CorE 64: 64-slice CT sees cardiovascular disease as well as cardiac cath
The Coronary Artery Evaluation Using 64-Row Multidetector Computed Tomography Angiography (CorE 64) trial findings were presented today at the American Heart Association’s annual Scientific Sessions in Orlando, Fla. The study marks the first time an imaging study was presented on AHA’s late-breaking clinical trials agenda. The nine-center, seven-country multicenter study was sponsored by Toshiba Inc. and Bracco.
“In patients with suspected coronary artery disease and calcium scores less than 600, 64-row MDCTA can assess the presence of significant CAD [coronary artery disease] and the likelihood physicians will refer for coronary revascularization,” Miller told the AHA audience of several hundred. "This study is the first step to realizing the full potential of CT imaging in predicting coronary artery disease, and these scans complement the arsenal of diagnostic tests available to physicians to prevent heart attacks.
“Hopefully, we can avoid catheterization methods with patients with normal coronary arteries,” Miller told a press conference this morning.
According to the study, as many as 25 percent of the 1.3 million cardiac catheterization performed each year in the United States may not be necessary. The latest estimates from the AHA show that one in five deaths in the United States each year is due to coronary heart disease (653,000 deaths in 2004), including 157,000 who die from heart attack. More than a quarter million Americans undergo coronary bypass surgery each year, according to Johns Hopkins.
The CorE 64 study showed that, on average, 91 percent of patients with blockages were detected by 64-slice CT and that the scans were able to diagnose 83 percent of patients without blockages. More than 98 percent of the coronary arteries as small as 1.5mm in diameter could be seen using 64-slice CT. Results showed that the test had good diagnostic ability for detecting blockages >50 percent occlusive (sensitivity 0.85 and specificity 0.90, AUC 0.93). Also, CT showed a similar diagnostic ability to cardiac cath in its ability to identify patients who were felt to have severe enough disease to be referred for angioplasty or bypass surgery, though it was less able to determine which specific vessel of the heart was blocked, compared with cardiac cath.
In the study that began in September 2005 and ended in January 2007, investigators selected 291 men and women over the age of 40 (median age: 59; 74 percent male; median BMI: 27; prevalence of disease: 56 percent) with suspected CAD who were already scheduled to have cardiac catheterization to check for blocked arteries. In all, 868 vessels were analyzed. Each patient underwent a 64-slice CT scan prior to catheterization. Participants were then monitored through regular check-ups to identify who developed or did not develop CAD and who required subsequent bypass surgery or did not need surgery.
After the first year of monitoring, to continue annually until 2009, researchers found that results from CT matched up 90 percent of the time with results from invasive catheterization in detecting patients with blockages. In other measures, researchers found that CT scans were 83 percent to 90 percent accurate, while tests using older, 16-slice CT scans were in some instances only 20 percent to 30 percent as precise.
The study also suggests that the new scanners, which are four times quicker than the more widely used 16-CT, may be a good alternative to cardiac stress testing, which evaluates heart function by measuring the effects of hard exercising. Exercise stress testing generally cannot safely be performed on the weak and elderly.
"Use of 64-slice CT scans will dramatically improve our ability to detect and treat people with suspected coronary disease and chest pain much earlier in their disease," said João Lima, MD, senior investigator of the CorE 64 team. "Cardiac catheterization is still the gold standard for evaluating clogged arteries, but our results show that this test could easily be the best backup or alternative."
Miller said 64-slice allows physicians to measure blockages in blood vessels as small as 1.5 millimeters in diameter. Sixteen-slice CT scanners, she said, are best suited for looking inside bigger arteries, those ranging in diameter from 2 millimeters to 4.5 millimeters, and to calculate the amount of calcium buildup in the arteries, also a predictor of the degree of blockage, "but now we have a more advanced test that actually measures the amount and volume of blockage present."
She said 16-slice is not as powerful since it is unable to image as much as 25 percent of the smaller blood vessels that branch out from the heart's main arteries. However, 64-slice picks up as much as 98 percent of the heart's arterial network (and lacks good images for only 2 percent.)
Miller pointed out that early detection of blockages is critical to pre-empting a heart attack, allowing time for drug therapy, angioplasty or heart bypass surgery to be used to keep arteries open. "And we no longer need to wait until a patient is stabilized before performing this diagnostic test, as no anesthetic is needed for CT scanning," Miller said.
Miller also told the audience today she believed the study results could be reproduced at other facilities if proper ACC/AHA guidelines for training and quality assurance were implemented.
According to researchers, nearly 5,000 64-slice CT scanners are installed worldwide, and about four-fifths of the centers are equipped to perform and read cardiac CTs.
Besides Lima and Miller, other Johns Hopkins researchers involved in this study were Armin Zadeh, MD; Ilan Gottlieb, MD: Edward Shapiro, MD: Albert Lardo, PhD; David Bush, MD; Christopher Cox, PhD; and Jeffrey Brinker, MD. Additional investigators included Carolos E. Rochitte, from the University of Sao Paolo in Brazil; Marc Dewey, from Humbolt University in Charite, Germany; Hiroyuki Niinuma, from Iwate Medical University in Japan; Narinder Paul, from the University of Toronto in Canada; Melvin Clouse, from Beth Israel Deaconess Hospital in Boston, Mass.; John Hoe, from Mount Elizabeth Hospital of Singapore; and Albert de Roos, from Leiden University in the Netherlands.