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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.

Metody oceny rezerwy wieńcowej

Gawryś K., Gawryś J., Majchrzak K.

Inżynier i Fizyk Medyczny

2016

Vol. 5, nr 6

335--341

Rezerwa wieńcowa, będąca różnicą pomiędzy spoczynkowym a maksymalnym przepływem wieńcowym, a także cząstkowa rezerwa przepływu są przydatnymi parametrami w ocenie pacjentów z chorobą wieńcową i ich kwalifikacji do leczenia zachowawczego bądź rewaskularyzacyjnego. Pośrednie metody oceny rezerwy wieńcowej – próby ergometryczne pozwalają m.in. na ocenę zdolności krążenia wieńcowego do dostarczania odpowiedniej ilości tlenu w sytuacji zwiększonego zapotrzebowania. Do oceny perfuzji mięśnia sercowego i rezerwy wieńcowej wykorzystuje się także skalę TIMI (Thrombolysis in Myocardial Infarction) i jej modyfikacje przydatne w prognozowaniu rokowania u chorych z ostrym zawałem serca oraz w ocenie efektów leczenia reperfuzyjnego, rezonans magnetyczny pozwalający dodatkowo na zbadanie innych parametrów funkcjonalnych serca, SPECT (Single-photon Emission Computed Tomography), PET (Positron Emission Tomography), a także nowoczesne skanery PET-CT i SPECT-CT.

Coronary reserve, defined as the difference between resting and maximum coronary flow, as well as the fractional flow reserve are useful parameters in the evaluation of patients with coronary artery disease and their qualifications to conservative or invasive treatment. Indirect methods of coronary reserve assessment – ergometric tests, allow to assess the capacity to deliver enough amount of oxygen in the case of increased demand. To assess myocardial perfusion and coronary reserve are also used: TIMI (Thrombolysis in Myocardial Infarction) scale – useful in predicting prognosis in patients with acute myocardial infarction and in evaluating the effects of reperfusion therapy, magnetic resonance imaging which allows also to explore other functional parameters of the heart, SPECT (Single-Photon Emission Computed Tomography), PET (Positron Emission Tomography) and modern scanners – PET-CT and SPECT-CT.