Stress Perfusion Imaging Non-Inferior for Patients with Stable Coronary Artery Disease

Magnetic resonance (MR) perfusion guided management of patients with stable angina is non-inferior to invasive angiography and fractional flow reserve (FFR), meeting its primary endpoint.

For the MR-INFORM trial, the investigators sought to assess the safety and efficacy of MR-based perfusion imaging compared with invasive angiography and FFR among patients with stable angina on optimal medical therapy (OMT).

Patients were randomized to receive either invasive angiography plus FFR or MR perfusion imaging. In the FFR arm, invasive angiography was performed in all patients.

FFR was recommended in arteries >2.5 mm with a stenosis of 40% to 90%. If FFR <0.8, revascularization (percutaneous coronary intervention [PCI] or coronary artery bypass grafting [CABG]) was recommended.

For patients receiving an MR perfusion, it was performed with a 1.5 T scanner using cine imaging. If transmural defect or subendocardial defect >2 segments or 2 adjacent slices were found, angiography with the goal of revascularization was recommended. All the patients received OMT.

Overall, 16,620 patients were screened for the study with 918 patients enrolled. The mean age was 62 years, with 28% of participants’ female. The duration of follow-up was 1 year.

The primary endpoint was major adverse cardiac events (MACE) at 1 year. FFR patients were 3.9% compared with 3.3% who received MR. Death was 0.22% for FFR versus 0.89% MR; myocardial infarction: 1.7% versus 1.8%; and repeat revascularization was 1.9% versus 0.7%, respectively.

Secondary outcomes for FFR versus MR were: negative angiography in 35.6% of FFR patients versus 8.1% of MR patients, of which only 49.6% of MR patients needed invasive angiography. Figures for revascularization during index event were 44.2% versus 36%, respectively.

The findings indicated that MR-perfusion guided management of patients with stable angina is non-inferior for the MACE endpoint at 1 year compared with invasive angiography and FFR. Additionally, the overall event rate was relatively low with both approaches.

“This is an interesting study, but there are a few caveats,” the authors wrote. “First it took a very long time to enroll in this trial, and of >16,000 patients who were screened, <1000 were finally randomized. This minimized the generalizability of these results. Next, it is unclear if other functional imaging such as SPECT or dobutamine stress or even CT-FFR would have provided similar results.

For instance, patients with stable angina and class II symptoms are likely to undergo 1 of these tests in routine clinical practice before being referred for invasive angiography. The incremental utility of MR is thus unclear. The cost-effectiveness of this strategy also needs to be investigated.

The findings were presented at the American College of Cardiology Annual Scientific Session in Washington, DC.