A reports on a study that highlights the safety issues involved in detecting coronary blockages:-
Noninvasive CT scans are nearly as accurate at imaging coronary artery blockages as conventional angiography and are much safer for many patients, according to researchers who published a study released recently in the New England Journal of Medicine.
.Angiograms are considered the gold standard for detecting blockages. But the procedure involves inserting a guide wire and catheter into the groin, threading them through the blood vessels to the heart and injecting a dye that allows the blockage to be seen in an X-ray.
Using a CT machine instead to make a three-dimensional image of the heart could eliminate the risks involved with traditional angiograms, including heavy bleeding, damage to blood vessels and even death, said Dr. Julie Miller, an interventional cardiologist at Johns Hopkins University School of Medicine in Baltimore and lead author of the study.
More than 1.2 million patients in the US undergo cardiac catheterisations each year, and 1-2 per cent of those cases result in complications, according to the American Heart Association. The National Center for Health Statistics at the Centers for Disease Control and Prevention estimates that about 25 people die each year as a result.
About 20 per cent to 30 per cent of those tests give patients a clean bill of health, and that means that hundreds of thousands of people are exposed to needless risk, Miller said. Many cardiologists see CT scans as a safer alternative because the scans are powerful enough to create a high-resolution image even when the contrast dye is administered by a simple intravenous line and thus more dilute.
Miller and her colleagues at nine hospitals in the US, Canada, Germany, Japan, Brazil, Singapore and the Netherlands identified 291 patients with symptoms of coronary artery disease who were candidates for traditional angiograms. Their median age was 59, and 74 per cent were men.
Before the patients had their angiograms, their hearts were imaged in 8.5 seconds with a 64-slice CT scanner made by Toshiba Medical Systems, which funded the study along with the National Institutes of Health and private foundations.
Two physicians examined each image and graded the degree of narrowing in 19 places in the main coronary arteries. Then the researchers compared the results from both procedures.
In the 163 patients with the highest degree of coronary artery disease — a narrowing of at least 50 per cent in at least one artery — the CT angiograms were 93 per cent as good as traditional angiograms, according to the study. Overall, the CT scans accurately identified 85 per cent of the patients who had the biggest blockages and 90 per cent of the patients who did not.
The researchers also found that 91 per cent of patients who were identified by the CT scans as having the most severe disease were correctly diagnosed, as were 83 per cent of patients whose scans did not reveal large blockages.
Two of the patients in the study had a reaction to the contrast dye used to perform the CT angiogram, and one patient died as a result of the conventional angiogram.
Dr. Matthew Budoff, director of cardiac CT at Harbor-UCLA Medical Center in Torrance, California, said the study confirmed results from his own research using a similar scanner made by General Electric Co. His study, funded by GE, was published this month in the Journal of the American College of Cardiology.
“It’s not quite but almost as good as an invasive angiogram,” said Budoff, who also receives speaking fees from GE. The CT test is faster and costs thousands of dollars less, and patients leave “with a Band-Aid and a bottle of water.”
“The benefits for many patients outweigh the risk of missing 1 per cent of disease,” he said.
But other doctors say that more data are needed to prove that CT angiograms are worthwhile, especially as a screening tool.
“What we really need is a study that compares cardiac CT to traditional ways of working up chest pain, like stress testing, and look at patient outcomes in both groups,” said Dr Rita Redberg, director of women’s cardiovascular services at University of California, San Francisco, Medical Center, who co-wrote a perspective article accompanying the study. “Without actual outcome data, we don’t know that this is going to help patients at all.”
Sources:Los Angeles Times
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