Virtual Flow Reserve (VFR): Virtual Physiological Test with OCT

Assessing intermediate coronary lesions with intracoronary physiology tests such as fractional flow reserve (FFR) or other non-hyperemic indices is considered the standard of care by both American and European societies. Likewise, intravascular imaging techniques (IVI), be it IVUS or optical coherence tomography (OCT), are of great use in assessing and guiding complex coronary lesions and are also recommended by the current guidelines. 

Virtual Flow Reserve (VFR): prueba fisiológica virtual con OCT

We are aware that the concomitant use of these techniques might be of greater diagnostic value; however, they are rarely used together, mainly because of cost concerns. 

Thanks to the recent development of specific software, we can now combine the diagnostic power of an IVI derived physiological perspective and simultaneous planning using FFR simulation models. 

The aim of this study was to validate the diagnostic performance of virtual flow reserve (VFR) in intermediate lesions vs. FFR. 

FUSION is a multicenter, prospective, single arm study carried out in 27 centers across the US. VFR was mathematically derived from a parameter flow model based on 3-dimensional coronary lumen morphology defining vessels as a flow limiting resistance network. Patients requiring predilation for OCT guidewire crossing, and culprit vessels in acute coronary syndromes (ACS) were excluded.

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Co-primary outcomes included sensitivity and specificity in VFR vs. FFR as standard. Vessels were assessed using Dragonfly OPTIS OCT and PressureWire X for FFR.

The primary analysis included 266 vessel assessments with OCT and FFR from a total 312 patients in 27 centers. Mean patient age was 67.4 ± 9.2, 30.4% were women and 36.5% were diabetic. Most patients presented stable (47.3%) or unstable angina (37.9%). Mean angiographic diameter stenosis was 65.5 ± 14.9%, with mean length 19.4 ± 9.3 mm.

Mean FFR resulted 0.83 ± 0.11, with positive FFR in 38.4% of the population, (≤0.80). Mean VFR was 0.81 ± 0.12, and 41.4% presented pathological value (≤0.80). Accuracy resulted 82%, sensitivity 80.4%, and specificity 82.9%, with 74.5% positive predicting value (PPV) and 87.2% negative predicting value (NPV) when looking at VFR vs. a FFR. The area under the curve for diagnosis was 0.88.

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The proposed treatment according to angiographic results was 37.1% for optimal medical treatment (OMT), 62.1% for PCI and 0.4% for CABG. Decision making with OCT, resulted in 32.1% OMT, and 65.2% PCI, while FFR assessment saw higher OMT (45.5% (p=0.005)) and lower PCI (52.2% (p=0.007)) rates. Compared against OCT, conventional PCI resulted in a reduction in correct stent diameter by 49% vs. 83.6% according to OCT.


The FUSION study represents the largest prospective study on physiology derived OCT vs invasive FFR, and shows VFR is technically feasible and offers great diagnostic accuracy. The adequate use of VFR has led to changes in clinical decision making. 

Dr. Omar Tupayachi

Dr. Omar Tupayachi.
Member of the Editorial Board of

Original Title: Optical Coherence Tomography–Based Functional Stenosis Assessment FUSION-A prospective Multicenter Trial.

Reference: Jeremias A, Maehara A, Matsumura M, Shlofmitz RA, Maksoud A, Akasaka T, Bezerra HG, Fearon WF, Samady H, Samuels B, Rapkin J, Gopinath A, Teraphongphom NT, Buccola J, Ali ZA. Optical Coherence Tomography-Based Functional Stenosis Assessment: FUSION-A Prospective Multicenter Trial. Circ Cardiovasc Interv. 2024 Mar 25:e013702. doi: 10.1161/CIRCINTERVENTIONS.123.013702. Epub ahead of print. PMID: 38525609.

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