ST-elevation Myocardial Infarction (STEMI) patients with multi-vessel disease undergoing percutaneous coronary intervention (PCI) guided by fractional flow reserve (FFR) did not experience improved outcomes compared to angiography-guided procedures, according to the findings of the FLOWER-MI trial, presented during a late-breaking trial session at the American College of Cardiology’s 70th Annual Scientific Session (ACC.21, 15–17 May, virtual).
FLOWER-MI—FLOW Evaluation to Guide Revascularization in Multi-vessel ST-elevation Myocardial Infarction—involved a head-to-head comparison of outcomes in STEMI patients with multi-vessel disease who underwent either FFR-guided stenting or stenting guided by angiography alone.
FFR is performed during angiography to determine if the stenosis is significant and to guide the stenting procedure, Etienne Puymirat, professor of cardiology at the University of Paris, director of intensive care at the Georges Pompidou Hospital (Paris, France) and principal investigator of the study, explained. Previous studies have shown that STEMI patients treated with FFR-guided stenting had better outcomes than those treated with medication alone.
The trial, conducted at 41 centres in France, enrolled 1,171 patients who had a stent inserted into a blocked coronary artery after STEMI and who also had a second coronary artery that was at least 50% blocked. The patients’ average age was 62 years and 83% were men.
Immediately after their first stenting procedure, all patients were randomly assigned to undergo a second stenting procedure in the partially blocked artery, guided either by FFR or by angiography alone. The second procedure was performed within five days of the first during the same hospitalisation.
After 12 months, 5.5% of patients in the FFR-guided group had died, had another non-fatal heart attack or had undergone an additional stenting procedure, compared with 4.2% of those in the angiography-guided group, a non-statistically significant difference. Moreover, the FFR-guided procedure was more expensive than the one guided by angiography alone.
“The strategy of using FFR to guide the stenting procedure is not superior to the standard technique of using angiography to treat additional partially blocked arteries,” Puymirat told attendees at ACC.21. “In addition to having no benefit, we have also shown that, based on costs in France, the FFR-guided strategy is more expensive.”
The incidence of major adverse cardiovascular events in both groups of patients was considerably lower than the researchers expected, Puymirat said. “These patients were at high cardiovascular risk because of having multi-vessel disease,” he said. “Using data from previous trials and registries in this population, we estimated that about 15% of patients would have an adverse event within one year, but in our study the rate was 5% at one year.”
The study failed to meet its primary endpoint, a composite of death from any cause, non-fatal heart attack, or urgent need for an additional stenting procedure within 12 months. A secondary endpoint looking at cost-effectiveness favoured the use of angiography alone. However, the cost-effectiveness analysis was based on the costs of the two treatment approaches in France and might not be applicable in other countries, Puymirat said.