The rate of major adverse cardiac events (MACE) over 5 years is similar whether revascularization is guided by instantaneous wave-free ratio (iFR) or fractional flow reserve (FFR), according to long-term results of the iFR-SWEDEHEART study.
“The results are about the same as reported at 12 months. There were no significant differences in any outcome we evaluated,” according to Matthias Götberg, MD, PhD.
When the initial results of the noninferiority iFR-SWEDEHEART trial wereafter 1 year of follow-up, the primary MACE endpoint of death from any-cause nonfatal myocardial infarction, or unplanned revascularization, was met by 6.7% and 6.1% of those randomized to iFR or FFR, respectively.
These outcomes were not significantly different and placed iFR well within the predefined boundaries of noninferiority (P = .007).
In this new and final follow-up of iFR-SWEDEHEART, which evaluated the same 2,019 patients who were alive at 1 year (none were lost to follow-up), the MACE endpoint was met by 21.5% and 19.9% of those managed with iFR and FFR, respectively. The hazard ratio (1.09) had a wide 95% confidence interval (0.90-1.31) that did not approach statistical significance.
No differences seen across outcomes
When broken down into the MACE components, there were no differences between iFR and FFR, respectively, for all-cause death (9.4% vs. 7.9%), MI (5.8% vs. 5.7%) or unplanned revascularization (11.6% vs. 11.3%).
Across predefined subgroups, such as those defined by age, gender, stable versus unstable angina, and presence of risk factors such as diabetes, hypertension, hyperlipidemia, and smoking, there were also no significant differences in outcome.
At the time iFR-SWEDEHART was initiated, FFR had already been accepted as more effective than angiographic assessment to identify lesion ischemia and the need for percutaneous intervention (PCI). The iFR-SWEDEHEART trial tested iFR, a relatively new technology at the time, as a noninferior alternative. Unlike FFR, which requires adenosine to dilate the vessel, adding cost and patient discomfort, iFR measures the resting pressure gradient across the coronary lesion, and it is generally easier to perform.
“The advantage of iFR is that it provides an instantaneous lesion assessment without the need for adenosine,” Dr. Götberg explained in presenting the results at the Transcatheter Cardiovascular Therapeutics annual meeting, held virtually and live in Orlando.
When the procedural results were compared in the published study at 1 year, it was noted that the mean number of lesions evaluated per patient was higher (1.55 vs. 1.43; P = .002), but the proportion of lesions found functionally significant was lower (29.2% vs. 36.8%; P < .0001) among those randomized to iFR than in the FFR group.
While most other procedural characteristics, such as PCI access route, fluoroscopy time, and contrast use did not differ significantly, fewer stents were placed in patients managed with iFR (1.58 vs. 1.73; P = .048), and a reduction in the average procedural time of a few minutes approached significance (P = .09).
Patient discomfort is greater with FFR
Patient discomfort measured during the procedure did differ, according to Dr. Götberg, an interventional cardiologist at Skåne University Hospital, Lund, Sweden.
Only about 30% in the FFR group reported no discomfort. Most of the others reported mild or moderate discomfort, but nearly 10% characterized the discomfort as severe. In the iFR group, more than 95% reported no discomfort. All of the remaining patients reported discomfort level as mild.
Because differences in MACE would be most likely to occur in the first year after revascularization, the similarity of the 1- and 5-year results were expected, according to Dr. Götberg. However, a 5-year follow-up was considered prudent given the relatively limited experience with iFR when the study was designed. This technique is now well established and widely used.
The study supports the premise that quicker and easier-to-obtain results with iFR are obtained without sacrificing greater relative risk of failing to identify a vulnerable lesion, according to Dr. Götberg.
Nevertheless, iFR and FFR “are not an exact match,” according to Jennifer A. Rymer, MD, an interventional cardiologist and assistant professor of medicine at Duke University, Durham, N.C. Although she called this trial an “excellent” demonstration of comparable utility in distinguishing lesions that do not require intervention from those that do, she implied that some clinicians might still prefer FFR for other reasons.
For example, FFR provides information about coronary flow reserve and microvascular resistance that are relevant to the underlying pathophysiology in a diseased vessel, according to Shmuel Banai, MD, head of interventional cardiology, Tel Aviv Medical Center. Recognizing that this information is not as readily generated by iFR, he is among those who plan to continue to use FFR despite these results.
However, for those who are now routinely performing iFR for the purposes of guiding revascularization, “these data are reassuring,” said David Kandzari, MD, director of interventional cardiology, Piedmont Hart Institute, Atlanta. The 5-year data essentially eliminate the likelihood that iFR relative to FFR increases the risk of missing functionally significant lesions for revascularization procedures.
Dr. Götberg reports financial relationships with Abbott, Boston Scientific, Medtronic, and Phillips Healthcare. Dr. Rymer reports no potential financial conflicts of interest. Dr. Banai has a financial relationship with Neovasc. Dr. Kandzari reports financial relationships with Ablative Solutions and Medtronic.