Calcium Scan of Arteries Helps Spot Big Trouble
WEDNESDAY July 29, 2009 -- Adding a scan for calcium in the heart arteries to a standard test of blood vessel function helps predict which people with known coronary disease are likely to develop serious problems, a new German study indicates.
"The combination of myocardial SPECT and coronary artery calcium scoring could help identify those who are at highest risk for subsequent fatal cardiac events in a long-term outcome," said study author Dr. Marcus Hacker, an associate professor of nuclear medicine at Ludwig Maximilians University in Munich. His report appears in the July 28 online edition of Radiology.
Single-photon emission computed tomography (SPECT) uses radioactive material to provide three-dimensional images of heart arteries. It is widely used to diagnose heart conditions. A calcium scan, also using radioactive material, measures the amount of calcium in the walls of heart arteries as another indicator of potential coronary problems and is not generally used for such diagnoses.
The study of 260 people with known heart disease, including some who had already suffered heart attacks, compared the five-year incidence of severe cardiac events and the need for bypass surgery with results from the two tests.
The results showed that the participants with calcium scores above a certain level were at highest risk of death or major problems and were more likely to have bypass operations. "A CAC [calcium] score greater than 400 offered incremental prognostic value over the scintigraphic [SPECT] scores alone," the journal report said.
The study results indicate that calcium scans could become common tests after diagnosis of heart disease, Hacker said. "We suggest a status scan for calculating the coronary artery calcium score in patients shortly after the diagnosis of coronary artery disease or in combination with a regular SPECT perfusion scan," he said.
The calcium scan results could help guide treatment, he explained. "Applying intensified medical therapy or shortened follow-up intervals in these patients could result in a major benefit in their outcome," Hacker said.
But he quickly added that the finding "has to be verified in prospective trials."
The study does not bear on a controversy about whether calcium scans should be used to screen healthy people for heart disease, Hacker said. "As the present study focused on patients with already known disease, there can be no conclusions drawn for a screening setting," he said.
But it is also difficult to decide whether to add calcium scans to the tests normally used after heart disease is diagnosed on the basis of this study, said Dr. Thomas G. Gerber, an associate professor of medicine and radiology at the Mayo Clinic.
It was a small study, Gerber said, and selection of the people in such a study can be an issue. "They seem to have done a good job of picking patients, but we are always cautious about patient selection," he said.
And the treatment goals for managing people with known heart disease are already clear, Gerber said.
"It is difficult to know where a calcium score would tell us something that would change our management of a patient," he said. "The calcium score only shows an increased risk. It doesn't tell us how we can modify risk other than by doing what we already should be doing, which is treating known risk factors."
It's clear that measures to control risk factors such as high blood pressure and obesity should be stricter in people with more severe heart disease, Gerber said. "Nobody knows if making those measures even more strict would make the outcome better," he said. "That stands to reason, but we just don't know. No one has shown how making decisions based on calcium content influences outcome. The studies to tell us how to use that information to decrease risk haven't been done yet."
The why and how of calcium scans are explained by the U.S. National Heart, Lung, and Blood Institute.
Posted: July 2009