Blood Test Could Detect Heart Attack Early

In preliminary lab studies, the test produced results in just five minutes and had a 99 percent accuracy rate, according to the researchers.

Their study is scheduled to appear in the August 1 print issue of the Journal of Proteome Research, a peer-reviewed journal of the American Chemical Society, the world's largest scientific society.

The new test is a dramatic improvement over conventional blood tests that can take several hours to become positive following a heart attack and are only 50 to 70 percent accurate upon hospital admission, the researchers say. It uses mass spectrometry to measure two markers in blood serum that are associated with the earliest stages of a heart attack, which can be difficult to diagnose.

It could help reduce unnecessary hospital stays by patients whose chest pain is caused by other conditions, such as gallstones and severe indigestion, which can mimic heart attack pain, the researchers say. Of the estimated three to five million Americans visiting emergency rooms each year with chest pain, only about one in five of these actually have a heart attack, according to the Food and Drug Administration.

The test also shows promise for identifying heart attacks that can occur without the classic symptom of chest pain or the classic abnormal electrocardiogram (ECG). Some heart attack patients come to the hospital with ambiguous symptoms, including indigestion, dizziness, shortness of breath, or pain in other parts of the body, such as the neck, jaw or arm.

"I think this test will dramatically improve the ability of physicians to rapidly and unambiguously diagnose heart attacks," says John Marshall, Ph.D., chief investigator for the study and a consultant with Syn.X Pharma Inc., in Toronto, Ontario, which is developing the test. If all goes well in future studies, the test could be available in clinics in three to five years, he says.

Researchers have been trying for years to develop better diagnostic tests for heart attacks. In conjunction with an ECG, current tests screen for a variety of proteins found in the blood that are known to be associated with heart attacks. These proteins include creatine kinase, myoglobin, and most recently, troponin. All are indicators that a heart attack is taking place and that heart cells have begun to die.

In the current study, Mashall and his associates focused on two proteins found in blood serum that appear to reflect the early onset of a heart attack, when heart cells are being deprived of oxygen but have not yet begun to die. One of the proteins, C3f, was discovered as a heart attack marker for the first time and is known to be associated with inflammation. The other is a well-known protein called fibrinogen peptide A, which is involved in the clotting process.

The presence of these proteins in the blood signals the beginning of a cascade of inflammatory and clotting events that eventually lead to a full-blown heart attack, the researchers say.

Like other markers, the mere presence of these early markers is not a definitive diagnosis of heart attack, but serves as a diagnostic aid to be used in combination with other diagnostic criteria for determining if a heart attack is in progress, they say.

Identifying heart attacks at an earlier stage is a key to improving patient outcome, as it permits available treatments, such as clot-busters and angioplasty, to begin earlier, adds cardiologist and study co-author Eric Stanton, M.D., an associate professor of medicine at McMaster University in Hamilton, Ontario.

A key to the success of the new diagnostic test will be access to mass spectrometry, says Stanton. The technology, which can identify tiny blood proteins by their unique electrochemical fingerprint, is generally only available in research settings. That may change in the near future, as the technology becomes more affordable and more practical for use in clinical settings, such as emergency rooms, he says.

Several companies are already experimenting with mass spectral tests for diagnosing other diseases, including cancer and diabetes. In the future, the now bulky technology may be reduced to the size of a laptop computer that is capable of evaluating a patient's complete disease profile based on a single drop of blood — all in a fraction of the time it would take to get conventional test results — Stanton predicts.

In addition to helping diagnose which patients are having a heart attack, the newly identified markers may contribute to a further understanding of how a heart attack progresses and may help identify new therapeutic targets for improving its treatment and outcome, Stanton says.