Study: CT Scans Rule Out Heart Attacks Faster - @ JEMS.com


Study: CT Scans Rule Out Heart Attacks Faster


 
 

MARILYNN MARCHIONE | | Wednesday, November 18, 2009


ORLANDO, Fla. A CT scan a kind of super X-ray provides a faster, cheaper way to diagnose a heart attack when someone goes to the emergency room with chest pains, a new study suggests.

About 6 million people each year go to hospitals with chest pain, but only a small fraction are truly having a heart attack. CT scans are increasingly used to diagnose problems because they give a deep, detailed view inside the body. But they put out a lot of radiation, which may raise a person's chances of developing cancer.

Whether these scans are worth that risk is unknown. The new study suggests that for ruling out heart attacks in the emergency room, they just might be.

The research involved 749 chest pain sufferers at 16 big medical centers around the country. These were people who did not have clear signs of a heart attack from blood tests or EKGs, but doctors are afraid to send them home without more tests.

Between 4 percent and 13 percent of such patients will have a missed diagnosis of a heart attack, and up to one quarter of that group will die, said the new study's leader, Dr. Kavitha Chinnaiyan, a cardiologist at William Beaumont Hospital in suburban Detroit.

"One of the most common reasons for an emergency room physician to be sued is that they send a patient out and then they come back with a heart attack," said Dr. Sidney Smith, a former American Heart Association president from the University of North Carolina at Chapel Hill. "It is a big problem."

In the study, half of the patients were given CT scans and the rest, standard imaging tests with a radioactive dye. Of the CT patients, 82 percent were found to have clear arteries and were discharged immediately. In the other group, 89 percent were determined to have normal arteries and sent home.

The portion of patients who needed a definitive but invasive test angiography to see whether they should have an artery-opening balloon angioplasty procedure or bypass operation was the same 6 to 7 percent of each group.

The big difference was in cost and time.

CT scan patients were diagnosed in about three hours versus more than six for the others. Their testing also cost less $2,137 on average versus $3,458 for standard screening.

"It's equally safe, it's faster and it's cheaper," said Chinnaiyan, who has no financial ties to imaging companies. She reported results Wednesday at a heart association conference in Florida.

The study had partial support from Bayer Pharmaceuticals, which makes products used in heart imaging. A few doctors involved in the study have had research grants from Bayer or a firm that makes imaging equipment.

"These are promising results" for CT scanning, said Smith, who had no role in the work. "They were able to identify a certain group that did not need to be admitted."

Radiation remains a concern, though. A CT scan of the chest involves 10 to 15 millisieverts (a measure of dose) versus 0.01 to 0.15 for a regular chest X-ray, 3 for a mammogram and a mere 0.005 for a dental X-ray.

On the other hand, people with chest pain often are admitted to a hospital and then given repeated tests over a number of days that can add up to a high cumulative radiation dose.

"If you had a CT scan and it showed you were fine, you would not get any of that radiation," said Dr. Mariell Jessup of the University of Pennsylvania, who led the conference's scientific panel.

A more definitive picture of risks and benefits will come from a big study just getting under way, headed by Duke University's Dr. Pamela Douglas.

The $32.5 million federally funded study is the largest ever for heart imaging and the only one to look at how various imaging tests ultimately affect the rates of death, heart attack, stroke, hospitalization and other factors. It will enroll 10,000 people in the United States and Canada.

A big question, Douglas said, is: "As people get more and more radiation medically, are we adding up some new cases of cancer?"

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