ER bedside tests speed diagnosis, improve risk-assessment of individuals with chest pain

April 01, 2001

DALLAS, April 3 - Individuals with chest pain who have blood tests in the emergency room for multiple biochemical markers receive faster diagnosis and better risk assessment, according to a study in today's Circulation: Journal of the American Heart Association.

The study compared bedside testing for multiple markers of heart damage in the first hours upon arriving in the emergency department with standard testing for a single biochemical indicator, which involves sending blood samples to a laboratory. Researchers found that among individuals with chest pain, those at high risk of death were identified one hour faster on average with multiple-marker bedside testing.

Also, analyzing multiple blood markers over a six- to 24-hour period at bedside detected two to three times as many potentially high-risk individuals as analysis for a single marker done at a laboratory outside of the emergency department.

"Earlier and more accurate identification of high-risk individuals with chest pain could allow speedier, targeted use of medicines, such as anti-platelet therapy and beta-blockers, which could minimize muscle damage and other complications after a heart attack," says L. Kristin Newby, M.D., lead investigator of the study and assistant professor of cardiology at Duke University's Clinical Research Institute in Durham, North Carolina.

Each year more than 5 million individuals go to emergency rooms with chest discomfort, but only a fraction are actually having a heart attack, Newby says. Blood tests for three biochemical markers - creatine kinase MB (CK-MB), troponin I and myoglobin - can help diagnose early heart damage.

The study, called CHECKMATE, included 1,005 patients in six chest-pain units within emergency departments across the country. All participants had their blood drawn and evaluated with three different strategies - one marker in the site laboratory, two markers at bedside, or three markers at bedside. In the dual marker tests, researchers checked levels of CK-MB and troponin-I - the most commonly measured markers, while the triple marker tests, looked at those plus myoglobin.

Because patients arrive at the emergency departments at varying times after onset of chest pain and different biochemical markers are detectable at different times, it was proposed that testing with multi-marker strategies would improve early detection of high-risk patients.

"Testing for all three markers at the time the patient arrived in the emergency department detected all patients at increased risk for death within 30 days," Newby notes. "Testing for just one marker missed all of these high-risk patients."

Bedside multiple markers also more accurately identified patients at high risk for other major complications within 30 days. About 19 percent of those whom three-marker bedside testing identified as high risk died or had another heart attack within a month. The single-marker testing identified 13 percent. Only 3 percent identified by three-marker bedside testing as low-risk had such complications, while nearly 6 percent who were identified as low risk by single marker testing had them.

Patients at high risk in all the testing methods were more likely to be older, male, and to have diabetes, hypertension, prior chest-pain history, heart failure or kidney dysfunction.

Another important finding is that the marker test used least frequently in current evaluation of those with chest pain, may - in combination with the more widely used marker - give the most precise answer, says Newby.

Of the markers, the myoglobin is the least often examined by cardiologists in assessing chest pain. Although it is not specific for heart muscle damage, it has important benefits in assessing chest pain, according to Newby. Because elevations of myoglobin are detectable earlier than elevations of CK-MB or troponin, marker-positive patients who are at increased risk for death or other complications from a heart attack can be identified within one to three hours of symptom onset, while the other biochemical markers require a longer time period.

CK-MB measures one form of the enzyme creatine kinase. It is the most commonly used blood test to determine heart-muscle damage after a presumed heart attack. It rises above normal within four to six hours of heart attack onset.

Measuring levels of troponin I (cTNI), a protein in heart muscle, can also reveal whether heart muscle damage has occurred. Elevated troponin I can be detected within five to six hours of a heart attack onset. Troponin peaks 10 to 24 hours later, and usually stays above normal for a week or more.

"The study emphasizes the utility of myoglobin as an earlier indicator of muscle damage than the other two markers," says Newby, "and it shows the added value of myoglobin in combination with other markers tested at the bedside for accurately identifying high-risk patients from among those presenting to our emergency departments with chest pain. The potential benefits to patient care from routinely using such a multi-marker testing strategy are tremendous."
Study co-authors are Alan B. Storrow, M.D.; Brian Gibler, M.D.; J. Lee Garvey, M.D.; John F. Tucker, M.D.; Andrew L. Kaplan, M.D.; Donald H. Schreiber, M.D.; Robert H. Tuttle, M.S.P.H.; Steven E. McNulty M.S.; and E. Magnus Ohman, M.D.

CONTACT: For journal copies only,
please call: (214) 706-1396
For other information, call:
Carole Bullock: (214) 706-1279
Bridgette McNeill: (214) 706-1135

American Heart Association

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