Protein test sets new standard for heart attack detection

November 14, 2001

ANAHEIM, Calif., Nov. 14 - A blood test that detects elevated protein levels associated with dying heart cells could dramatically increase the number of individuals with chest pain who are diagnosed with heart attack, according to research presented today at the American Heart Association's Scientific Sessions 2001 conference.

The new test further supports efforts to redefine heart attack, researchers say.

According to National Center for Health Statistics estimates, almost 1.5 million people are hospitalized each year with unstable angina (chest pain) and an electrocardiogram irregularity called non-ST segment elevation heart attack, which is indicative of a "mild" heart attack. Both are life-threatening conditions that require urgent care and hospitalization.

The American College of Cardiology and the European Society of Cardiology have recently recommended that any elevation of troponin - a protein produced by dying heart cells - should be considered a heart attack. However, determining the effects of this new standard are difficult, because of the number of different troponin tests and different elevation cutoff points used, says Michael Kontos, M.D., assistant professor of internal medicine and cardiology at Virginia Commonwealth University in Richmond.

Researchers evaluated different blood test markers in 4,117 patients with chest pain admitted into the hospital's coronary care unit. They compared the predictive value of the standard heart attack marker, the enzyme creatine kinase (CK-MB), to a form of troponin known as troponin I. Both are used to diagnose heart attack in people having chest pain.

CK-MB is released not only by damaged heart tissue but other damaged tissues, which can cloud results. Furthermore, when a patient suffers a mild heart attack, CK-MB levels may remain normal, making diagnosis difficult. Troponin, however, is a protein produced by dying heart cells, and prior studies have found that its presence may indicate that heart damage has occurred.

The overall incidence of heart attack when CK-MB was used as the marker was 8.3 percent. Researchers also compared the cutoff points of troponin in two levels. When the upper reference value for troponin I was used, the number of heart attack patients increased by a relative 22 percent. In contrast, when the lower limit of detectability for troponin I was used, the number of patients with heart attack increased by a relative 160 percent, says Kontos.

"Evaluating patients with symptoms suggestive of a heart attack can be difficult when an electrocardiogram is inconclusive," says Kontos. "Over a four-year period, we have found troponin at lower levels is more sensitive for diagnosis of heart attack than CK-MB alone in such patients.

"The troponin test has significant predictive value, suggesting that the number of mild heart attacks in such patients is far greater than we have been able to recognize in the past," he says.

According to Kontos, the manufacturers of the many available blood tests for troponin use higher cutoff points than the researchers found for confirming heart attack.

"Our study provides a more sensitive method for identifying patients with heart damage," he says. "Depending on the diagnostic value used for the tests, the troponin standard could more than double the number of patients who have had a non-ST elevation heart attack."

Normally the level of troponin I in the blood is very low, and is usually undetectable. It increases substantially within several hours (on average four to six hours) of heart muscle damage. It peaks at 10 to 24 hours and can be detected for a week or more after.

Several studies have identified a measurable relationship between cardiac troponin levels and long-term outcome after an episode of chest discomfort. They suggest that these tests may especially help evaluate levels of risk.

"In other words, it's possible that the results of a troponin test could be used to identify people at risk for later, serious heart problems," says Kontos.

Troponin tests have been increasingly used throughout hospitals in the United States because of their recognized high sensitivity for identifying small amounts of heart damage. A revised definition of heart attack could have significant implications on health care since patients who in the past would have been labeled as having unstable angina will now be identified as having had a heart attack, says Kontos. It could make it difficult to compare heart attack rates, outcomes and treatment rates between physicians and hospitals.

"The use of troponin tests is being incorporated into several new American Heart Association/American College of Cardiology guidelines that deal with professional recommendations for the management of patients with heart disease," says Sidney Smith, M.D., chief science officer of the American Heart Association. "We believe that the improved sensitivity of this test will allow us to better identify and risk-stratify patients for early therapy and thus improve outcomes."
-end-
The study's co-authors are: M. Lucie Fritz; F. Philip Anderson, Ph.D.; Joseph P. Ornato, M.D.; James L. Tatum, M.D.; and Robert L. Jesse, M.D., Ph.D.

CONTACT:
For information November 10 - 14,
call: Darcy Spitz or Bridgette McNeill
at the Hilton Anaheim Hotel
(714) 251-5801

NR01-1350 (Sessions/Kontos)

Abstract 3346

American Heart Association

Related Heart Attack Articles from Brightsurf:

Top Science Tip Sheet on heart failure, heart muscle cells, heart attack and atrial fibrillation results
Newly discovered pathway may have potential for treating heart failure - New research model helps predict heart muscle cells' impact on heart function after injury - New mass spectrometry approach generates libraries of glycans in human heart tissue - Understanding heart damage after heart attack and treatment may provide clues for prevention - Understanding atrial fibrillation's effects on heart cells may help find treatments - New research may lead to therapy for heart failure caused by ICI cancer medication

Molecular imaging identifies link between heart and kidney inflammation after heart attack
Whole body positron emission tomography (PET) has, for the first time, illustrated the existence of inter-organ communication between the heart and kidneys via the immune system following acute myocardial infarction.

Muscle protein abundant in the heart plays key role in blood clotting during heart attack
A prevalent heart protein known as cardiac myosin, which is released into the body when a person suffers a heart attack, can cause blood to thicken or clot--worsening damage to heart tissue, a new study shows.

New target identified for repairing the heart after heart attack
An immune cell is shown for the first time to be involved in creating the scar that repairs the heart after damage.

Heart cells respond to heart attack and increase the chance of survival
The heart of humans and mice does not completely recover after a heart attack.

A simple method to improve heart-attack repair using stem cell-derived heart muscle cells
The heart cannot regenerate muscle after a heart attack, and this can lead to lethal heart failure.

Mount Sinai discovers placental stem cells that can regenerate heart after heart attack
Study identifies new stem cell type that can significantly improve cardiac function.

Fixing a broken heart: Exploring new ways to heal damage after a heart attack
The days immediately following a heart attack are critical for survivors' longevity and long-term healing of tissue.

Heart patch could limit muscle damage in heart attack aftermath
Guided by computer simulations, an international team of researchers has developed an adhesive patch that can provide support for damaged heart tissue, potentially reducing the stretching of heart muscle that's common after a heart attack.

How the heart sends an SOS signal to bone marrow cells after a heart attack
Exosomes are key to the SOS signal that the heart muscle sends out after a heart attack.

Read More: Heart Attack News and Heart Attack Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.