up cardiac deaths here."

"Their findings show how closely the brain and heart are linked," he added. "In practice at present, we normally monitor troponins in stroke patients, but we don't really know what to do when we see a positive result. We talk to the cardiologists, but they generally suggest that if patients are not actually having [a myocardial infarction], the raised troponins are probably just markers of acute stress caused by the stroke, but our results are not in line with this."

Proxy Cardiac Stress Test

"Our study suggests that stroke could be thought of a proxy cardiac stress test — a warning of underlying atherosclerosis — and an increased troponin is a further sign of cardiac risk in this group. I would suggest that acute ischemic stroke patients with raised troponins should undergo a full cardiology work-up," Dr Wrigley said.

However, their results probably need to be confirmed in a prospective study to determine whether further cardiac evaluation in this group might prevent the higher long-term mortality rates they observed, he cautioned. "We hope our results will lead to discussion between stroke doctors and cardiologists and stimulate more research in this area."

The current study was part of a larger epidemiological study involving all patients admitted with an ischemic stroke in the Cincinnati area. The researchers screened emergency department admissions from 2010, using International Classification of Diseases discharge codes, and identified all physician-confirmed acute ischemic stroke cases by retrospective chart review. Positive troponin was defined as elevation in cardiac troponin above the standard 99th percentile. Multiple logistic regression was performed, controlling for stroke severity, history of cardiac disease, and all other stroke risk factors.

Results showed that of 1999 acute ischemic stroke cases, 1706 (85.3%) had a cardiac troponin drawn and 1590 (79.5%) had echocardiograms.

Positive troponin occurred in 353 (20.7%) of 1,706 patients, and 160 (10.1%) of 1,590 had echocardiogram findings "of interest." Among 1,377 who had both tests performed, raised troponins were independently associated with echocardiogram findings (odds ratio, 2.9; 95% confidence interval [CI], 2.0 - 4.2).

For those 1,377 patients who had both tests and had positive troponins, mortality was 26% at 30 days, 47% at 1 year, and 60% at 3 years. Raised troponins were independently associated with death at all points.

This association was similar when concurrent acute myocardial infarctions, diagnosed by the treating physician in 49/1377 (3.5%) cases, were removed from the analysis, with raised troponins being associated with a three times increased risk for death at both 1 and 3 years (odds ratio for death at 1 year, 3.45 [95% CI, 2.1 - 5.6]; odds ratio for at death at 3 years, 2.91 [95% CI, 2.06 - 4.11]).

Echocardiogram findings were not significantly associated with mortality at 30 days or 1 year, but were at 3 years.

In an accompanying editorial, Leonardo Roever, MHS, from the Federal University of Uberlândia, Brazil, and colleagues say that the results of "this elegant and sophisticated statistical model" should be used to formally implement early mortality assessment and prevention standards in patients presenting with stroke, increased cardiac troponins, and structural heart disease.

This work was supported by National Institutes of Health, National Institute of Neurological Disorders and Stroke. The authors and editorialists have disclosed no relevant financial relationships.

Stroke. Published online April 5, 2017. Article abstract, Editorial extract

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