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March 6, 2006

A University of Michigan Health Minute update on important health issues.

Should you get a high-tech 'snapshot' of your heart?

If your risk of heart disease is high, or other tests aren't clear, the answer may be yes, U-M experts say

64-slice CT scans may spot problems before a heart attack, but more research needed

ANN ARBOR, MI – These days, hospitals everywhere are bragging about their new high-tech heart scanners, which can take high-speed “snapshots” of the heart and look for potential problems. Oprah Winfrey had her heart scanned, and so did Matt Lauer of the Today show — and both showed off their scans on national TV.

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Experts agree that this new technology, called 64-slice CT scanning, is poised to revolutionize heart care, by catching problems early without an invasive test.

So, should you get your heart checked out this way? It depends on who you are, say University of Michigan Cardiovascular Center experts who have been scanning hearts for years and were among the first in the nation to use a 64-slice CT scanner.

People whose family history and current health status put them at high risk of heart disease are probably much more likely to benefit from the scan than others, they say, because they can catch problems early and make changes to their diet, exercise habits and medication use to prevent a heart attack.

People with heart-related symptoms like chest pain or shortness of breath who have gotten abnormal or unclear results from a stress test might benefit from having the scan instead of an invasive exam. And patients who have gone to an emergency room because of sudden symptoms might benefit from a high-speed CT scan to see if they’re having a heart attack, stroke or rupture of a major blood vessel.

But mostly healthy people with few heart risks, and people who have already had a heart attack, probably don’t need the scan. More research is needed on exactly how the scans should be used to diagnose disease and guide treatment — research that’s going on right now at U-M and other places. Until more studies are done, in fact, many insurance companies aren’t covering the cost of the scan for most people.

But hopes are high that 64-slice CT scans will eventually prove to be useful in many patients, says Kim Eagle, M.D., co-director of the U-M Cardiovascular Center.

“The ability to image the coronary arteries, or blood vessels around the heart, using a non-invasive method has been something that we’ve been seeking for decades,” he explains. “For many years, we’ve relied on identification of risk factors, like diabetes, smoking and high cholesterol, and used stress-testing and electrocardiograms to try to find coronary artery disease before it hurts a patient.” But those tests often miss the kinds of blockages that are likely to form blood clots that can cause heart attacks.

Another kind of test, called a heart catheterization or angiogram, can reveal those kinds of blockages — but to see them doctors have to snake a thin tube through the patient’s bloodstream and up toward the heart. This kind of invasive exam is expensive and carries a small but very real risk of complication such as stroke, so it’s best used on people who have already had a heart attack or severe chest pain, or who have major blockages that need to be propped open to keep the blood flowing through their blood vessels.

Earlier 16-slice and 32-slice CT scanners, and modified CT scanners designed specifically for heart scanning, yielded some information about blockages in coronary arteries. But they couldn’t make crystal-clear images of the coronary arteries and heart because of the heart’s constant movement.

That’s why the 64-slice CT scanners hold such promise, says Ella Kazerooni, M.D., director of thoracic imaging at the U-M Health System and a specialist in making medical images of the heart.

“Cardiac CT angiography differs from most traditional CT in that the pictures we take are timed to when the heart is moving and when it’s not,” she explains. “The latest generation of CT scanners allows us to scan so fast that we essentially freeze the heart’s motion, and therefore can look at these small, moving coronary arteries. It’s the most difficult structure in the body to image, and I think we’ve finally conquered it.”

The images can reveal not only whether there are clogged areas, but also what’s causing the blockages: old, healed-over areas of damage called plaques, or new inflamed ones that could rupture and lead to a heart attack or stroke.

Using powerful computers, sophisticated software and their advanced training to analyze the CT images, doctors can even analyze “movies” of the heart, looking for any problems with the muscle. They can also spot tiny defects in the heart that might have gone undetected since a person was born, and that might raise their risk of a problem later on.

In some cases, including several at U-M, CT heart scans have revealed problems with patients’ lungs or blood vessels outside the heart. Eagle recalls one patient who went in for a heart scan, and was found to have a small cancer in her lung and was able to get treatment. In a study, Kazerooni and her colleagues found that non-heart problems are found on a large number of heart-CT scans. This makes it important for different kinds of doctors to work together on analyzing scans, she says.

After years of scanning hearts with 16-slice CT machines, U-M was one of the first U.S. hospitals to buy a 64-slice CT scanner. By this fall U-M will have five, including one in the emergency room.

