For patients with elevated ST myocardial infarction (STEMI) undergoing complete revascularization, percutaneous coronary intervention (PCI) guided by fractional flow reserve (FFR) in relation to PCI guided by angiography does not carry a significantly lower risk of death. or events, depending on the data. from the randomized FLOWER-MI trial.
Rather, 1-year events were numerically lower among those randomized to the angiography-guided approach, according to the trial’s lead researcher, Etienne Puymirat, MD, PhD.
Previous studies showing an advantage for FFR-guided PCI in patients with coronary syndromes provided the hypothesis that FFR-guided PCI would also be superior for guiding PCI in STEMI patients. At the multicentre Try FAME, for example, FFR-guided PCI for patients with multivessel disease was associated with fewer stent placements (Pg <.001) and an event rate almost 30% less than 1 year (Pg = 0.02).
While the advantage of complete revascularization, i.e., that PCI treatment of non-guilty and culpable injuries, has already been shown to be a better strategy than the treatment of culpable injuries alone, FLOWER-MI is the first large study comparing FFR with angiography to guide this approach in STEMI patients with multivessel disease, said Dr. Puymirat of the European Hospital George Pompidou, Paris, at the annual scientific sessions of the American College of Cardiology.
In this trial, which included several centers in France, patients with STEMI were eligible for randomization if they had a successful PCI from a culpable injury and 50% or more of stenosis in at least one additional injury with no intention of work. Complete revascularization, whether patients were randomized to angiography-guided PCI or FFR, was performed during index hospital admission. Patient management and follow-up were equally the same.
After a small number of exclusions, the populations intending to treat were 577 patients in the angiography-guided group and 586 in the FFR-guided group. The characteristics of the groups matched well with an average age of about 62 years and similar rates of risk factors, such as hypertension and diabetes.
Angiography equally good orientation
The main outcome was a compound of all-cause mortality, nonfatal MI, and unplanned revascularization. By proportion of risks, the risk of having one of these events within one year of PCI was numerically higher, with 32 in the FFR-guided group and 24 in the angiography group, but the difference was not statistically significant (1.32; Pg = .31).
However, the overall event rate was low (5.5% vs. 4.2% for the guided groups in angiography and FFR, respectively) and the confidence intervals were wide (95% CI: 0.78 -2.23). This was also true for the primary outcome components.
No sign of difference could be derived between strategies of these components, which included a higher rate of MI in the FFR-guided group (3.1% vs. 1.7%), but a lower mortality rate ( 1.5% vs. 1.7%).
Unplanned hospitalizations leading to revascularization rates were also low (1.9% and 2.6% for angiography-guided PCI and FFR, respectively), although the revascularization rate for nonprofit injury was approximately twice as high in the FFR group (53.3% vs. 27.3%).
At 1 year, there were also low rates and there were no significant differences in a list of secondary outcomes that included hospitalization for recurrent ischemia or heart failure, stent thrombosis, and revascularization. As within the primary composite outcome, no pattern could be seen in the secondary events, some of which were numerically more frequent in the FFR-guided group and some were lower.
In a cost-effectiveness analysis, the average cost per patient of the FFR-guided strategy was approximately 500 euros ($ 607) higher (8,832 vs. 8,322; Pg <.01), which led Dr. Puymirat to conclude that "the use of FFR for nonprofit injuries appears to be less effective but more expensive," at least because of the costs incurred in France.
Lack of interpretation of statistical power limits
FLOWER-MI’s conclusion is that FFR-guided PCI in complete revascularization of non-pacific lesions in STEMI patients is not superior to an angiography-guided approach, but Dr. Puymirat warned that the low number of events prevents a message. definitive.
William Fearon, MD, a professor of cardiovascular medicine at Stanford University Medical Center in California, agreed. Based on his calculations, the trial did not have enough power. Evaluating treatment details in the FFR group, Dr. Fearon noted that a risk-free injury was identified with an FFR of 0.80 or lower in approximately 55% of patients. Ultimately, 66% of the FFR group received PCI, eliminating the key distinction between strategies for most enrolled patients.
“Only about a third of FFR-guided patients, or about 200 patients, did not receive nonprofit PCI, and therefore only in this small group could we expect a difference in the results of the angio-guided group,” he said. Dr. Fearon.
In response, Dr. Puymirat acknowledged that the event rate of this trial, which was designed in 2015, was lower than expected. In recalculating the power required based on the rate of events observed in FLOWER-MI, it was estimated that about 8,000 patients would have been needed to show a significant difference in these PCI strategies.
Dr. Puymirat reports financial relationships with more than a dozen pharmaceutical companies, including Abbott, which provided some of the funding for this trial. Dr. Fearon reports financial relationships with Abbott, CathWorks, HeartFlow and Medtronic.
This article originally appeared on MDedge.com, which is part of the Medscape professional network.