Tuesday, December 02, 2008

Cardiologists Debate Expensive Heart Scans

By RONI CARYN RABIN
02 dez 2008--Cardiologists have opened another front in the rancorous debate over expensive medical technologies, questioning the conclusions of a new study finding that high-resolution computer scans of the heart are almost as effective as conventional angiograms.
The debate reveals a deep rift among heart specialists over the use of 64-slice or CT angiography, which produces mesmerizing 3-D images of the heart and blood vessels.
CT scans are faster and less invasive than conventional angiograms, the gold standard for diagnosis and identification of blockages, but they expose patients to higher doses of radiation, which may increase the risk of cancer.
Angiograms, on the other hand, require insertion of a catheter through a blood vessel in the groin, a longer procedure that carries a risk of more immediate complications.
Many doctors have been quick to embrace CT technology, installing expensive scanners in their offices in order to help diagnose heart disease. Other physicians say the high-tech devices drive up health care costs and offer no proven benefits.
In the latest study, published last week in The New England Journal of Medicine, researchers assessed the accuracy of CT angiography in identifying blockages of 50 percent or greater in patients’ arteries. The multicenter international effort was paid for in part by Toshiba Medical Systems, a manufacturer of CT scanners, and many of the authors have financial ties to the company.
All of the patients in the study were at high risk for heart disease and had already been referred for conventional coronary angiography. They underwent both CT scans and conventional angiograms.
Of the 405 patients initially enrolled, 291 were included in the final analysis; nearly 100 patients were excluded because of calcium deposits that made it difficult to see inside the arteries. Most of the participants were men, with a median age of 59, and all had risk factors for heart disease like high cholesterol or being former smokers.
Slightly more than half of the patients had obstructive coronary artery disease, the researchers found, and CT heart scans were almost as accurate as conventional angiography in diagnosing the blockages.
Dr. Joao A. C. Lima, an associate professor of medicine at Johns Hopkins Medical School and an author of the study, suggested that CT angiography, or CTA, could be a good screening test for patients not known to have heart disease who develop sudden chest pain.
“You don’t want to perform an invasive procedure on everyone who has chest pain in the emergency room,” Dr. Lima said. “We’ve demonstrated that CTA can identify the patients who will need an invasive angiogram and those who will not.”
But in an accompanying commentary, Dr. Rita Redberg, a professor of medicine at the University of California, San Francisco, said the study had failed to address the most important question about CT scans: whether they improve patient outcomes.
“The last thing we needed was another study on diagnostic accuracy,” she said. “What I’m wondering is, if I use it for my patients, will my patients do better? We need evidence of benefit before we start using new technologies in widespread ways.”
In the study, CT scans misclassified the severity of the disease in 13 percent of patients, Dr. Redberg pointed out. The scans also missed 15 percent of patients with heart disease, detecting obstructions in only 85 percent of patients who had them, and correctly diagnosed only 90 percent of healthy patients as disease free.
A separate analysis by the study’s authors concluded that CT scans were just as good as conventional angiography at identifying patients who needed an intervention like angioplasty or bypass surgery.
Even the authors concluded that CT scans cannot replace angiograms for patients suspected of having heart disease.
“We never expected it to replace conventional angiography, which has been around for 50 years for a reason,” said Dr. Julie Miller, assistant professor of medicine at Johns Hopkins and a principal investigator of the study.
As a noninvasive diagnostic test, she added, “it’s very, very good, particularly given the low, low risk.”

No comments: