MR-INFORM Evaluates Stress-Perfusion Imaging to Guide Management of Stable CAD
March 17, 2017—Findings from the MR-INFORM study of stress-perfusion imaging to guide the management of patients with stable coronary artery disease (CAD) were presented by Eike C. Nagel, MD, in a Featured Clinical Research session at ACC.17, the American College of Cardiology's 66th annual scientific session in Washington, DC. MR-INFORM was sponsored by Guy’s and St. Thomas’ Hospital and King’s College London in London, United Kingdom. In September 2012, the design and rationale of MR-INFORM were explicated by Shazia T. Hussain, MD, et al in Journal of Cardiovascular Magnetic Resonance.
The study was summarized on behalf of the ACC by Dharam J. Kumbhani, MD, and reviewed by Deepak Bhatt, MD.
As reported by the ACC, the MR-INFORM trial sought to assess the utility of MR-based perfusion imaging compared with invasive angiography and fractional flow reserve (FFR) among patients with stable angina on optimal medical therapy (OMT). The findings showed that MR-based perfusion-guided management of patients with stable angina is noninferior compared with invasive angiography and FFR for major adverse cardiovascular events (MACE) at 1 year.
In the study, the investigators randomly assigned patients in a 1:1 ratio to either invasive angiography plus FFR (n = 464) or MR perfusion imaging (n = 454). In the FFR arm, invasive angiography was performed in all patients. FFR was recommended in all arteries > 2.5 mm with a stenosis of 40% to 95%. If FFR was < 0.8 mm, revascularization via percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG) was recommended.
MR perfusion was performed with a 1.5 T scanner using cine imaging. If transmural defect or subendocardial defect was present in more than two segments or was found in two adjacent slices, angiography with the aim of revascularization was recommended. All patients received OMT.
The mean age of study patients was 62 years, 28% of the patients were women, 27% had diabetes, and 13% had known CAD. Inclusion criteria included stable angina (Canadian Cardiovascular Society [CCS] class 2–3) and either two or more risk factors (smoking, diabetes, hypertension, hyperlipidemia, positive family history) or positive exercise treadmill test.
Exclusion criteria for the study included contraindication to MR or adenosine, atrial fibrillation or frequent ectopic beats, ejection fraction < 30%, CCS class 4, New York Heart Association class III or IV, previous CABG, PCI within the previous 6 months, estimated glomerular filtration rate < 30 mL/min/1.73 m2, the unablity to lie supine for 60 minutes, and/or medical instability
For the primary endpoint, the MR-INFORM investigators reported the following outcomes for FFR versus MR: 1-year MACE rates (3.9% vs 3.3%; P = .62), death (0.22% vs 0.89%), myocardial infarction (1.7% vs 1.8%), and repeat revascularization (1.9% vs 0.7%). Secondary outcomes included negative angiography (35.6% vs 8.1%), only 49.6% of MR patients needed invasive angiography, and revascularization during index event (44.2% vs 36.%; P = .0053).
The ACC reviewers commented that MR-INFORM is an interesting study, stating, "The results of this trial indicate that MR perfusion–guided management of patients with stable angina is noninferior for the MACE endpoint at 1 year compared with invasive angiography and FFR. The overall event rate is fairly low with both strategies. This is the first trial to show that MR-perfusion imaging could guide patient management in a high risk population with the same effectiveness as invasive angiography with FFR."
However, they advised that there are a few caveats, which they outlined as follows, "First, it took a very long time to enroll this trial, and of more than 16,000 patients who were screened, less than 1,000 were finally randomized. This minimizes the generalizability of these results. Next, it is unclear if other functional imaging such as SPECT or dobutamine stress or even computed tomography-FFR would have provided similar results. For instance, patients with stable angina and class 2 symptoms are likely to undergo one of these tests in routine clinical practice before being referred for invasive angiography. The incremental utility of MR over other imaging modalities is thus unclear. The cost-effectiveness of this strategy also needs to be investigated."