The impact of coronary microvascular dysfunction on the discordance between fractional flow reserve and resting full-cycle ratio in patients with chronic coronary syndromes

Jacek Legutko; Lukasz Niewiara; Bartlomiej Guzik; Piotr Szolc; Jakub Podolec; Marcin Nosal; Marta Diachyshyn; Krzysztof Zmudka; Paweł Kleczynski

doi:10.3389/fcvm.2022.1003067

The impact of coronary microvascular dysfunction on the discordance between fractional flow reserve and resting full-cycle ratio in patients with chronic coronary syndromes

Front Cardiovasc Med. 2022 Oct 5:9:1003067. doi: 10.3389/fcvm.2022.1003067. eCollection 2022.

Authors

Jacek Legutko^{1

2}, Lukasz Niewiara^{2

3}, Bartlomiej Guzik^{1

2}, Piotr Szolc^{1

2}, Jakub Podolec^{1

2}, Marcin Nosal⁴, Marta Diachyshyn², Krzysztof Zmudka^{1

2}, Paweł Kleczynski^{1

2}

Affiliations

¹ Department of Interventional Cardiology, Institute of Cardiology, Jagiellonian University Medical College, John Paul II Hospital, Krakow, Poland.
² Clinical Department of Interventional Cardiology, John Paul II Hospital, Krakow, Poland.
³ Department of Emergency Medicine, Faculty of Health Sciences, Jagiellonian University Medical College, Krakow, Poland.
⁴ Center of Invasive Cardiology, Angiology and Electrotherapy, Krosno, Poland.

Abstract

Background: Resting full-cycle ratio (RFR) is an alternative to fractional flow reserve (FFR) for the evaluation of borderline coronary artery lesions. Although FFR and RFR results are discordant in some cases, factors associated with the discordance remain unclear. The role of coronary microvascular dysfunction (CMD) is discussed as a potential mechanism to explain these discrepancies.

Aim: The study aimed to assess concordance between RFR and FFR in a real-life cohort from a high-volume center regarding the role of CMD.

Methods: Consecutive patients with borderline coronary lesions undergoing coronary functional testing for chronic coronary syndromes were included in the study. Measurements of RFR and FFR were performed alongside additional coronary flow reserve (CFR), resistance reserve ratio (RRR), and an index of microcirculatory resistance (IMR) measurements. CMD was defined according to the current guideline by either IMR ≥25 or CFR ≤2.0 in vessels with no significant stenosis.

Results: Measurements were performed in 157 coronary arteries, in 101 patients, with a median age of 66 y., 74% male, with prior history of arterial hypertension (96%), dyslipidaemia (91%), and diabetes (40%). The median value of vessel diameter stenosis was 45% according to QCA.Overall, FFR and RFR values were significantly correlated (r = 0.66, p < 0.001), where positive FFR/negative RFR and negative FFR/positive RFR were observed in 6 (3.8%) and 38 (24.2%) of 157 vessels. The RFR/FFR discrepancy was present in 44 (28%) of measurements. CMD was confirmed in 28 (64%) of vessels with discrepant RFR/FFR and in 46 (41%) of vessels with concordant results (p = 0.01). In discordant RFR/FFR vessels, as compared to concordant ones, significantly lower values of CFR [median 1.95 (IQR: 1.37, 2.30) vs. 2.10 (IQR: 1.50, 3.00), p = 0.030] and RRR [median 2.50 (IQR: 1.60, 3.10) vs. 2.90 IQR (1.90, 3.90), p = 0.048] were observed.Main predictors of RFR/FFR discrepancy in a univariate regression analysis were: higher age of patients [OR = 1.06 (1.01; 1.10), p = 0.010], presence of CMD [OR = 2.51 (1.23; 5.25), p = 0.012], lower CFR [OR = 1.64 (1.12; 2.56), p = 0.018], and lower RRR values [OR = 1.35 (95% CI: 1.03; 1.83), p = 0.038].

Conclusion: In discrepant RFR/FFR vessels, CMD is more prevalent than in concordant RFR/FFR measurements, which can be driven by lower CFR or RRR values. Further research is needed to confirm this observation.

Keywords: borderline lesions; chronic coronary syndromes; concordance; coronary artery disease; coronary microvascular dysfunction (CMD); fractional flow reserve (FFR); resting-full cycle ratio.