A novel framework for fluid/structure interaction in rapid subject specific simulations of blood flow in coronary artery bifurcations

Abstract

Background/Aim. Practical difficulties, particularly long model development time, have limited the types and applicability of computational fluid dynamics simulations in numerical modeling of blood flow in serial manner. In these simulations, the most revealing flow parameters are the endothelial shear stress distribution and oscillatory shear index. The aim of this study was analyze their role in the diagnosis of the occurrence and prognosis of plaque development in coronary artery bifurcations. Methods. We developed a novel modeling technique for rapid cardiovascular hemodynamic simulations taking into account interactions between fluid domain (blood) and solid domain (artery wall). Two numerical models that represent the observed subdomains of an arbitrary patient-specific coronary artery bifurcation were created using multi-slice computed tomography (MSCT) coronagraphy and ultrasound measurements of blood velocity. Coronary flow using an in-house finite element solver PAK-FS was solved. Results. Overall behavior of coronary artery bifurcation during one cardiac cycle is described by: velocity, pressure, endothelial shear stress, oscillatory shear index, stress in arterial wall and nodal displacements. The places where (a) endothelial shear stress is less than 1.5, and (b) oscillatory shear index is very small (close or equal to 0) are prone to plaque genesis. Conclusion. Finite element simulation of fluid-structure interaction was used to investigate patient-specific flow dynamics and wall mechanics at coronary artery bifurcations. Simulation model revealed that lateral walls of the main branch and lateral walls distal to the carina are exposed to low endothelial shear stress which is a predilection site for development of atherosclerosis. This conclusion is confirmed by the low values ??of oscillatory shear index in those places.Uvod/Cilj. Prakticne poteskoce, posebno dugo vreme razvoja modela, ogranicavaju tipove i primenljivost racunske dinamike fluida u numerickom modeliranju strujanja krvi za veci broj bolesnika. U ovim simulacijama, parametri strujanja koji najvise pokazuju su endotelijski smicajni napon i oscilujuci smicajni indeks. Cilj rada bio je da se analizira njihova uloga u dijagnozi i prognoziranju razvoja plaka na racvama (bifurkacijama) koronarnih arterija. Metode. Razvili smo novu tehniku kompjuterskog modeliranja za potrebe brzih kardiovaskularnih hemodinamickih simulacija uzimajuci u obzir interakcije izmedju domena fluida (krv) i domena strukture (arterijskog zida). Generisana su dva numericka modela koja predstavljaju posmatrane poddomene bifurkacije koronarne arterije slucajno izabranog bolesnika, koriscenjem multi-slajsne kompjuterizovane tomografije (MSCT) koronarografije i ultrazvucnog merenja brzine strujanja krvi. Simulacija koronarnog strujanja je izvrsena koriscenjem sopstvenog softvera PAK-FS. Rezultati. Sveukupno ponasanje strujanja krvi u bifurkacijama koronarnih arterija je opisano preko sledecih parametara: brzina, pritisak, endotelijski smicajni napon, oscilujuci smicajni indeks, napon na zidu arterije i cvorna pomeranja. Mesta gde je (a) endotelijski smicajni napon manji od 1,5 i (b) oscilujuci smicajni indeks veoma mali (blizak ili jednak 0) su sklona razvoju plaka. Zakljucak. Simulacija interakcije fluida-strukture metodom konacnih elemenata je koriscena da se ispitaju dinamika strujanja krvi i mehanicke karakteristike zida bifurkacije koronarne arterije slucajno izabranog bolesnika. U numerickom modelu je otkriveno da lateralni zidovi glavne grane i lateralni zidovi distalno od karine imaju nizak endotelijski smicajni napon sto je preduslov za razvoj ateroskleroze na tim mestima. Ovaj zakljucak je potvrdjen i niskim vrednostima oscilatornog smicajnog indeksa na istim mestima. PR Projekat Ministarstva nauke Republike Srbije, br. TR32036: Software development for solving coupled multiphysics problems i br. OI175082: Non-invasive and invasive diagnostic and percutaneous treatment of the stenosis of blood vessels branch