Penn study finds cardiac scan accurately assesses heart-attack risk

A noninvasive scan that looks inside cardiac arteries can rapidly and reliably rule out the possibility of a heart attack among many emergency-room patients complaining of chest pain, according to a study led by University of Pennsylvania researchers.

The findings provide the strongest evidence to date that "CT angiography" could relieve a diagnostic dilemma - how to efficiently distinguish patients who can safely be sent home from those who should stay in the hospital.

About eight million annual ER visits are for chest pain. Hospitals spend billions of dollars testing and observing these patients, even though 85 percent turn out to have unrelated causes for their pain, such as muscle strain, pneumonia, or indigestion.

CT angiography shows whether arteries have clogged enough to trigger a heart attack, providing information that used to require an invasive, time-consuming procedure called a catheterization.

"We have spent the past 30 years trying to find a simple test that will tell patients, right now, 'It's not your heart,' " said Penn emergency medicine physician Judd Hollander, senior author of the study. CT angiography "is far and away the best test to do that."

The study, simultaneously published in the New England Journal of Medicine and presented this week at the American College of Cardiology's annual conference, found that compared with usual care, CT angiography reduced the time that most patients spent in the hospital, while improving detection of those who actually had dangerously clogged arteries.

Another large CT angiography study presented this week at the conference had similar findings. It was led by researchers at Massachusetts General Hospital and has not yet been published.

"In Boston, hospital emergency rooms are really crowded, as I'm sure they are in Philadelphia," said James Udelson, a Tufts University cardiologist who was a coauthor of the study. "It's a waste of time and resources" to keep chest-pain patients for observation when many could safely be sent home.

The Penn study involved 1,370 chest-pain sufferers who went to five medical center ERs.

These patients - all over age 30 with no known heart disease - were at low to moderate risk of a heart attack. Yet current guidelines say that such patients should spend 12 to 24 hours in the hospital, repeatedly undergoing blood tests and electrocardiograms, and possibly an exercise stress test, to rule out cardiac problems.

The study randomly assigned a third of the patients to receive this standard care, while the rest underwent CT angiography, a computer-enhanced X-ray technology that has been widely available for about six years.

Cardiac catheterization remains the gold standard for assessing vessel blockages, but it requires that a tube be threaded through a major artery to the heart.

Patients whose cardiac CT scans were "negative" - that is, they had less than 50 percent narrowing of key arteries - were sent home because studies have shown the chance of a heart attack over the next 30 days is remote, under 1 percent.

Indeed, CT scans proved to be as safe as usual care for those with minimal narrowing; there were no heart attacks in either group during the monthlong follow-up.

But the negative CT-scan patients were twice as likely to go home from the ER without hospital admission (50 percent compared with 23 percent who had usual care), and spent half as much total time in the hospital (12 vs. 25 hours).

Among those whose CT scans revealed serious narrowing, 4 percent wound up undergoing cardiac catheterization, and 1 percent suffered heart attacks or death - the same as in the usual care group.

Three percent of CT patients underwent blood-vessel repair surgeries, compared with 1 percent who had usual care. The researchers attributed this to the fact that CT scans detect narrowing that is missed with exercise stress tests.

"A lot of people were waiting for a paper like this with enough patients to show that if you send patients home after a negative CT, they will be safe," said lead author Harold Litt, Penn's chief of cardiovascular imaging.

Litt is part of a panel that is revising expert guidelines for evaluating chest-pain patients.

CT angiography exposes patients to radiation, so some experts are not ready to say it should replace usual care.

Another question is whether it would cut costs. While Penn researchers believe it would, the study led by Boston researchers found it was a wash.

"Both of these studies . . . are very good," said Paul Schoenhagen, cardiovascular imaging specialist at Cleveland Clinic in Ohio. "The [Penn] study shows the CT-based approach is safe, so for selected (low-risk) patients, it is a diagnostic option."

Doctors at the Hospital of the University of Pennsylvania talk about a noninvasive cardiac CT scan that can quickly and accurately rule out a heart attack. www.philly.com/ctscanEndText

at 215-854-2720 or mmccullough@phillynews.com.