Success of Bedside Markers Highlights Importance of Chest Pain Units in Identifying at-Risk Heart Disease Patients

Duke University Medical Center
Monday, 9 April 2001

Each year, more than 5 million Americans rush to emergency rooms with chest pain. While only 10 percent to 15 percent are actually having a heart attack, as many as 4 percent of those considered low-risk and sent home will actually be suffering a heart attack.

Although the current tools used by physicians to screen patients are getting better, cardiologists at Duke University Medical Center said they believe that special emergency care teams called chest pain units, a relatively new approach in the fight against heart disease, are the keys to finding new and better tools. Unfortunately, the researchers add, chest pain units are only available in one out of five U.S. acute care centers.

Chest pain units are usually located within emergency departments and are staffed 24 hours a day by emergency medicine specialists and supported by cardiologists who can quickly conduct the necessary tests to screen patients who are truly having a heart attack from those who are not.

Some of these tests involve measuring the levels of three different biochemical markers (creatine kinase MB, troponin I or T. myoglobin) that are released into the bloodstream by dying heart muscle.

In facilities without chest pain units, patients with suspected heart attacks or at high risk are usually admitted to a regular hospital room or coronary care unit to undergo further testing, which can take up to three days. Patients who test negative on one, or at most two, of the biochemical tests administered several times over six to nine hours in chest pain units are usually considered low-risk and sent home after just 12 to 24 hours.

The results of a recent study led by Duke researchers at six chest pain units demonstrate the units' ability to speed diagnosis of chest pain patients and to better determine their potential for future heart attacks. In the so-called CHECKMATE study, the Duke researchers proposed combining for the first time the use of all three of the markers and their rapid bedside analysis.

"Earlier and more accurate identification of high-risk patients with chest pain could allow speedier, targeted use of medicines, such as anti-platelet therapy or beta-blockers, which could minimize heart muscle damage and other complications," said Duke cardiologist and lead investigator, Dr. L. Kristin Newby.

The results of the 1,005-patient CHECKMATE trial, which were first presented last August at the 22nd annual congress of the European Society of Cardiology and were published Tuesday in the journal Circulation, clearly demonstrate that chest pain units using such testing could save lives and that more hospitals should open them, the researchers said.

CHECKMATE showed that using multimarker testing in chest pain units identified those patients at the highest risk of heart attack one hour earlier than standard approaches, and that this approach detected almost three times the number of potentially high-risk patients.

"These tests are very good at identifying heart muscle that is dying, but what we really need now are better ways of detecting muscle that is at risk, and therefore still salvageable," Newby said. "In order to make these advances, we must be able to get to patients as soon as they come into contact with the health care delivery system, which means the emergency departments."

Newby, who directs Duke's chest pain unit, cited an earlier Duke study which showed that the use of a single marker indicated that 90 percent of the 380 chest pain unit patients studied tested negative; however, two years later, 7 percent of those patients had died of a heart attack.

"Clearly then, within this group of chest pain patients determined to be at low risk of a heart attack there is a high-risk population," she explained. "The markers we have now -- which can only measure dying muscle -- are good, but they cannot identify these particular patients. Using multiple markers is an improvement, but we need to find new markers that will identify patients at risk before heart muscle starts dying."

To accomplish this, Newby and colleague Dr. Magnus Ohman said the creation of more chest pain units and other initiatives are crucial. Ohman was co-investigator of CHECKMATE and recently joined the faculty of the University of North Carolina at Chapel Hill as chief of the division of cardiology.

"We are rapidly approaching a crisis -- the prevalence of coronary artery disease is rising as the Baby Boomers are entering their 50s, and the ability of the health care system to handle them is declining," Ohman said. "These chest pain units represent an important avenue for best treating these patients."

The key to developing these units, according to Newby and Ohman, who together helped organize one of the nation's first such units at Duke in 1994, is close collaboration with their colleagues in the emergency department since this is usually where chest pain patients first encounter the health care system.

"Anything we can do in the emergency room to stratify chest pain patients will prevent us from sending people home with a high probability of dying," Ohman said.

Another novel approach, which begins in May, is a national initiative involving more than 400 hospitals. Participating centers will

gather data on how chest pain patients are being treated and their outcomes. The researchers also want to know if centers are following the latest guidelines set forth by the American Heart Association (AHA) and the American College of Cardiologists (ACC), which advocate for the chest pain unit approach.

The initiative, CRUSADE (Can Rapid risk stratification of Unstable angina patients Suppress ADverse outcomes with Early implementation of the ACC/AHA guidelines), will be coordinated by the Duke Clinical Research Institute. Ohman serves as one of its chairmen.

In CHECKMATE, the standard laboratory test conducted by the hospitals identified 44 patients at risk, with average time to detection of positive results of about three hours, but failed to identify any of the patients who died during the study. When researchers ran all three tests, 149 positive patients were detected in less than two hours and no high-risk patients were missed by the testing.

CHECKMATE was conducted at Duke; the University of Cincinnati; Carolinas Medical Center in Charlotte; St. Luke's Medical Center in Milwaukee, Wis.; Stanford University Medical Center in Palo Alto, Calif.; and St. Luke's Roosevelt Hospital in New York.

For more information, or to contact Duke University Medical Center, see their website at: www.mc.duke.edu