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Influence of the position of the distal pressure measurement point on the Fractional Flow Reserve using in-silico simulations

Agujetas Rafael, Ferrera Conrado, González-Fernández Reyes, Nogales-Asensio Juan M., Fernández-Tena Ana

Biocybernetics and Biomedical Engineering

2023

Vol. 43, no. 1

69--81

Coronary stenosis is mainly responsible for myocardial ischemia as the blood supply to a portion of the heart stops or is severely reduced. The Fractional Flow Reserve is the benchmark for the hemodynamic significance assessment of coronary stenoses. Its value is employed as a gatekeeper/planning tool for revascularization in clinical practice. Non-invasive alternatives have been successfully proposed to guide cardiologists. However, simulation values are not accurate enough in the 0.75-0.85 range, so invasive Fractional Flow Reserve should be used. Several authors argue about where distal pressure should be measured. Therefore, our aim is to use simulation to assess how this value changes and to detect the correct measurement region. First, we have adjusted the simulation method to the segmentations of two patients whose invasive Fractional Flow Reserve is known. We then extended our analysis to four patients and obtained the simulated value at multiple points distal to the stenosis. This is an advantage over invasive measurements, whose locations are restricted. The results are also essential for locating the best region for invasive distal pressure measurements. We propose a hybrid invasive and in-silico procedure that would avoid false results and prevent cardiologists from making erroneous clinical decisions.

Patient-specific fluid-structure interaction simulation of the LAD-ITA bypass graft for moderate and severe stenosis: A doubt on the fractional flow reserve-based decision

Tajeddini Farshad, Firoozabadi Bahar, Pakravan Hossein Ali, Ahmadi Tafti Seyed Hossein

Biocybernetics and Biomedical Engineering

2022

Vol. 42, no. 1

143--157

Fractional flow reserve (FFR)-based decision improves the outcomes of percutaneous coronary intervention (PCI) for some patients, while its effectiveness in improving the results of coronary artery bypass graft (CABG) is unclear, in particular for moderate stenosis. It may be due to the fact that FFR cannot take into account the impacts of competitive flow (CF), intimal hyperplasia (IH), as well as compliance mismatch (CMM). As a result, two questions arise 1) whether FFR is a sufficient factor to decide to perform the CABG for patients with moderate to severe stenosis or not and 2) whether post-operative FFR shows the effectiveness of a graft. To shed light on this matter, two patient-specific models of LAD-ITA graft, consisting of two different severities of stenosis (moderate and severe), were simulated using two-way FSI simulation. It was observed that although both pre- and postoperative FFRs for moderate stenosis were higher, CF is more intense for moderate stenosis than severe one. Also, it was seen that CM and IH are more likely to occur in the bed, toe, and heel areas of a bypass graft performed for moderate stenosis. All in all, it can be concluded that in the case of moderate stenosis, pre- and post-operative FFRs might not be a suitable index for making the decision about performing or deferring CABG and also the effectiveness of the graft. Under such circumstances, it seems rational to use CFD in a wider range to investigate patients with moderate stenosis before the operation.