Presented by Dr. Etienne Puymirat at the American College of Cardiology Virtual Annual Scientific Session (ACC 2021), May 16, 2021 the FLOWER-MI Study of Multivessel PCI Guided by FFR or Angiography for Myocardial Infarction. [N Engl J Med 2021;May 15:[Epub ahead of print] attempted to determine whether the use of FFR in addition to angiography in STEMI patients would improve cardiovascular outcomes, compared to the standard angiographically guided PCI, by assessing the relevance of non-culprit lesions. A secondary objective assessed the safety and the cost-effectiveness of the FFR-guided strategy compared to the angiography-guided strategy.
There were 1,171 patients who underwent primary PCI for STEMI and had nonculprit multivessel coronary disease, who were randomized to FFR-guided revascularization (n = 590) versus angiography-guided revascularization (n = 581) and followed for 12 months. The primary outcome of death, MI, or urgent revascularization occurred in 5.5% of the FFR-guided group compared with 4.2% of the angiography-guided group (p = 0.31). There was no difference in non-fatal MI (3.1 vs 1.7%, p=ns) or urgent revascularization (2.6 vs 1.9%, p=ns) between strategies. One can interpret the results to mean among patients who underwent primary PCI for STEMI and had nonculprit multivessel coronary disease, FFR-guided revascularization was not superior to angiography-guided revascularization.
While some advocates of physiologically guided ACS interventions will be disappointed, after speaking with Dr. Nils Johnson, I agree that one message is that FFR identify 1/3 of non-culprit lesions that can safely be deferred without MACE. A high FFR supports deferring unnecessary interventions, findings repeatedly produced in FAME, FAME, DEFER and other similar studies over the last two decades. As in FAME I, there is potential cost saving in FLOWER-MI applying FFR to defer stenting in the nonculprit vessel.
One limitation on all studies comparing two interventional strategies with different indications (for example, iFR versus FFR in Swedeheart iFR or Define Flair) such as angiographic severity versus FFR in the Flower MI study, is the inclusion of lesions that are angio+/FFR+ and thus receive the same treatment in both arms. Lesions with FFR<0.8 ( about 50% of subjects) will be treated by PCI in both arms and thus dilute out any differences between the two groups.
The details of FLOWER MI also add to some reticence on my part to accept the strength of the conclusions. For example, there were more non-culprit lesions in the FFR-guided group: 980 vs 891 (p=0.031) suggesting that operators were interested in FFR more than PCI. In such comparative trials, the lesions planned for intervention should be recorded in advance of randomization thus leveling the field as was done in FAME. FFR resulted in a significant reduction in revascularization, with the FFR-guided strategy reducing non-culprit PCI by almost 40% compared to an angio-based strategy.
While an overall negative trial for FFR related reductions in MACE, the use of physiology in the nonculprit lesions in STEMI patients, I believe has significant clinical and economic value, something likely demonstrated in future trials.
a, MSCAI, FAHA, FACC is chief of cardiology at VA Long Beach Health Care System, and Professor of Medicine at University of California, Irvine.
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