In the next days, Dr. Seung Hun and colleagues will publish in J Am Coll Cardiol Intv 2019 a study that answers the title question and also brings peace of mind about the decisions we make based on one of these measurements or the other.

This study assessed the physiologic characteristics of discordant lesions between instantaneous wave-free ratio (iFR) and fractional flow reserve (FFR), and their impact on the prognosis at 5 years.

Both iFR and FFR are standard methods for the assessment of the functional significance of coronary artery lesions. However, there is a lack of literature regarding how to manage cases in which the results for these measurements do not match, and regarding the clinical impact of making decisions based on one method over the other.

Researchers evaluated a total of 840 vessels from 596 patients classified in groups according to iFR and FFR: high iFR–high FFR (n = 580), low iFR–high FFR (n = 40), high iFR–low FFR (n = 69), and low iFR–low FFR (n = 128). These patients were compared with a control group.

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Differences were measured and observed through other methods, such as coronary flow reserve (CFR), index of microcirculatory resistance (IMR), and resistance reserve ratio (RRR), reflecting the vasodilatory capacity of coronary microcirculation.

The follow-up period was 5 years, and researchers registered all-cause death, any infarction, and any revascularization, comparing revascularized patients with those who were deferred.

In the low iFR–high FFR group, all other measurements (CFR, RRR, and IMR) were similar to those of the low iFR–low FFR group. In the high iFR–low FFR group, the other parameters were similar to those of the control group.

Among the 4 groups, when classified by iFR and FFR, CFR and RRR are significantly different, unlike IMR.

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Such discordance between iFR and FFR did not affect the clinical endpoints.

Significant differences in the endpoints were present only upon comparison between the low iFR–low FFR and the high iFR–high FFR groups (p = 0.018).

Conclusion

There were differences in coronary function, especially in the vasodilatory capacity, between patients with iFR and FFR discordance. However, such discordance did not impact clinical results at 5 years.

Original title: Physiologic Characteristics and Clinical Outcomes of Patients With Discordance Between FFR and iFR.

Reference: Seung Hun Lee et al. J Am Coll Cardiol Intv 2019, article in press.

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