August 08, 2018
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FFR-, iFR-based deferral of revascularization equally safe

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Deferral of revascularization based on instantaneous wave-free ratio and fractional flow reserve measurements results in similarly low rates of MACE, according to an analysis of two multicenter, randomized trials.

For this study, the researchers analyzed the pooled per-protocol population of 4,486 patients from the DEFINE-FLAIR and iFR-SWEDEHEART trials in which revascularization was deferred based on iFR or FFR. Patients were stratified according to clinical presentation and iFR- or FFR-guided decision-making.

At baseline, deferred patients in the iFR group vs. the FFR group were more likely to be men (72% vs. 68%; P = .05) and had higher Canadian Cardiovascular Society grading of angina pectoris (26.8% in class I and 32.8% in class II vs. 22.5% in class I and 27.9% in class II; P < .01 for the difference between groups).

Overall, fewer lesions were deferred in patients with ACS vs. stable angina (36% vs. 50%; P < .001). Furthermore, in patients with stable angina, more lesions were deferred with iFR vs. FFR (55% vs. 48%; P < .001), whereas deferral rates were similar with iFR and FFR in patients with ACS (36% vs. 36%; P = .91).

Comparable event rates

Among the 2,130 patients in whom coronary revascularization was deferred, deferral was more common in the iFR group than in the FFR group (50% vs. 45%; P < .01). Rates of MACE — all-cause death, nonfatal MI or unplanned revascularization — at 1 year were low and similar between the iFR and FFR groups (4.12% vs. 4.05%; fully adjusted HR = 1.13; 95% CI, 0.72-1.79).

The top contributor to the total MACE rates was unplanned revascularization at 1 year in both the iFR and FFR groups. The rates of unplanned revascularization, however, did not differ significantly (2.78% and 3.26%; P = .63) between the two groups. There were also no significant differences between the iFR and FFR groups in other individual components of the primary endpoint.

The researchers also found that the overall MACE rate was higher in patients with ACS vs. stable angina (7.7% vs. 6%; fully adjusted HR = 0.72 favoring stable angina; 95% CI, 0.55-0.93), which was primarily driven by the 1-year MACE rate among deferred patients with ACS vs. stable angina (5.9% vs. 3.6%; fully adjusted HR = 0.61 favoring stable angina; 95% CI, 0.38-0.99).

Additionally, in the deferred group, clinical presentation influenced the MACE rate more in patients evaluated with FFR (unadjusted HR = 0.52 favoring stable angina; 95% CI, 0.27-1) vs. iFR (unadjusted HR = 0.74; 95% CI, 0.38-1.43). However, this interaction was not statistically significant.

‘Equally valid’

In light of these findings, Fernando Alfonso, MD, PhD, and Fernando Rivero, MD, both from the Hospital Universitario de La Princesa in Madrid, highlighted several issues with the study in an accompanying editorial.

For instance, they noted that it would be interesting to know more about the unplanned revascularizations, including whether they were performed at the initially deferred lesion, whether lesion severity had remained unchanged or progressed and whether the deferred lesions had physiological results close to the threshold for intervention. They also discussed other considerations, such as a lack of information on anti-anginal medications and the potential for a placebo effect in deferred lesions that may have prevented repeat angiography and revascularization.

“All the aforementioned considerations do not undermine the value of this well-designed study from the largest dataset available on coronary physiology but rather indicate that future research is warranted to get further insights on the relative value of these different physiological indexes,” Alfonso and Rivero wrote.

“Results of the present study clearly demonstrate that among patients with coronary artery disease and intermediate coronary stenosis, both FFR and iFR are equally valid to defer coronary revascularization,” Alfonso and Rivero wrote. – by Melissa Foster

Disclosures: DEFINE-FLAIR and iFR-SWEDEHEART were funded by Philips (formerly Volcano). Escaned reports he is a speaker and consultant for Abbott, Boston Scientific and Philips, and received personal fees from Abbott/St. Jude Medical, Boston Scientific and Philips Volcano outside the submitted work. Please see the study for all other authors’ relevant financial disclosures. Alfonso and Rivero report no relevant financial disclosures.