WEDNESDAY, March 10, 2010 (HealthDay News) -- If you walk into an emergency room complaining of chest pains, the odds are high that you will end up having cardiac catheterization, where a thin wire is snaked into your heart to determine whether a blood vessel is totally or partially blocked.
But if you do have the invasive procedure, the odds are even higher -- nearly two to one -- that it will show no significant blockage, a new study finds.
"To me, what this says is that we need to re-evaluate how we work these patients up from start to finish," said Dr. Manesh Patel, assistant professor of medicine at Duke University, and lead author of a report in the March 11 issue of the New England Journal of Medicine.
More than 10 million Americans each year experience chest pains that can lead to cardiac catheterization, Patel estimated.
He and his colleagues looked at data on nearly 400,000 people with no known heart disease who had cardiac catheterization at 663 U.S. hospitals between January 2004 and April 2008. Of those, just 37.6 percent had obstructed coronary arteries -- slightly less than the 39.2 percent in whom no significant artery blockage was found.
Catheterization is called an invasive procedure because it requires that something be inserted into the body, which always carries a degree of risk. So doctors usually want to do a less risky noninvasive procedure, such as a stress test, to decide whether catheterization is advisable.
But while five of every six people in the study -- 83.9 percent -- did have a noninvasive test before catheterization, those tests did not have an enormous predictive value. Artery blockage was found in 41 percent of those who had noninvasive testing before catheterization and 35 percent of those who didn't.
"We don't know that this finding substantiated the kind of noninvasive test we should be using," Patel said. "We don't know what the patterns are, and we need more research."
It's not enough to simply say that cardiac catheterization is overused, he said. "What we want to do is use it more efficiently," Patel said, "to determine the features that indicate catheterization is necessary."
The study "points out a problem, but is not suggesting a solution," he said. A national data bank on catheterization may provide information pointing toward a solution, as may some randomized trials that are now underway, Patel noted.
One of those trials, in which Patel is participating, is comparing the results of routine stress testing with computerized tomography angiography, which gives a three-dimensional view of the heart arteries, in 10,000 people.
The cardiac catheterization study results are not surprising, said Dr. Andrew Einstein, an assistant professor of clinical medicine at Columbia University Medical Center, whose specialty is cardiac imaging. An old rule of thumb is that one-third of cardiac catheterizations will show no artery blockage, he noted.
"This study does provide stronger data than we have ever had in the past," Einstein said. "The important takeaway message is that better risk stratification is needed to inform decisions about catheterization. If we have a good strategy, people will not be referred as often for these invasive procedures."
And cost is an inevitable issue in making those decisions, he added. "The cost of a diagnostic catheterization at our hospital is $2,600," Einstein said.
The why and how of cardiac catheterization are explained by the U.S. National Library of Medicine.