NEJM: CorE 64 study affirms 64-slice CT as cardiac cath alternative

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Heart scan with the Toshiba Aquilion 64-slice scanner. Image Source: Advanced Imaging Newport Coast  

In a development that researchers say could quell concerns about the value of costly CT scans to diagnose coronary artery blockages, the results from the CorE-64 study were published online Wednesday in the New England Journal of Medicine. The results confirm that 64-slice CT scans can correctly identify people with major blood vessel disease and that they are nearly as accurate as invasive coronary angiography. The initial findings from CorE-64 were presented at the 2007 annual American Heart Association’s (AHA) Scientific Sessions last November. The results released this week reflect the study’s updated data.

Investigators at nine medical centers reported that the faster, 64-slice CT scans were 93 percent as precise as invasive cardiac catheterization, and virtually 100 percent accurate in detecting people with at least one artery dangerously clogged by the buildup of cholesterol and plaque.

Each of the 291 men and women, all over the age of 40, selected to participate in the study were already scheduled to have cardiac catheterization to check for blocked arteries. Every participant had a 64-slice CT scan prior to catheterization and was then monitored through regular check-ups, starting in 2005 and set to continue through 2009, to identify who developed or did not develop any heart problems, who required subsequent bypass surgery or angioplasty and who did not need any procedure.

The authors wrote that the comparison of CT and catheterization results showed for the first time that they were equally useful in patients with heart attack symptoms, such as chest pain and shortness of breath, for predicting the need for cardiac bypass surgery or angioplasty. The researchers found that CT scans accurately predicted 84 percent of invasive procedures performed, and catheterization predicted 82 percent.

Lead study investigator and leader of angiographic research at Johns Hopkins, Julie Miller, MD, reported that the cost of the newer CT scans—approximately $700—compares favorably with that of current nuclear stress testing for reduced blood flow, in which radioactive dyes are used to detect arterial clogs, at nearly $1,000. Cardiac catheterization costs in excess of $1,500, according to the researchers.

More than a quarter-million Americans undergo coronary bypass surgery each year, and another 1.2 million people undergo angioplasty, according to the authors. Senior study investigator and Johns Hopkins cardiologist João Lima, MD, said that 64-slice CT scans, which take between five and 10 seconds to perform, are not a substitute for catheterization, but are “an alternative diagnostic tool” physicians can use to “rule in or rule out” coronary blockages when other, more indirect tests for reduced blood flow, such as cardiac stress testing, are unclear or unsafe for a particular patient. Cardiac catheterization takes between 30 minutes and 45 minutes to perform, and requires more than an hour for recovery.

Miller said that the disadvantages of using 64-slice CT are radiation exposure and the rare potential in someone having an allergic reaction or developing kidney problems from the contrast dyes. However, she cited improvements that cut the average amount of radiation exposure and time required for a CT scan to less than 20 mSv with 16-slice CT scanners (which took about 12 seconds to perform), on average, to less than 15 mSv with 64-CT devices (at close to six seconds) and less than 6 mSv with the 320-slice CT (at less than a second).

Lima noted that the team’s next steps are head-to-head comparison studies using either CT or nuclear stress testing. Included in the next analysis will be scans performed using the 320-slice CT.  

Toshiba provided funding support for the CorE-64 (Coronary Artery Evaluation using 64-slice Multidetector CT) study, which used its Aquilion 64-multidetector CT scanner. The researchers noted that Siemens Healthcare, Philips Healthcare and GE Healthcare manufacture similar devices.