Magnetic resonance perfusion or fractional flow reserve in coronary disease

Selected in The New England Journal of Medicine by P. Xaplanteris

The MR-INFORM study sought to compare the outcomes of a cardiovascular MRI-based strategy to an FFR-based strategy for guiding revascularisation in anginal patients.

References

Authors

Nagel E, Greenwood JP, McCann GP, Bettencourt N, Shah AM, Hussain ST, Perera D, Plein S, Bucciarelli-Ducci C, Paul M, Westwood MA, Marber M, Richter WS, Puntmann VO, Schwenke C, Schulz-Menger J, Das R, Wong J, Hausenloy DJ, Steen H, Berry C; MR-INFORM Investigators.

Reference

N Engl J Med. 2019 Jun 20;380(25):2418-2428

Published

June 2019

Link

Read the abstract

Reviewer

Panagiotis Xaplanteris

@panosxap

Interventional cardiologist / Cardiologist

Bruxelles, Belgium

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My Comment

Why this study – the rationale/objective?

The evaluation and subsequent treatment of patients with stable angina is frequently centred around invasive angiography and decisions for revascularisation are based on physiology metrics such as the fractional flow reserve (FFR). The MR-INFORM (Myocardial Perfusion CMR versus Angiography and FFR to Guide the Management of Patients with Stable Coronary Artery Disease) study sought to compare the outcomes of a cardiovascular MRI-based strategy to an FFR-based strategy for guiding revascularisation in anginal patients.

How was it executed – the methodology?

Using a non-inferiority design (risk difference of 6%), 918 patients were randomised to either the MRI-based or FFR-based group and the primary endpoint was a composite of death, myocardial infarction or target vessel revascularisation at 1 year.

Patients were referred for revascularisation if they had >=2 adjacent slices or a single transmural ischemic segment (approximately 6% of myocardial mass) or an FFR value of <=0.8.

What is the main result?

The average age was 62 years old, most patients were male (72%) with moderate ischemia (89% with CCS angina class II) and with a high pretest likelihood of coronary artery disease (CAD) (74%).

Fewer patients in the MRI-based group were revascularised compared to the FFR-guided group (35.7% versus 45%, P=0.005) and the primary endpoint did not differ between the two groups (3.6% versus 3.7%, 95% confidence interval -2.7 to 2.4), denoting that the new method was non-inferior to the comparator (FFR).

At 12 months, the percentage of patients that did not have angina was comparable between the two groups (49.2% versus 43.8%, P=0.21).

Critical reading and relevance for clinical practice

The MR-INFORM study is important for a number of reasons:

First, it solidifies the role of myocardial perfusion CMR as a first-line exam in the work-up of anginal patients. By doing so, and in the aftermath of the SCOT-HEART trial that evaluated the role of computed tomographic angiography (CTA) in a similar patient group, it widens the scope of non-invasive imaging by offering a non-ionising alternative. Taken together, these trials lend further support to the notion that imaging should act as a gatekeeper for patients with angina; only those with ischemia or relevant anatomic disease should be forwarded to the cathlab.

Second, the clinical outcomes of the two groups in the MR-INFORM study provide useful insights for stable CAD. More than half of the patients remain symptomatic at 12 months, highlighting the complex nature of the disease and alluding to a microvascular involvement. The non-blinded trial design, as well as the fact that medical therapy was not uptitrated to maximum tolerated doses prior to inclusion in the study should also be taken into account when interpreting these results.

Third, despite the fact that fewer patients were revascularised in the CMR group, the hard outcomes at 12-months did not differ. This finding takes what had been shown by the FAME studies one step further; fewer, but better-informed revascularisations (by physiology or myocardial perfusion CMR) result in similar outcomes.

Finally, it should be kept in mind that the availability of myocardial perfusion CMR is still limited. In addition, even in centres that have CMR at their disposal, it remains a modality for selected patients. This is reflected by the fact that only 5.5% of the originally assessed patients were enrolled in the trial.