Chest pain drives more than 5 million people to hospitals each year, out of fear that their excruciating symptoms signal a heart attack in progress.
Yet heart attacks, terrible as they are, will strike only about 1.1 million people this year, according to the American Heart Association. Moreover, among those patients who make it to emergency rooms, only about 10% turn out to have acute heart attacks.
For the vast majority of chest pain patients, something else, usually less life-threatening, is to blame. But ferreting out the exact cause is difficult and expensive. Sometimes the culprit is merely heartburn. Other times the pain is a sign of serious cardiac trouble, such as unstable angina, which if recognized and treated can avert a heart attack. For all the advances in medicine, doctors rely on a time-consuming process of elimination to make a definitive diagnosis when heart symptoms are equivocal, as they are most of the time.
Though the current standard of care, clinical elimination is far from foolproof: 2% to 8% of chest pain patients with heart attacks are sent home in error when they should have been treated.
But a set of new blood tests that can be performed in the emergency department in less than half an hour promises to dramatically speed up and sharpen the diagnostic process. Besides time, the tests could save lives and money by helping doctors more quickly separate those patients with heart attacks from those with less-serious conditions.
The cardiac tests measure biochemical markers that enter the blood stream in proportion to the amount of cardiac muscle damaged during a heart attack. When the heart is starved of oxygen by blocked coronary arteries, every minute without treatment means more damage.
The most popular of the new tests yields numerical results that can be tracked over time. If the markers rise together from readings taken over several hours, a heart attack has struck. Other patterns tip doctors to look for another problem.
"How quickly can you rule out that somebody is having a heart attack?" is the key question, according to James McCord, M.D., cardiology director of the chest pain unit at Henry Ford Hospital in Detroit. Only a few years ago, the answer used to be a day. Now the standard is nine hours, with some centers pushing the time down to six hours.
The diagnostic lag can hinder important treatment for patients with heart attacks, such as clot-busting drugs whose effectiveness depends on how quickly they can be administered. At the other extreme, prolonged delays can lead to precautionary, yet ultimately unnecessary, hospital admissions for patients who seem terribly ill but really aren't. Neither option is attractive to patients, payers or practitioners.
As a result many health systems, such as Henry Ford, which sees 500 chest pain patients per month, have responded to the thorny problem of managing these patients with specialized chest pain clinics.
By all accounts hospitals, with or without chest pain clinics, need more help to do the diagnostic job right. Happily, science marches on, and this relatively new batch of laboratory tests, some processed right inside the emergency department, promises to change the way heart attacks are diagnosed.
The most commonly consulted markers are cardiac troponin, myoglobin and creatine kinase, or CK-MB.
These tests have been available in some centralized labs for several years but haven't been widely used. One reason: time. Solving the urgent clinical problem of heart attack diagnosis requires quick results. Even the stat sections of many central labs sometimes can't provide results fast enough.
"There's no question that there is a need to improve turnaround time for cardiac market tests," says Alan Wu, director of clinical chemistry at 923-bed Hartford (Conn.) Hospital. "If the results are positive, you want to move that patient to the appropriate level of care as quickly as possible. If the results are not indicative of a heart attack, nobody wants to sit around in the ER waiting."
Recently a trio of companies has introduced cardiac marker tests that can be used on the clinical floor, rather than a central lab, to speed diagnosis.
Spectral Diagnostic of Toronto, Canada, makes qualitative tests. Dade Behring, of Glasgow, Del., and Biosite Diagnostics, of San Diego, make quantitative assays.
Preliminary results show that the tests can slash by hours the time to rule out a heart attack. At Henry Ford, preliminary results in 500 of 1,000 patients diagnosed with the aid of Biosite tests performed in the clinic show that heart attacks were ruled out in 3.2 hours, compared with 10.5 hours by traditional methods. The bedside cardiac tests cost about $25 per patient, compared with $15 when the tests are done in the central lab.
Though a cost-effectiveness study has yet to be completed, McCord says the tests can be valuable at busy chest pain centers, like his, which often face congestion when patient loads are high.
"We're already talking about how we'll implement this," he says.
To realize the potential benefits, though, administrators must grapple with higher direct costs for the point-of-care tests, nearly twice the cost of those performed on large analyzers in central labs. And, wherever the tests are performed, clinicians must integrate the data immediately into their decisionmaking rather than relegate them to patients' records after the fact.
"If a hospital doesn't use the information in real time," Hartford Hospital's Wu says, "then it won't demonstrate the savings and (the tests will be) unnecessary."