Scan can speed chest pain diagnosis in ER, study finds
A CT scan of the heart can quickly detect whether there are fatty blockages or pockets of rock-hard calcium in the arteries of the heart—clues that coronary artery disease may be the cause of the chest pain, according to research reported in the Feb. 27 issue of the Journal of the American College of Cardiology.
"The new 64-slice CT scanners give us amazing pictures of the heart," said James A. Goldstein, MD, FACC, Director of Research and Education in the Division of Cardiology at William Beaumont Hospital, Royal Oak, MI. "With this very simple outpatient scan, you can rapidly determine whether the arteries are normal or abnormal—and if they're abnormal, whether the disease is mild, moderate, or severe."
Those who get a clean bill of health can safely go home from the hospital without further testing. "As a physician, it's tremendously satisfying to tell an anxious patient, within about 30 minutes, that their heart and arteries are normal," Dr. Goldstein said.
Six million people in the U.S. annually seek ER treatment for chest pain. At least half have inconclusive early test results. Of these, about 65% are eventually found not to have suffered a heart attack—but not before racking up diagnostic costs totaling $10 billion to $12 billion annually. Even low-risk patients with no history of heart disease can spend 18 to 24 hours in the emergency room as doctors repeat the ECG and blood tests.
To assess whether a CT scan of the heart could make the evaluation of chest pain more efficient and less costly, researchers recruited 197 patients with heart attack-like chest pain but no history of heart disease. In all patients, the results of the ECG and the blood tests that detect heart damage were normal, both initially and after being repeated four hours later. Researchers then randomly assigned half of the patients to have a CT scan of the heart and the other half to a standard diagnostic plan, which included additional rounds of ECG and blood testing, plus a nuclear scan of the heart.
Patients with a clearly normal CTs or nuclear scans were allowed to go home immediately, and those with a clearly abnormal scan were sent to the cardiac catheterization laboratory for further, invasive testing. In the CT group, patients with uncertain test results—either because the images were not clear or because there was only a moderate amount of disease in the coronary arteries—also had a nuclear scan to help determine whether invasive testing would be needed.
CT alone was able to determine that heart disease was the cause of chest pain or reliably rule out that possibility in 75% of patients. The remaining 25% had a nuclear scan in addition to CT. The cost and the time it took to reach a diagnosis were significantly lower in the CT group. Costs averaged $1,586 for patients who had a CT scan, as compared to $1,872 for patients who had a standard diagnostic evaluation (p<0.001). Similarly, the time it took to make a diagnosis averaged 3.4 hours with CT, as compared to 15 hours with the standard diagnostic approach (p<0.001).
"CT angiography has produced very impressive images of the coronary arteries without the need for catheterization, but where, when and how to use this information is uncertain," said Anthony N. DeMaria, MD, Editor-in-Chief of JACC. "These data demonstrate a potential application of CT angiography for the rapid assessment of chest pain in the emergency room. However, it must be acknowledged that the patient population was limited, confined to low risk individuals based upon initial evaluation, and that the primary benefit was in detecting abnormalities sooner and more inexpensively, but not more accurately. The effect of the earlier diagnosis upon outcome also remains to be determined."
A large randomized controlled trial will put CT to a demanding test. Dubbed CT-STAT, the Coronary Computed Tomography for Systematic Triage of Acute Chest Pain Patients to Treatment trial will involve 750 low-risk patients evaluated for heart attack-like chest pain at 15 hospitals across the United States. Patient recruitment will begin soon.
CT does have limitations, Dr. Goldstein said. For example, if a patient is already known to have coronary artery disease, CT is less helpful. That's because it can't determine whether a moderate blockage is substantial enough to interfere with blood flow to the heart, thereby causing chest pain. In addition, it often fails to produce clear images in very obese patients—although this barrier may fall as manufacturers work on new imaging methods.
Another concern is radiation exposure, noted Pim J. de Feyter, M.D., Ph.D., University Hospital Rotterdam, the Netherlands, in an accompanying editorial in the Feb. 27 issue of JACC. This is particularly true for patients with moderate arterial narrowings or unclear CT images. They receive one dose of radiation during CT scanning, a second dose of radiation during follow-up nuclear scanning, and in some cases, a third dose during cardiac catheterization.
"If multislice CT does not give a definitive diagnosis, alternative diagnostic strategies that avoid radiation exposure … should be investigated," Dr. de Feyter said.
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