Mid-term data continue to show non-inferiority of resting instantaneous wave-free ratio (iFR) when tested against hyperaemic fractional flow reserve (FFR), said Javier Escaned (Hospital Clinico San Carlos, Madrid, Spain) who reported a pooled, nearly 4,500 patient-level analysis of DEFINE FLAIR and iFR SWEDEHEART trials during the PCR e-Course 2020.
Escaned told course participants: “Revascularisation deferral, which is the decision to treat medically, is a key aspect of physiology-based coronary revascularisation. In the post-ISCHEMIA trial scenario, it is key to understand whether decision-making with hyperaemic- and non-hyperaemic indices lead to similar rates of revascularisation, and if this happens over the shifting age range of coronary patients”.
Speaking in a late-breaking trials session, Escaned explained that since the results of pivotal studies from the late 1990s, the demographics of patients undergoing pressure guidewire studies have changed significantly. “The age range of patients in the cath lab has expanded significantly since the pivotal DEFER trial 20 years ago. Understanding whether FFR or iFR-based deferral of revascularisation is equally safe in younger and older individuals is important,” he stated.
The researchers undertook a pooled patient-level analysis of two randomised trials investigating the safety of iFR: DEFINE FLAIR, which included 2,467 patients and iFR-SWEDEHEART, which included 2,019 patients. They investigated whether the two-year outcomes of deferred revascularisation are similar when the decision is based on FFR or iFR; they also examined the relationship between patient age, revascularisation decision based on FFR or iFR, and clinical outcomes. The primary endpoint was major cardiac events (MACE), defined as a composite of death, non-fatal myocardial infarction and unplanned revascularisation, at two years.
Two-year follow-up analyses showed that deferral of coronary revascularisation, based on either of the indices, were equally safe. PCR e-Course attendees heard that the MACE rate in deferred patients (n=2,130) was virtually identical in the iFR (7.43%) and FFR arms (7.40), without significant differences in death, myocardial infarction and revascularisation rates.
A press release from PCR noted that overall (n=4,486), FFR led to 5% more interventions than iFR and that in patients under 60 years of age, this effect was more marked with FFR leading to 12% more revascularisation procedures than iFR (deferral with iFR 54%; with FFR 42%; p<0.01).
“Of note, age influenced two-year MACE in a remarkable manner only in patients with FFR-based deferral (FFR deferred HR 1.95 [95% CI 1.03, 3.70]; FFR treated HR 0.96 [0.67, 1.37]; p=0.06). This interaction with age was not observed in patients deferred or treated based on iFR values,”
In the final slide of his presentation, Escaned shared data from recent research (JACC Cardiovasc Interv. 2020 Jan 13;13(1):20-29.) demonstrating that hyperaemic coronary flow (used for FFR calculation) decreases over age, while resting flow (used by iFR) remains unaffected. “This may explain why we see age-related differences in PCI deferral when FFR or iFR are used in decision-making”, he added.
Farrel Hellig (Johannesburg, South Africa) led the ensuing discussion.