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Background: Myocardial ischaemia results from insufficient coronary blood flow. Computed virtual fractional flow reserve (vFFR) allows quantification of proportional flow loss without the need for invasive pressure-wire testing. In the current study, we describe a novel, conductivity model of side branch flow, referred to as 'leak'. This leak model is a function of taper and local pressure, the latter of which may change radically when focal disease is present. This builds upon previous techniques, which either ignore side branch flow, or rely purely on anatomical factors. This study aimed to describe a new, conductivity model of side branch flow and compare this with established anatomical models., Methods and Results: The novel technique was used to quantify vFFR, distal absolute flow (Qd) and microvascular resistance (CMVR) in 325 idealised 1D models of coronary arteries, modelled from invasive clinical data. Outputs were compared to an established anatomical model of flow. The conductivity model correlated and agreed with the reference model for vFFR (r = 0.895, p < 0.0001; ＋0.02, 95% CI 0.00 to ＋ 0.22), Qd (r = 0.959, p < 0.0001; -5.2 mL/min, 95% CI -52.2 to ＋13.0) and CMVR (r = 0.624, p < 0.0001; ＋50 Woods Units, 95% CI -325 to ＋2549)., Conclusion: Agreement between the two techniques was closest for vFFR, with greater proportional differences seen for Qd and CMVR. The conductivity function assumes vessel taper was optimised for the healthy state and that CMVR was not affected by local disease. The latter may be addressed with further refinement of the technique or inferred from complementary image data. The conductivity technique may represent a refinement of current techniques for modelling coronary side-branch flow. Further work is needed to validate the technique against invasive clinical data., Competing Interests: Declaration of competing interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. This independent research was carried out at the National Institute for Health and Care Research (NIHR) Sheffield Biomedical Research Centre (BRC). The views expressed are those of the author(s) and not necessarily those of the NIHR or the Department of Health and Social Care., (Crown Copyright © 2024. Published by Elsevier Ltd. All rights reserved.)

Background: In the Fractional Flow Reserve Versus Angiography for Multivessel Evaluation (FAME) study, fractional flow reserve (FFR)-guided percutaneous coronary intervention (PCI) improved outcome compared with angiography-guided PCI for up to 2 years of follow-up. The aim in this study was to investigate whether the favourable clinical outcome with the FFR-guided PCI in the FAME study persisted over a 5-year follow-up., Methods: The FAME study was a multicentre trial done in Belgium, Denmark, Germany, the Netherlands, Sweden, the UK, and the USA. Patients (aged ≥ 18 years) with multivessel coronary artery disease were randomly assigned to undergo angiography-guided PCI or FFR-guided PCI. Before randomisation, stenoses requiring PCI were identified on the angiogram. Patients allocated to angiography-guided PCI had revascularisation of all identified stenoses. Patients allocated to FFR-guided PCI had FFR measurements of all stenotic arteries and PCI was done only if FFR was 0·80 or less. No one was masked to treatment assignment. The primary endpoint was major adverse cardiac events at 1 year, and the data for the 5-year follow-up are reported here. Analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00267774., Findings: After 5 years, major adverse cardiac events occurred in 31% of patients (154 of 496) in the angiography-guided group versus 28% (143 of 509 patients) in the FFR-guided group (relative risk 0·91, 95% CI 0·75-1·10; p=0·31). The number of stents placed per patient was significantly higher in the angiography-guided group than in the FFR-guided group (mean 2·7 [SD 1·2] vs 1·9 [1·3], p<0·0001)., Interpretation: The results confirm the long-term safety of FFR-guided PCI in patients with multivessel disease. A strategy of FFR-guided PCI resulted in a significant decrease of major adverse cardiac events for up to 2 years after the index procedure. From 2 years to 5 years, the risks for both groups developed similarly. This clinical outcome in the FFR-guided group was achieved with a lower number of stented arteries and less resource use. These results indicate that FFR guidance of multivessel PCI should be the standard of care in most patients., Funding: St Jude Medical, Friends of the Heart Foundation, and Medtronic., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Objectives: The aim of this study was to assess the validity of measuring fractional flow reserve (FFR) of the left main (LM) coronary artery in the setting of concomitant left anterior descending (LAD) or left circumflex (LCX) stenoses., Background: The theoretical impact of a stenosis in the LAD on the FFR assessment of intermediate LM disease with the pressure wire in an unobstructed LCX is currently unknown., Methods: A previously validated in vitro model of the coronary circulation was used to create a fixed intermediate stenosis of the LM and a variable downstream LAD or LCX stenosis. The true LM FFR (FFR(LM true)), with no concomitant downstream disease, was compared to the apparent LM FFR (FFR(LM apparent)), with concomitant downstream disease measured with different degrees of LAD or LCX disease. Additionally, an equation based on a resistors model was derived to predict the effect of downstream stenosis on LM FFR (FFR(LM predicted))., Results: In the setting of isolated moderate LM disease (FFR 0.72 ± 0.08), mild to moderate proximal LAD or LCX lesions did not significantly affect LM FFR. Lesions with a composite FFR (LM + downstream disease) ≥0.65 resulted in an FFR(LM apparent) that was not significantly different from FFR(LM true) (0.76 ± 0.06 vs. 0.76 ± 0.05, p = 0.124). Our equation for FFR(LM predicted) accurately modeled the effects of concomitant disease (r = 0.95, p < 0.001)., Conclusions: These data suggest that in the presence of proximal mild to moderate LAD or LCX disease, LM FFR can be reliably measured with the pressure wire placed in the uninvolved epicardial artery., (Copyright © 2012 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: The aim of this study was to study whether there is a difference in benefit of fractional flow reserve (FFR) guidance for percutaneous coronary intervention (PCI) in multivessel coronary disease in patients with unstable angina (UA) or non-ST-segment elevation myocardial infarction (NSTEMI), compared with stable angina (SA)., Background: The use of FFR to guide PCI has been well established for patients with SA. Its use in patients with UA or NSTEMI has not been investigated prospectively., Methods: In the FAME (Fractional flow reserve versus Angiography for Multivessel Evaluation) study 1,005 patients with multivessel disease amenable to PCI were included and randomized to either angiography-guided PCI of all lesions ≥50% or FFR-guided PCI of lesions with an FFR ≤0.80. Patients admitted for UA or NSTEMI with positive troponin but total creatine kinase <1,000 U/l were eligible for inclusion. We determined 2-year major adverse cardiac event rates of these patients and compared it with stable patients., Results: Of 1,005 patients, 328 had UA or NSTEMI. There was no evidence for heterogeneity among the subgroups for any of the outcome variables (all p values >0.05). Using FFR to guide PCI resulted in similar risk reductions of major adverse cardiac events and its components in patients with UA or NSTEMI, compared with patients with SA (absolute risk reduction of 5.1% vs. 3.7%, respectively, p = 0.92). In patients with UA or NSTEMI, the number of stents was reduced without increase in hospital stay or procedure time and with less contrast use, in similarity to stable patients., Conclusions: The benefit of using FFR to guide PCI in multivessel disease does not differ between patients with UA or NSTEMI, compared with patients with SA., (Copyright © 2011 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)