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Advanced CT Imaging Proves Just as Precise as Invasive Tests for Heart Blockages

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Based on an international study, an ultrafast, 320-detector computed tomography (CT) scanner that displays both anatomy within coronary arteries and blood flow can accurately pick out which people require, or dont require, an invasive procedure to classify coronary blockages.

The researchers suggest that their discoveries may be able to save millions of people worldwide from undergoing unnecessary cardiac catheterization.

The study, referred to as CORE 320, included 381 patients at 16 hospitals in eight different countries. An article on the results was published online by the European Heart Journal on Nov. 19, 2013.

In the study, participants were assessed with a 320-detector CT and standard tests that are widely applied today. The researchers say 91 percent of those in whom the CT scan ruled out blockages would not have needed invasive treatment such as stenting or bypass surgery. Therefore, those patients, none of whom had a history of coronary artery disease, could have circumvented invasive tests because for them the CT scan was just as precise in determining who would be an eligible candidate for revascularization as the standard tests.

"Ours is the first prospective, multicenter study to examine the diagnostic accuracy of CT for assessing blockages in blood vessels and determining which of those blockages may be preventing the heart from getting adequate blood flow. We found an excellent correlation in results when we compared the 320-detector CT testing with the traditional means of assessment using a stress test with imaging and cardiac catheterization, said senior author of the study and a professor of medicine and radiology at the Johns Hopkins University School of Medicine, Joao A. C. Lima, M.D.

The study discoveries, noted Lima, would apply to people who have chest pain but not a heart attack based on EKG and other supplemental evidence. Many people in those circumstances are sent to a cardiac catheterization laboratory for further observation with angiography, an invasive test that searches for blockages in the coronary arteries using dye and special X-rays.

About 30 percent of people who have such catheterization are found to have minimal disease or no blockage requiring an intervention to open the vessel with a stent or bypass the vessel through surgery, said Lima.

The 381 patients who underwent the study had conventional single-photon emission computed tomorgraphy (SPECT) tests and invasive angiography. According to Lima SPECT, a stress test with imaging, demonstrates reduced blood flow to the heart without signifying the number or specific location of blockages.

Study participants also had two types of tests with a noninvasive 320-detector CT scanner. For the first CT test, the scanner was utilized to view the anatomy of vessels to determine whether and where there were blockages. This test is known as CTA, in which the "A" stands for angiography.

For the second CT test with the same system, patients were provided a drug that dilates blood vessels and increases blood flow to the heart in ways similar to what occurs during a stress test. This second test is called CTP, with the "P" standing for perfusion.

"We found that the 320-detector CT scanner allowed us to see the anatomy of the blockages and determine whether the blockages were causing a lack of perfusion to the heart. We were therefore able to correctly identify the patients who needed revascularization within 30 days of their evaluation, said cardiologist at the Heart Institute (InCor), University of So Paulo Medical School, in Brazil and lead author of the study, Carlos E. Rochitte, M.D.

"Many patients are sent for an angioplasty when they may not need it. Our ultimate goal is to have more certainty about which patients having chest pain, without evidence of a heart attack, need an invasive procedure to open an arterial blockage, said cardiologist and associate professor of medicine at the Johns Hopkins University School of Medicine and a co-author of the study, Richard George, M.D.

"The CTP test added significant information about the patients'conditions and boosted our ability to identify those whose blockages were severe enough to reduce blood flow to the heart," added George, who helped develop the CTP testing method with Lima.

The 320-detector CT offers a fully-rounded image of the heart by making just one circular movement around the body. The researchers say the two tests combined, CTA and CTP, still generate less radiation than a scan with the 64-detector CT scanner in frequent use today.

"In our study, the amount of radiation exposure to patients from the two 320-detector CT tests was half the amount they received as a result of the traditional evaluation methods, the angiogram and nuclear medicine stress test combined," said Lima.

As of now the researchers say they will continue to follow the patients in the study for a five year period, looking for any adverse heart-related events such as heart attacks, as well as hospital admissions, procedures or operations.

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