A pooled patient-level analysis of patients undergoing physiological assessment, with either fractional flow reserve (FFR) or instantaneous wave-free ratio (iFR), indicates that deferring coronary interventions in contemporary clinical practice is safe—particularly in stable patients. However, a small but significantly higher risk of major adverse cardiac events (MACE) at one year was found when revascularisation deferral was performed in patients with acute coronary syndrome.
Study investigator Javier Escaned (Hospital Clinico San Carlos IDISSC / Complutense University, Madrid, Spain) reported the study suggested that this difference in outcomes relates to suboptimal decision in the context of acute coronary syndrome, rather than the higher patient risk profile. Presenting the data at EuroPCR (16–19 May, Paris, France), he added that a “key benefit” of physiological assessment was to “avoid unnecessary coronary interventions” by deferring percutaneous coronary intervention (PCI) in non-significant stenoses. Deferral is a major driver of the documented improvement in patient outcomes and cost-efficiency of pressure guidewire- based revascularisation.
He noted that, until now, the safety of deferring PCI in patients with stable coronary artery disease on the grounds of FFR was supported by the DEFER trial, performed 17 years ago. Yet, he observed, “major changes in PCI and pharmacological treatment that might affect outcomes” have taken place in the years since the study (DEFER). Furthermore, pressure guidewires are currently used not only in stable angina patients, but also in those presenting with acute coronary syndromes. Escaned said that in this important patient subset, recent studies had “cast doubt” on the safety of deferring stenting in non-culprit lesions. “Given the growing proportion of patients presenting with acute coronary syndrome, establishing whether deferral of PCI is as safe as in stable angina is an urgent matter,” he added.
To address these issues, using a pooled patient-level analysis of the DEFINE FLAIR and iFR SWEDEHEART (which both indicated that iFR was non-inferior to FFR in terms of MACE at year), Escaned and colleagues evaluated the safety of deferring stenting, using contemporary techniques, in both stable and acute patients. The study aimed also to compare the safety of revascularisation deferral based on iFR, compared with FFR.
Stenting was deferred in 2,130 of the overall patient population (4,529). Of these, 1,675 had stable disease (of whom, 885 had been randomised to iFR and 790 had been randomised to FFR in the original studies) and 440 had acute coronary syndromes (of whom, 222 had been randomised to iFR and 218 had been randomised to 218).
Overall, the MACE rate in the deferred population at one year was—Escaned said—“very low”. The rate of MACE at one year in the stable disease group was 3.6%. “There was an extremely low event rate in stable coronary artery disease patients,” Escaned commented. He added: “This is very good news as it means that, compared with the DEFER trial, we have dramatically improved the safety of deferring stenting.” There were no significant differences between those assigned to iFR and those assigned to FFR; an important fact, since iFR-based interrogation was associated with less PCI procedures (i.e. more PCI deferral) than FFR.
However, compared with the stable group, the rate of MACE at one year in patients presenting with acute coronary syndromes was significantly higher (5.9%). While this excess risk may relate to the higher risk profile of patients with acute coronary syndrome, Escaned observed, there were no significant differences in the one-year rate of MACE between acute and stable patients in the treated population. He stated: “In treated patients, clinical presentation did not influence the rate of MACE. This raises the hypothesis that the excess of risk in deferred patients with acute coronary syndrome comes from suboptimal decision making based on physiological assessment.” Further research might focus on whether transient changes in the coronary circulation during the acute phase of the syndrome may affect the reliability of pressure-derived measurements of stenosis severity.
Concluding, Escaned noted: “Deferring of myocardial revascularisation, based on pressure interrogation, was more frequently performed when iFR was used compared to FFR, was associated with low and similar one-year outcomes in the FFR and iFR guided arms, and was associated with higher MACE rates in patients presented with acute coronary syndrome than with stable coronary artery disease.”