Dr. Ömer Furkan Demir

Name of the study: Quantitative flow ratio versus fractional flow reserve for coronary revascularisation guidance (FAVOR III Europe): a multicentre, randomised, non-inferiority trial

Published in congress: TCT 2024

Link:   https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(24)02175-5/abstract

Introduction:
Fractional flow reserve (FFR) or non-hyperemic pressure ratios are recommended to assess the functional significance of intermediate coronary lesions. These methods require the placement of a pressure wire in the coronary artery during invasive coronary angiography. Quantitative flow ratio (QFR) is an angiography-based calculation method for estimating FFR that does not require the use of pressure wires and does not require hyperemic drugs.

Objective:
This study aimed to compare the clinical results of the QFR-based diagnostic strategy with the FFR-based strategy at 12-month follow-up.

Methods:
FAVOR III Europe is a multicenter, randomized, open-label study comparing QFR-based and FFR-based diagnostic strategies for patients with moderate coronary stenosis. Thirty-four centers from 11 European countries were included in the study. Patients aged 18 years and older with a diagnosis of chronic coronary syndrome or stable acute coronary syndrome and at least one moderate non-culprit stenosis (visually 40–90% stenosis; defined here as a study-eligible lesion) were randomly assigned (1:1) to QFR or FFR groups. A value of ?0.80 in QFR and FFR measurements was considered an indication for coronary revascularization. Exclusion criteria were: STEMI within the last 24 hours, cardiogenic shock, GFR <20 ml/min/1.73 m2, LVEF <30%, atrial fibrillation, and allergy to contrast and adenosine. The primary endpoint was the composite of death, myocardial infarction, and unplanned revascularization at 12 months.

Results:
2000 patients were enrolled in the study between 2018 and 2023 and randomly assigned to QFR-guided strategy (1008 patients) or FFR-guided strategy (992 patients). The mean age of the patients in the study was 67.3 years, and 462 patients (23.1%) were female. The mean follow-up of the patients was 365 days. At 12 months, 67 (6.7%) patients in the QFR group and 41 (4.2%) patients in the FFR group had a primary endpoint event (hazard ratio 1.63 [95% CI 1.11-2.41]). QFR did not meet the non-inferiority target over FFR. A total of 18 (1.8%) patients in each group experienced an adverse procedure-related event; the most common of these was procedure-related myocardial infarction, which occurred in ten (1.0%) patients in the QFR group and seven (0.7%) patients in the FFR group. One patient in the QFR group died related to the index procedure.

Conclusions:
The results of the FAVOR III European study do not support the use of QFR when FFR is available to guide revascularization decisions in patients with moderate coronary stenosis.

Comment:
Quantitative flow rate (QFR) is not as effective as fractional flow rate (FFR) as a guide to revascularization in patients with intermittent coronary stenosis in terms of 12-month clinical outcomes, according to FAVOR III Europe. According to Birgitte Krogsgaard Andersen, MD, these findings call into question current guidelines for functional assessment. QFR was given a class I, level of evidence B indication in the 2024 European Society of Cardiology (ESC) guidelines for chronic coronary syndromes.
QFR is a wireless, angiography-based approach that uses computer software to estimate FFR, whereas traditional FFR uses a pressure wire under adenosine-induced hyperemia to measure coronary flow. Without the need for a wire or adenosine, QFR has the potential to reduce risks, side effects, and costs for patients. However, the results obtained show that despite this ease of use, QFR does not provide as accurate results as FFR. The reasons for this are thought to be interobserver variability and software differences.