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Stress MRI or FFR in Coronary Disease
Study Questions:
In patients with typical angina, does stress magnetic resonance imaging (MRI) or fractional flow reserve (FFR)-based management lead to better outcomes?
Methods:
Investigators conducted a two-arm randomized multicenter trial of patients with typical angina and Canadian Cardiovascular Society (CCS) class II or III symptoms and either 2 or more cardiovascular risk factors or positive exercise treadmill test. Patients were randomized to either stress cardiac MRI- or FFR-guided management. They were followed for a primary composite outcome of death, nonfatal myocardial infarction, or target vessel revascularization at 12 months. The study was designed to demonstrate noninferiority of the MRI-guided strategy with a noninferiority margin of 6%, meaning the upper confidence interval of the event rate in the MRI-guided arm was no higher than 6 percentage points more than in the FFR-guided arm.
Results:
A total of 918 patients were enrolled out of 16,620 screened. The most common reason for exclusion was CCS class I angina (n = 6,717); 49% of those assigned to MRI had a positive test for ischemia. Likewise, 61% (n = 282) of those assigned to FFR had abnormal angiography and of those, 213 (45%) had abnormal FFR. Consequently, similar numbers of abnormal FFR and CMR were similar. However, the number of patients who underwent initial revascularization was lower in the CMR group than the FFR group (162 [35.7%] vs. 209 [45.0%], p = 0.005). After a median follow-up of 375 days, lipids and blood pressure improved in both arms (~15 mmol/L decrease in low-density lipoprotein and ~10 mm Hg decrease in systolic blood pressure). The primary outcome occurred in 15 (3.6%) patients assigned to MRI and 16 (3.7%) of those assigned to FFR (difference of 0.2%; 95% confidence interval, -2.7 to 2.4).
Conclusions:
In patients with typical angina, a stress CMR-guided strategy is noninferior to an FFR-guided strategy.
Perspective:
This is an important study, which demonstrates that it is reasonable to use stress CMR in the management of patients with stable angina. A few specific conclusions are notable. First, in this cohort, the prevalence of ischemia was approximately one in two. This is markedly higher than in many stress testing cohorts and may reflect the inclusion criteria requirement of typical angina and CCS II/III symptoms. Perhaps as a consequence, the proportion of men in the study was much higher than women (72% male). Nonetheless, this study underscores that evaluation of high pretest probability patients will lead to a high positive predictive value, as seen in this study.
Second, the use of optimal medical therapy during the study was excellent, with notable improvements in lipid and blood pressure control, underscoring the central importance of medical therapy in stable patients with angina.
Third, in this study (as in FAME and FAME2 trials), the arm with fewer revascularizations did equivalent or better with respect to major adverse cardiac events, raising doubt about the prognostic benefit of revascularization. Nonetheless, nearly all patients who underwent revascularization had documentation of ischemia via CMR or FFR, so this study cannot evaluate the hypothesis that ischemia-guided revascularization is superior to medical therapy alone.
Nonetheless, this study should be practice changing and shows that stress CMR and FFR are equivalent for management of patients with stable angina. It also may have implications for the management of angina patients more broadly, and in particular, those with discordant noninvasive and invasive measures of ischemia.
Clinical Topics: Cardiac Surgery, Cardiovascular Care Team, Dyslipidemia, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Prevention, Stable Ischemic Heart Disease, Atherosclerotic Disease (CAD/PAD), Cardiac Surgery and Arrhythmias, Cardiac Surgery and SIHD, Lipid Metabolism, Interventions and Coronary Artery Disease, Interventions and Imaging, Angiography, Magnetic Resonance Imaging, Nuclear Imaging, Chronic Angina
Keywords: Angina, Stable, Angiography, Blood Pressure, Coronary Artery Disease, Diagnostic Imaging, Exercise Test, Fractional Flow Reserve, Myocardial, Lipids, Lipoproteins, LDL, Magnetic Resonance Imaging, Magnetic Resonance Spectroscopy, Myocardial Infarction, Myocardial Ischemia, Myocardial Revascularization, Primary Prevention, Risk Factors
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