CT scans found to be safe, accurate
Study says they can replace angiograms
Thursday, November 27, 2008
By Karen Kaplan, Los Angeles Times
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 today 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 U.S. undergo cardiac catheterizations each year, and 1 percent to 2 percent 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 of the procedure.
About 20 percent to 30 percent of those tests give patients a clean bill of health, and that means that hundreds of thousands of people are exposed to needless risk, Dr. 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.
Dr. Miller and her colleagues at nine hospitals in the U.S., 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 percent 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 percent in at least one artery -- the CT angiograms were 93 percent as good as traditional angiograms, according to the study. Overall, the CT scans accurately identified 85 percent of the patients who had the biggest blockages and 90 percent of the patients who did not.
The researchers also found that 91 percent of patients who were identified by the CT scans as having the most severe disease were correctly diagnosed, as were 83 percent of patients whose scans did not reveal large blockages.
Computed Tomography of the Chest (CHEST CT Scan)
Definition of the Procedure:
Computed Tomography :
an imaging method by which the lungs are scanned in successive layers by a narrow beam x-ray, a computer print out is obtained of the absorption values on the tissues in the plane that is being scanned
Purpose of Procedure:
>used in assessing hilar and mediastinal disease
>used to define pulmonary nodules, small tumors adjacent to pleural surfaces or spine
>an important tool in staging of lung cancer with the additional use of contrast material, CT also makes it possible to distinguish vascular from non-vascular structures, which is particularly important in distinguishing lymph nodes and masses from vascular structures
Preparation of the Patient:
> Remove metallic objects from chest
> Elicit history of allergies if contrast material will be used
> Ensure adequate renal function if contrast material will be used
Procedure:
> Must remain absolutely still during the procedure
> Time is approximately 20 mins if without contrast medium; 60 mins if with contract medium
> Sedation if unable to remain still
> Nothing per orem 4-6 hrs if contrast medium is used.
> Observe for allergic reaction to iodinated contrast material
Chest CT Scan procedure
