New Heart Scan May Speed up Diagnosis with Less Radiation

New imaging technology appears to provide faster, more accurate heart scans for both viewing blood vessels in the heart and measuring blood supply to the heart muscle, while exposing patients to less radiation.

Researchers reported their findings online August 23, 2011, in the journal Circulation: Cardiovascular Imaging, a journal of the American Heart Association. In preliminary tests from a small trial of 39 patients, computerized tomography (CT) scans called second-generation, 128-slice, dual-source Flash CT captured faster images of the entire heart allowing clinicians to better visualize artery blockages and reduced blood flow through the heart. This was accomplished using one-tenth of the radiation of current CT scans, the standard test for diagnosing and pinpointing the location of heart disease.

The CT scan uses a high-pitch Flash CT scan technique, which enables an ultrafast scan time. A contrast agent and vasodilatator is injected into the patient’s blood vessels to help highlight certain areas. “The new exam is faster and more convenient for the patient,” said Gudrun M. Feuchtner, MD, a professor in the department of radiology at the Innsbruck Medical University (Austria), and a study coauthor.

The new technology captures images of the entire heart in less than 0.3 seconds--within one heartbeat--as compared to 6 seconds and several heartbeats for traditional CT scans. For accuracy, the new scan was compared to cardiac magnetic resonance imaging (MRI), and invasive angiogram, which involves sliding a catheter through an artery in the groin or arm to the heart. An angiogram, and sometimes MRI, requires contrast dye.

Compared to cardiac MRI, 78% to 95% of the time the new CT accurately identified restricted blood flow and correctly ruled it out 84% to 94% of the time. Compared to invasive angiography, the new CT scanner had 90% accuracy in detecting significant blockages. The new CT scanner’s accuracy improved to 95% when added to CT perfusion--a scan taken after using contrast dye.

The scan proved especially useful in patients with advanced heart disease or diabetic patients who reported no symptoms, but were found to have areas of poor coronary blood flow, according to Dr. Feuchtner. Because diabetics may have nerve damage, they may not always experience the chest pains that typically accompany reduced blood flow to the heart. “Those patients would not immediately seek a cardiologist, but would have a poor prognosis,” he stated.

The study findings can also help to plan heart surgery more accurately, according to Dr. Andre Plass, a coauthor and cardiac surgeon from University Hospital Zurich (Switzerland).

Moreover, the new technology answers two questions with one scan: whether the blood vessels of the heart are narrowed and whether there is reduced blood flow. “This can have important implications for cost savings and efficiency as two studies are done in one setting,” said Ricardo C. Cury, MD, coauthor of the study and chairman of radiology at Baptist Health of South Florida (Miami, USA).

Larger studies are needed, however, according to the investigators, before the new technology is widely used.

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Innsbruck Medical University