Reed Miller

August 29, 2012

August 28, 2012 (Munich, Germany) — Noninvasive computed tomography (CT) perfusion imaging added to CT angiography accurately identifies flow-limiting coronary lesions that need to be treated, results of the CORE320 trial show.

Here today at the European Society of Cardiology 2012 Congress, Dr João AC Lima (Johns Hopkins University, Baltimore, MD) presented results of the 381-patient, 16-center trial, which showed that stress CT myocardial perfusion analysis (CTP) significantly improves the diagnostic power of rest CT angiography (CTA) alone. The study also showed that the CTA+CTP strategy has about the same power to identify patients who need revascularization within 30 days as the current standard strategy of invasive angiography plus a single photon-emission computed tomography (SPECT) myocardial perfusion imaging (MPI) test.

Lima explained that the potential advantage of the CT-based approach is that it can obtain information on myocardial perfusion and coronary flow in two scans about 10 minutes apart and is noninvasive.

All patients in the study had been referred for an invasive angiogram to investigate suspected or known coronary artery disease (CAD), but all patients underwent a rest CTA, stress CTP, and SPECT-MPI test in addition to the invasive angiogram. Invasive angiography alone identified apparently obstructive coronary disease in 59% of patients, but adding the SPECT-MPI information reduced that number to 38%.

The accuracy of the CTA+CTP approach was measured as the area under the receiver-operating-characteristic curve. When 50% greater stenosis on invasive angiography was set as the reference standard for a flow-limiting stenosis, the accuracy of the CTA+CTP approach for detecting flow-limiting CAD was 0.87 on a per-patient basis. When the standard was >70% stenosis, the accuracy of the CTA+CTP approach was 0.89.

Commenting on the trial, Dr Gerald Maurer (Wiener Krankenanstaltenverbund, Vienna, Austria) said, "The results are very straightforward" but provoke several questions about CT perfusion testing that it is hoped will be answered in new studies in the coming years. These questions include: Who should have this test? Will this change the practice of conducting noninvasive tests prior to invasive testing? And who, if anyone, should go directly to invasive angiography based on clinical information alone? He added that the cost-effectiveness of the CTA+CTP approach will have to be assessed.

"We also have to remember that stress CTP is an additional study after CT angiography that requires additional radiation and contrast administration," Maurer said. "This might be a particular issue when you use not the state-of-the-art 320-slice CT scanner but something that is more widely available, such as a 64-slice scanner."

Earlier at the ESC congress, Dr James Min (Cedars-Sinai Medical Center, Los Angeles, CA) presented results from the Determination of Fractional Flow Reserve by Anatomic Computed Tomographic Angiography (DeFACTO) study, which showed that fractional flow reserve data derived noninvasively from CT images (FFRCT) improves the accuracy of CT in identifying flow-limiting lesions. Flow-limiting lesions were also the target of the CTA+CTP tests in CORE320, so comparison of the two approaches is natural, but Min expects FFRCT and CTA+CTP to emerge as complementary rather than competing technologies. He told heartwire that CTA+CTP may work best for patients with angina due to myocardial-perfusion problems that cannot be traced to distinct coronary lesions.

A major advantage of FFRCT is that it can discriminate flow-limiting lesions from nonobstructive lesions with a single CT scan, while CTA+CTP requires two scans, taking more time and exposing the patient to more radiation and contrast--although it remains to be seen if that is a significant safety concern, he said. Also, the same computer technology that allows FFR measurement from a noninvasive scan may soon allow doctors to run a computer simulation that will show how stenting a particular vessel segment will improve perfusion, Min said.

The utility of both methods will no doubt become much clearer with the completion of more trials and registries in the coming years, he added.

Lima has received grants or research support from Toshiba, which sponsored CORE320, as well as Bracco Diagnostics and the National Institutes of Health. Min reports receiving research support from GE Healthcare and Philips Medical.