New Troponin Tests Diagnose Heart Attacks Faster and More Accurately

When a patient checks into a hospital with symptoms of a heart attack, an accurate diagnosis can take up to 12 hours. But high-sensitivity cardiac troponin tests promise to change that. Physicians at the Massachusetts General Hospital Heart Center are at the forefront of an effort to adopt this new method of testing and define how it can best be used to benefit patients.

The History of Troponin Testing

Troponins are proteins that are released into the bloodstream when the heart muscle has been damaged. Emergency rooms have used troponin testing in the past to pinpoint patients with acute myocardial infarction (MI), which is more commonly known as a heart attack. However, conventional tests took so long to produce results that they did little to help guide physicians to an appropriate treatment.

The first high-sensitivity test was approved by the U.S. Food and Drug Administration in early 2017, although they were available previously outside the U.S. with good success. According to James Januzzi, MD, a cardiologist at Mass General, this revolutionized the use of troponin tests in diagnosis.

"These tests are able to detect even minute amounts of heart injury at a much earlier time than the older troponin assays. Because of this, we can diagnose or exclude a heart attack in as little as one hour," Dr. Januzzi says.

Improving Error Rates

One reason the new high-sensitivity troponin tests are so useful is that they can detect a heart injury even when only a tiny amount of troponin is present. In fact, the tests are so sensitive that their error rate is under 10%.

"Because of this, highly sensitive troponins can identify 25% more MIs than previous troponin assays, and can do it even faster," says Dr. Januzzi. That means patients can start their treatments right away, which could help prevent further heart damage.

But the ultrahigh sensitivity of these new tests also presents a risky flipside because they may detect heart injuries that were caused by something other than MI and require a different type of treatment. Dr. Januzzi and his team have been educating physicians on how to best use their clinical judgment when ordering and interpreting the results of high-sensitivity cardiac troponin testing.

The training focuses on helping clinicians understand that not all patients who test positive for troponin are suffering from heart attacks. When the testing turns up low concentrations of troponin, it may be a sign that the heart injury was caused by another factor like chronic high blood pressure, kidney disease or diabetes.

Faster Testing

Physicians at Mass General's Emergency Department and Heart Center are now using an accelerated protocol for diagnosing MI. The protocol instructs physicians to perform a high-sensitivity troponin test within an hour of admission. Patients who are determined to be suffering from a heart attack can be triaged for treatment within that hour, while those who don't test positive for MI are quickly given an appropriate treatment plan.

Under the new protocol, patients with ambiguous results are retested after three hours. Even with a second test, patients who haven't experienced a heart attack are often discharged more quickly than they might have been using earlier troponin tests.

Other Uses for High-Sensitivity Cardiac Troponin Tests

The Mass General Heart Center is now evaluating the potential for high-sensitivity cardiac troponin testing to be used in nonemergency settings. In early 2018, for example, researchers from the center participated in an international study looking at the value of troponin testing in patients with chronic heart failure. After examining 10 studies involving more than 9,000 patients, they concluded that the testing can predict which patients face the highest risk of mortality or hospitalization due to heart problems.

The new troponin tests may also help physicians identify coronary artery disease and improve the monitoring of patients who have already been diagnosed and are considered to be stable.

All in all, these new tests "may help to support clinical decision-making well beyond the concept of acute MI," Dr. Januzzi says.