Summary of the Original Article
The aim of the present study was to demonstrate whether a cardiovascular MRI–based strategy was non-inferior to an FFR based strategy with respect to major adverse cardiac events in patients with typical angina and either two or more cardiovascular risk factors or a positive exercise treadmill test. The authors performed an unblinded, multicenter trial by randomly assigning 918 patients to a cardiovascular MRI–based strategy or an FFR-based strategy. Revascularization was recommended for patients in the cardiovascular-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, nonfatal myocardial infarction, or target-vessel revascularization within 1 year. The non-inferiority margin was a risk difference of 6 percentage points. A total of 184 of 454 patients (40.5%) in the cardiovascular-MRI group and 213 of 464 patients (45.9%) in the FFR group met criteria to recommend revascularization (P = 0.11). Fewer patients in the cardiovascular-MRI group than in the FFR group underwent index revascularization (162 [35.7%] vs. 209 [45.0%], P = 0.005). The primary outcome occurred in 15 of 421 patients (3.6%) in the cardiovascular-MRI group and 16 of 430 patients (3.7%) in the FFR group (risk difference, −0.2 percentage points; 95% confidence interval, −2.7 to 2.4), findings that met the noninferiority threshold. The percentage of patients free from angina at 12 months did not differ significantly between the two groups (49.2% in the cardiovascular-MRI group and 43.8% in the FFR group, P = 0.21).
Comments to the Article
This is a relevant clinical trial investigating two different diagnostic strategies in order to optimize the management of patients with typical angina and either two or more cardiovascular risk factors or a positive exercise treadmill test. The study was well conducted. The use of cardiovascular MRI dramatically reduced the number of coronary angiograms (48.2% vs 96.8% in FFR group), with subsequent less revascularizations in MRI group (35.7% vs 40.5%, p = 0.005). Unfortunately the authors missed a cost analysis, that would have certainly played in favour of the MRI-guided strategy. The two strategies were clinically equivalent in terms of primary endpoint (3.6% vs 3.7%). The non-inferiority of cardiovascular MRI guided vs FFR guided strategy was met, with a similar percentage of angina-free patients was observed in both groups at 1 year follow-up. It must be remarked that the authors compared two diagnostic rather than two therapeutic strategies. In fact, medical therapy was not maximized before randomization neither the authors investigated (by a special arm) the potential benefits of a conservative as compared to invasive strategy. Furthermore, no technical information was provided on percutaneous or surgical revascularization. Finally, a major limitation, well recognized by the authors, is that the expected event rate was much higher than the one finally observed (10% vs 3.7%), with a very large non inferiority margin (6%), much higher (almost double) than the final event rate. Therefore, future large and well powered trials with long-term follow-up are certainly needed in order to investigate these two strategies after maximization of medical therapy, especially in light of the results of the ISCHEMIA trial, and with a special regard to ACS patients with residual coronary disease after treatment of the culprit vessel.