320-Detector CT Imaging as Effective as Invasive Tests to Evaluate Heart Blockages

An ultrafast, 320-detector computed tomography (CT) scanner that shows both anatomy within coronary arteries and blood flow can effectively decide which patients require or do not require an invasive procedure to identify coronary blockages, according to an international study. The researchers reported that their findings could have the potential to save millions of people worldwide from having an unnecessary cardiac catheterization.

The study, known as CORE 320, involved 381 patients at 16 hospitals in eight countries. An article on the findings was published online November 19, 2013, in the European Heart Journal. In the study, participants were evaluated with a 320-detector CT and typically used tests that are now widely used. The researchers reported that 91% of those in whom the CT scan ruled out blockages would not have needed invasive treatment such as bypass surgery or stenting. Therefore, those patients, none of whom had a history of coronary artery disease, could have avoided invasive tests because for them the CT scan was just as effective in ascertaining who would be a good candidate for revascularization as the traditional testing.

“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,” said Joao A. C. Lima, MD, senior author of the study and a professor of medicine and radiology at the Johns Hopkins University School of Medicine (Baltimore, MD, USA). “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.”

According to Dr. Lima, the study findings, would apply to individuals suffering from chest pain but not a heart attack based on electrocardiogram (ECG) and other indications. Many people in that setting are sent to a cardiac catheterization laboratory for additional assessment with angiography, an invasive test to look for blockages in the coronary arteries using dye and special X-rays. Approximately 30% of patients 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, reported Dr. Lima.

The 381 patients who completed the study had traditional single-photon emission computed tomography (SPECT) imaging and invasive angiography. Dr. Lima reported that SPECT, a stress-type of test, shows reduced blood flow to the heart without indicating the number or specific location of blockages.

Study participants also had two types of tests with a noninvasive 320-detector CT scanner. In the first CT test, the scanner was used to see the anatomy of vessels to assess whether and where there were blockages. That test is known as CT angiography (CTA). Then, in a second CT test with the same machine, patients were given a medication that dilates blood vessels and increases blood flow to the heart in ways similar to what happens during a stress test. The second test is called CT perfusion (CTP).

“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,” stated lead author Carlos E. Rochitte, M.D., a cardiologist at the InCor Heart Institute, University of Sao Paulo Medical School (Brazil), “We were therefore able to correctly identify the patients who needed revascularization within 30 days of their evaluation.”

“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 Dr. Richard George, MD, an associate professor of medicine at the Johns Hopkins University School of Medicine, and a coauthor of the study. “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 Dr. George, who developed the CTP method with Lima.

The 320-detector CT provides a wide-ranging picture of the heart by making just one revolution around the body. The researchers noted that the two tests combined, CTA and CTP, still generate less radiation than a scan with the 64-detector CT scanner in widespread 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 Dr. Lima.

The researchers noted that they would continue to monitor the patients in the study for five years, searching for any heart-related events such as heart attacks, as well as hospital admissions, or procedures.

The study was sponsored by Toshiba Medical Systems Corp. (Tokyo, Japan).

Related Links:
Johns Hopkins University School of Medicine
InCor Heart Institute, University of São Paulo Medical School