Quantitative flow ratio (QFR) – a non-invasive fractional flow reserve (FFR) simulation using angiographic imaging – could “increase the practicability” of physiology-guided decision-making, the Japanese DECISION QFR study found. The findings were presented Tuesday at EuroPCR 2022 in Paris by Taku Asano, MD, PhD, from St. Luke's International Hospital, Tokyo. The functional SYNTAX score (FSS) was introduced in 2018 as a correction of the SYNTAX score (SS) – adding FFR to the solely anatomic measure. “Patient risk assessment considering coronary anatomy and its physiological significance, which is represented by the [FSS], demonstrated better capability in predicting the outcomes after revascularization in patients with multivessel disease [MVD] compared to one considering only anatomy,” said Asano. Yet, multivessel interrogations using FFR carry risk of vessel injury, as well as “excess procedure time” due to the associated pressure-wire manipulation, he said. QFR is an FFR simulation based on angiographic images “without using a pressure wire or pharmacological hyperemia,” Asano noted. The DECISION QFR study set out to investigate QFR’s potential in providing the physiological information required for an FSS in a heart team discussion in a bid to find an “optimal revascularization strategy for patients with MVD. It included 248 chronic coronary syndrome patients with two- or three-vessel disease (41.9% vs. 58.1%, respectively), including a proximal left anterior descending (LAD) coronary artery lesion, who were eligible for revascularization. The patients – recruited between August 2020 and October 2021 across 10 Japanese sites – had median anatomical SYNTAX scores of 20.9 ± 9.3, were a mean age of 70.8 years and included mostly male subjects (78.6%). The patients’ mean number of lesions with ≥ 50% stenosis was 3.9. The majority of patients (81%) had hypertension, dyslipidemia (77.8%), and/or three-vessel disease (58.1%), while 48.4% were diabetic. All of the patients had an LAD lesion, 79.4% had right coronary artery (RCA) lesions and 78.2% had left circumflex artery (LCX) lesions. The patients were randomized to receive heart team decisions based on either QFR or FFR and treatment with percutaneous coronary intervention (PCI) alone, coronary artery bypass graft surgery (CABG) alone or equipoise (CABG or PCI). Besides SS and FSS, SYNTAX score II 2020 based on FSS was utilized in heart team decisions, resulting in a mean 10-year post-PCI mortality estimate of 36.1% and a mean 10-year post-CABG mortality estimate of 29.6% at baseline. A total 483 vessels were analyzed by QFR and FFR. The level of agreement in treatment recommendations between the two groups as assessed by Cohen’s kappa – with treatments categorized as either “CABG only” or “equipoise/PCI only” – was set as the primary endpoint. Asano noted that the decision to categorize the three treatment groups into two categories was due to the current study being “inspired by the SYNTAX III trial, so in-line with that, to calculate the Cohen’s kappa, we need to make the components into two [groups].” This was met, with heart team discussions agreement in 91.5% of the cases, said Asano, with a Cohen’s kappa of 0.73 for the agreement of treatment recommendations endpoint (95% confidence interval [CI]: 0.62 – 0.83) – higher than the initial expectation of a 0.60 Cohen’s kappa score. The correlation coefficient between QFR and FFR was 0.68, and the area under the curve for a QFR predicting FFR – “positive or negative” – was 0.88, said Asano. The agreement of FSS based on QFR and FFR per interclass correlation coefficient (ICC) was 0.94, “which represented almost perfect agreement,” he added. Agreement of SYNTAX score terciles was 91.9%. Agreement of 10-year mortality estimates after PCI, based on SYNTAX score II 2020, was also “almost perfect” with an ICC of 0.998, Asano said. The secondary endpoint – vessel-level revascularization planning – agreement between the treatment strategies was observed “in more than 85% of the vessels,” resulting in the same Cohen’s kappa of 0.72 for both PCI and CABG (95% CI: 0.66-0.78). Additionally, QFR resulted in shorter procedure times compared to FFR of at 7.97 minutes per vessel vs. 8.38 minutes per vessel (P = 0.035). “QFR may enhance the practicability of physiology-guided decision-making for the optimal revascularization,” Asano concluded. ‘Good but not perfect,’ but still ‘primetime’ ready However, the study faced some questions from the panel members present during Asano’s presentation. Alexandra Lansky, MD, of the Yale School of Medicine, said the correlation between QFR and FFR of 0.68 is “good but not perfect,” adding that this, integrated into decision-making, leads to therapy agreement that is “actually very high, above 90%.” Giuseppe Di Gioia, MD, from Montevergine Clinic, Mercogliano, Italy, said, however, that QFR is “ready for primetime” usage across cath lab. “What this study adds to what we already know is that it is not necessary to have a one-to-one correlation with the FFR value – it is important that you have an agreement on whether to treat or not the patient.” Stéphane Fournier, MD, PhD, from the Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland, agreed, but stressed that “it’s really important to pay attention to the way we obtain images.” Although the current study had predefined projection angles for the QFR, “we realize that in our cath labs, if we perform some retrospective studies, it can be really more challenging”.