Kazerooni and others are leading several studies that use the scanners, including a study that compares the scans with the more established tests that are done via heart catheterization. One study, led by cardiologist Mauro Moscucci, M.D., is using America’s first facility that combines a 64-slice CT scanner and cardiac catheterization equipment — with the goal of learning how the two technologies can work together to diagnose and guide treatment in certain heart patients.

Even as these studies take place, U-M heart specialists are recommending that some of their high-risk patients have the 64-slice scan done. If the scans show blockages, the patients might be able to avoid a heart attack or surgery later by taking medicines to lower their cholesterol and blood pressure, as well as making changes in diet, exercise and stress management. And, says Eagle, such patients can also learn to recognize heart attack warning signs, so they can get help quickly.

Eagle, who had a family history of premature heart disease, had his own heart scanned — which revealed early-stage problems that have prompted him to make changes in his own life. “If we use this technology in people without symptoms to find early disease that we can affect with lifestyle and medications, then I think it will be a major advancement for our society,” he says.

One U-M patient’s heart-scan story:
Dick CroakeDick Croake, a U-M staff member, knew in the back of his mind that he was probably at high risk of developing heart disease. His father died of a heart attack at the age of 63, after having been in heart failure for several years. And Croake had occasionally had high blood pressure readings and high cholesterol levels — factors that, combined with his family history, put him at high risk.

After hearing a doctor discuss his own brush with heart disease, Croake asked his doctor for a heart test. First, he had a stress test, which made ultrasound images of his heart while he exercised on a treadmill. That test showed subtle but real abnormalities, so his doctor referred him to U-M’s CT scanner. The scans showed that the problem was greater than the stress test had indicated, but not serious enough to need immediate treatment. Croake started taking a cholesterol-lowering drug in addition to his blood pressure medication. He also received a “just in case” vial of nitroglycerin and advice on what to do if he experienced symptoms.

Armed with this knowledge, and a better awareness of his risk, Croake knew just what to do when he woke up in the middle of the night a month later and felt short of breath. At the ER, he told the staff that he had been diagnosed with coronary artery disease — which helped them zero in on his heart.

While this episode turned out not to be a heart attack, but rather a warning for a heart attack, Croake and his doctors decided it was time for him to have a cardiac catheterization and angioplasty to open a blocked artery. A stent, or tiny tube-shaped scaffold, was inserted to keep the artery open.

“I’m glad that I had the test, and I would encourage anyone who has risk factors in their background to seek it,” he says, “either to have the peace of mind that there’s nothing the matter, or to find out that there is and to address it before there’s some cardiac event that’s a real problem or even fatal.”

About CT scans and coronary artery disease (clogged heart arteries):

  • In the last year, many American hospitals have installed 64-slice CT scanners and have begun using them to scan hearts and other organs. Because they are so new, research is still examining who could benefit most from having a scan, and who should have other tests.
  • 64-slice CT scanners are able to make images so quickly that they can take a picture of the heart and the coronary arteries surrounding it, despite the heart’s constant motion. This allows doctors to see blockages inside blood vessels that are caused by a buildup of plaque — a condition called coronary artery disease or atherosclerosis.
  • Unlike other tests that detect heart problems, 64-slice CT scanners make high-quality images without going inside the body in any way — except for an injection of a dye that can make the image even clearer. However, since CT scans are made using intense X-rays, patients receive a radiation dose equal to several chest X-rays.
  • People whose parents or close blood relatives had heart disease or a heart attack at an early age, but who haven’t had heart problems themselves, may be good candidates for a 64-slice CT scan, because they may be able to find out early about any problems.
  • People who have a number of other “risk factors” for heart disease, such as diabetes, high cholesterol, high blood pressure, smoking, lack of exercise, overweight, may also benefit from a scan, especially if they also have a family history.
  • Abnormal or unclear results on a stress test, which is a kind of non-invasive heart test often performed using a treadmill, may also make a person a good candidate for a 64-slice scan.  

For information on heart disease diagnosis and treatment at the U-M, contact the U-M Cardiovascular Center toll-free at 888-287-1082. Please note that 64-slice CT scans are available only with a referral from a physician, and only to patients meeting certain criteria.

Find out more on the web at: U-M Cardiovascular Center: www.med.umich.edu/cvc

 

Written by: Kara Gavin

 

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