ROME – Functional, noninvasive cardiac imaging using cardiovascular MR or myocardial perfusion scintigraphy was significantly better than was a current and well regarded guideline-based approach to identifying patients with chest pain and suspected coronary artery disease who could safely avoid angiography, thereby cutting the rate of unnecessary angiography by about 75%.
Following the guideline formula adopted by the British National Institute for Health and Care Excellence (NICE) resulted in a 29% rate of unnecessary angiography compared with rates of 7.5% using cardiovascular MR (CMR) and 7.1% using myocardial perfusion scintigraphy (MPS) in a multicenter randomized trial with 1,202 patients, John P. Greenwood, MBChB, said at the annual congress of the European Society of Cardiology.
This universal use of a functional, noninvasive imaging strategy to guide angiography resulted in no significant penalty of missed coronary disease or subsequent coronary events. The rate of positive angiography findings was 12% among the 240 patients managed according to the NICE guidelines, 10% among 481 patients screened by CMR, and 9% among the 481 patients screened using MPS, reported Dr. Greenwood, professor of cardiology at the University of Leeds (England). The rate of major adverse coronary events after 12 months of follow-up were 3% following the NICE protocol and 4% when screening by CMR or with MPS.
Concurrently with Dr. Greenwood’s report, the findings from the Clinical Evaluation of Magnetic Resonance Imaging in Coronary Heart Disease 2 (CE-MARC2) study appeared in an article online (JAMA. 2016 Aug 29. doi: 10.1001/jama.2016.12680).
“We showed that a functional test with CMR or MPS can reduce the rate of unnecessary coronary angiography. Cutting unnecessary angiography is really important to patients, and it may also cost effective,” he said, but cautioned that a formal cost analysis of the options tested in this study is still being run.
The NICE guidelines manage patients with chest pain that could be angina by their pretest probability of having coronary artery disease (CAD), and at the time the study was designed the NICE guidelines, issued in 2010, provided the most up-to-date expert guidance on how to triage these patients. The study enrolled patients with a pretest probability for CAD of 10%-90%; collectively their average probability was 50%. The patients participated in the study at one of six U.K. centers during November 2012 to March 2015. The average age was 56 years.
MPS is “probably the noninvasive imaging approach most commonly used worldwide to detect coronary ischemia,” Dr. Greenwood said. But he led an earlier study that showed that CMR, using a gadolinium-based tracing agent, works even better than MPS (in this study single photon emission CT) to predict a patient’s risk for major cardiac events. He said this superiority is probably because of the greater spatial resolution with CMR.
“The higher spatial resolution of CMR, about 5- to 10-fold greater that MPS, is less likely to produce false negative results,” he said in an interview. “We showed that CMR has higher diagnostic accuracy, is a better prognosticator, and is more cost effective” than MPS. Dr. Greenwood attributed the similar performance of CMR and MPS in CE-MARC2 to the study’s design, which led to fewer patients undergoing each of the two imaging methods and made CE-MARC2 underpowered to discern a difference in specificity. In his earlier study, which included 752 patients who underwent examination with both CMR and MPS, the negative predictive value of CMR was 91% compared with 79% with MPS.
CMR uses conventional MR machines, is now widely available, and is being widely used today as a first-line test in the United Kingdom and Europe, he added.
Dr. Greenwood believes that in his new study functional imaging outperformed the NICE guidelines because the pretest models used in the guidelines “tend to overestimate risk,” the factor that produces angiography overuse.
His report included two additional analyses that assessed the impact of CMR and MPS in the subgroup of patients with a high pretest probability for CAD, 61%-90%, and in the subgroup with a low pretest probability, 10%-29%. Among the patients with a high likelihood for CAD the two functional imaging methods cut the rate of unnecessary angiography by 95%, a statistically significant difference. Among those with a low likelihood functional imaging cut the rate 56%, a difference that did not reach statistical significance.
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