MR-INFORM: Myocardial Perfusion Based Strategy to Determine Need for Revascularization Shown to be Non-Inferior to Invasive Angiography in Reducing the Occurrence of Major Adverse Cardiovascular Events in Patients with Stable Angina

Fahad Alkhalfan, M.D.
By Fahad Alkhalfan, M.D. on

A trial led by Dr. Eike Nagel published in the New England Journal of Medicine showed that among patients with stable angina and risk factors for coronary artery disease, a myocardial-perfusion cardiovascular MRI based strategy to determine eligibility for revascularization was associated with a lower incidence of coronary revascularization than invasive angiography with fractional flow reserve (FFR) and was non-inferior to FFR in terms of the occurrence of major adverse cardiovascular outcomes.

The management of stable coronary artery disease consists of risk factor modification, medical therapy, and revascularization in patients with persistent symptoms despite conservative therapy. In patients who are symptomatic, there are two strategies that can help establish the diagnosis and guide treatment: (1) The use of invasive angiography to visualize the coronary arteries, followed by the measurement of the fractional flow reserve to guide the need for further treatment; (2) The use of non-invasive functional stress testing which if positive, is followed by invasive angiography and revascularization. However, the international guidelines are not consistent with respect to non-invasive testing. Myocardial perfusion cardiovascular magnetic resonance imaging (MRI) is a non-invasive test for the detection of coronary artery disease that typically leads to similar results when compared to FFR for the detection of ischemia. Currently, there is a lack of evidence with regards to whether an MRI based strategy to guide revascularization is comparable to an invasive angiography-based strategy. Finally, patients were assessed for the presence of symptoms at 12 months.

“In the MR-INFORM trial, we found that, in patients with stable angina and risk factors for coronary artery disease, the use of myocardial perfusion cardiovascular MRI in guiding initial management of patient care was non-inferior to the use of invasive coronary angiography combined with FFR with respect to the primary outcome of major adverse cardiac events at 1 year.” – Dr. Erik Nagel, M.D.

In the trial, patients 18 years or older with typical angina symptoms (Class 2 or 3 angina according to the Canadian Cardiovascular Society) and two or more cardiovascular risk factors (smoking, diabetes, hypertension, hyperlipidemia, or a family history of coronary heart disease) or a positive exercise treadmill test were randomized to either a MRI based strategy or FFR based strategy. Revascularization was recommended for patients in the MRI group with ischemia in at least 6% of the myocardium or in the FFR group with an FFR of 0.8 or less. The composite primary outcome was death, non-fatal myocardial infarction, or target vessel revascularization within 1 year. The investigators assessed non-inferiority. Additionally, the proportion of patients who met the criteria for revascularization as well as those who actually underwent randomization was assessed.

A total of 918 participants were randomized to either an MRI based strategy (454 participants) or an FFR based strategy (464 participants). Out of the patients in the study, 184 patients in the MRI group (40.5%) and 213 patients in the FFR group (45.9%) met the criteria for randomization (p= 0.11). Fewer patients in the MRI group actually underwent revascularization (162 (35.7%) vs 209 (45.0%), p = 0.005). The primary outcome occurred in 15 patients in the MRI group (3.6%) versus 16 patients (3.7%) in the FFR group (risk difference: −0.2%, 95% CI −2.7 to 2.4). The primary outcome met the non-inferiority criteria. Finally, the proportion of patients who were symptom-free at 12 months was similar between the two groups (49.2% in the MRI group vs 43.8% in the FFR group, p = 0.21).

The investigators found that in patients with stable angina and risk factors for coronary artery disease, a strategy involves first using myocardial perfusion cardiovascular in MRI to help guide the initial management of stable angina was non-inferior to using invasive angiography with regards to the composite efficacy outcome of death, non-fatal myocardial infarction, or target vessel revascularization by 1 year. Dr. Nagel highlighted some of the implications of this study and how it can help modify guidelines. He wrote, “Current guidelines on the management of the care of patients with suspected coronary artery disease separate diagnostic strategies from therapeutic strategies owing to a lack of evidence comparing combined diagnostic and therapeutic pathways.13 The MR-INFORM trial closes this knowledge gap by comparing two frequently used, well-defined, standardized, and validated9,14- 18 clinical management strategies. The cardiovascular-MRI methods used in this trial are readily available and can be implemented on standard MRI systems.” While the study does highlight a potential strategy for the management of patients with stable angina, it is important to note that patients were followed up for only 1 year.

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