Study finds promise in heart scan

Hopkins report says diagnosis by CT nearly as accurate as catheter

November 06, 2007|By Chris Emery and Stephanie Desmon | Chris Emery and Stephanie Desmon,SUN REPORTERS

Computed tomography is nearly as effective as the invasive and expensive surgical methods typically used to diagnose coronary blockages, according to new research by Johns Hopkins cardiologists.

The CT scans are almost as reliable and accurate as cardiac catheters - the current standard of practice - in evaluating chest pains and other serious heart symptoms, the researchers said yesterday at the American Heart Association's annual conference in Orlando, Fla.

"This is a good way to actually see the blockages without having to do the invasive procedure," said Dr. Julie Miller, who led the study at Hopkins.

The scientists said widespread use of heart scans could reduce catheterizations by at least 25 percent. But other doctors disagreed; they warned that expanding the use of CT scans was premature and might expose patients to X-rays unnecessarily.

At the same meeting, a separate Hopkins group reported positive findings in another heart-related medical technology - defibrillators mounted in public places.

They found that public access to the devices - which shock the hearts of people in cardiac arrest - saves hundreds of lives every year, even when the equipment is used by untrained bystanders.

The study on CT scans was led by Miller, a Hopkins cardiologist who said the team of researchers from nine medical centers in seven countries was the first to demonstrate on a large scale that a scanning technology typically used on other parts of the body can be applied to the heart - an organ difficult to take pictures of because it is in constant motion.

"Many cardiologists don't believe this type of technology works," Miller said in an interview from Florida. "We've shown here in a very rigorous fashion that the diagnostic ability of CT scans is very good."

Widespread use of heart CT scans - essentially high-quality, three-dimensional X-rays - could reduce the need for catheterizations to diagnose heart blockages, she said.

About 40,000 diagnostic catheterizations were performed in Maryland hospitals in 2006, according to the Maryland Health Care Commission.

Catheterization, in which doctors insert a thin tube into a blood vessel in the groin area and thread it up to the heart and its arteries, would still be required to perform balloon angioplasty or to insert a stent, should either be required.

Both techniques are used to unblock clogged arteries without open-heart surgery.

There is a slight risk in inserting a catheter, which can cause discomfort, bleeding or, in rare cases, more serious complications. A catheterization also costs about four times as much as a CT scan, Miller said.

The relatively new but widely available CT procedure used in the study is a "64-slice CT scan."

As X-rays pass through the body, digitized signals or "slices" are reconstructed for a precise picture. These advanced scanners can measure blockages in blood vessels as small as 1.5 millimeters in diameter, the doctors said.

Critics, however, said CT scans need more thorough testing before they're put to broader use in finding heart blockages.

Dr. Michael Lauer, a cardiologist with the National Heart, Lung and Blood Institute, said research should show that CT scans are not only as good at finding blockages as catheters, but that they also save more lives.

He said doctors would be more willing to send patients for CT scans, which might be less invasive than catheterizations but carry their own risks.

"One big concern is radiation," he said. "There is the risk the radiation could cause cancer."

He urged other cardiologists to take a cautious approach. "I'm not against technology," he said. "I'm against it being prematurely introduced when it hasn't been adequately tested."

Dr. David Zimrin, director of the cardiac catheterization lab at the University of Maryland Medical Center, said that from a medical standpoint, he will be happy when CT scans replace some diagnostic catheterizations, but he worries that doctors might become too quick to refer patients for CT scans - costing the health care system more in the long run.

"It'll be used much, much, much, much more than diagnostic catheterization," he said.

The Hopkins-led study was conducted on 291 men and women over age 40 who were scheduled to undergo a cardiac catheterization to check their arteries for blockages - the most frequent trigger for a heart attack.

Each patient underwent the CT scan before receiving the catheter. They were then monitored through regular checkups to see who developed coronary artery disease and who required bypass surgery to open new blood supply routes to the heart.

After the first year, researchers found that in locating blockages, the results of the CT scan matched up 90 percent of the time with results from the more invasive procedure. Researchers plan to monitor these patients annually through 2009.

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