Performing high-sensitivity cardiac troponin I at presentation in patients with suspected acute coronary syndrome (ACS) can rule out myocardial infarction (MI) quickly and accurately, according to a new study published in Lancet. This strategy could help emergency department physicians identify low-risk patients suitable for discharge, shorten ED wait times, reduce unnecessary hospitalizations, decrease costs — and, most importantly, alleviate patient anxiety about the possibility of having had a heart attack.

Each year, according to Hospitals and Health Networks, more than 7 million people visit emergency departments in the United States with a chief complaint of chest pain that may or may not indicate a heart attack. While many of these patients may be suitable for direct discharge from the ED, the procedures currently in use cannot rule out MI at presentation and must rely on serial troponin tests.

Since most heart attacks involve discomfort in the center or left side of the chest, chest pain is usually a frightening experience for patients. ED physicians admit about half of these patients to the hospital for further observation, serial troponin testing or treatment for suspected acute coronary syndrome, or ask that the patient wait for the result of testing.

This means patients presenting with ACS symptoms often experience needless hospital admission or long waits in the emergency department, which can add a great deal of stress to a patient who may have had a heart attack.

According to international guidelines, cardiac troponin concentrations above the 99th percentile should be used for the diagnosis of myocardial infarction. The researchers found that high-sensitivity cardiac troponin assays with high precision at low concentrations could detect vastly lower levels of troponin than previous tests.

Led by a team of researchers from University of Edinburgh, the investigators performed a cohort study of 6,304 consecutively enrolled patients with suspected ACS admitted to four hospitals in Scotland. The scientists wanted to know if the detection of troponin levels less than 5 ng/L would be predictive that the patient was not at high risk for MI.

Using a high-sensitivity cardiac troponin I assay, the scientists measured plasma troponin concentrations upon initial presentation to the ED. The researchers then evaluated the negative predictive value of a range of troponin concentrations for the primary outcome of index MI, or subsequent MI or cardiac death at 30 days post-presentation.

The results showed that a troponin threshold of less than 5 ng/L identified 61 percent of patients at a low risk for MI, with a negative predictive value of 99.6 percent. During a follow-up one year later, the researchers found that those same patients still had a threefold lower risk of MI and cardiac death as compared to those with troponin levels of 5 ng/L or higher.

In the interpretation of their results, the researchers noted that low plasma troponin concentrations could identify those two-thirds of patients presenting with chest pain who are at low risk for cardiac events. This early identification method would allow ED doctors to discharge patients home sooner and more safely than ever before. Prompt discharge substantially reduces unnecessary hospital admissions and can present major benefits for both patients and the healthcare providers who serve them.