“…This will allow us to identify, for example, the most important risk factors of hemolysis after a TAVI procedure. The recent study by Laflamme et al 19 identifies wall shear rate 9 and the energy loss index 27 as risk factors in patient with severe prosthesispatient mismatch. Numerical simulations have the theoretical advantage over experimental studies for the investigation of TAVR to overcome the limit of the spatial resolution, 2,35 which makes the evaluation of many in vivo flow and structural characteristics very difficult.…”
Section: Discussionmentioning
confidence: 98%
“…Like in other cardiovascular fields, in silico models have been applied to better understand the mechanics and hemodymanics of devices and treated vessels; in the aortic root pathologies they are emerging as useful tools for the prediction and the interpretation of the phenomena involved and for the design optimization to increase durability and reduce several risk factors such as obstruction of coronary arteries, valve regurgitation 34 and hemolyis. 19 The behavior of a percutaneous valve is influenced either by the mechanics of the aortic root, the leaflets and the stent frame as well as the fluid passing through the site where the valve is implanted. Experimental studies for the investigation of TAVR have a low spatial resolution 2,35 and many flow and structural characteristics either cannot be evaluated, or can only be evaluated with difficulty.…”
Transcatheter aortic valve replacement (TAVR) represents an established recent technology in a high risk patient base. To better understand TAVR performance, a fluid-structure interaction (FSI) model of a self-expandable transcatheter aortic valve was proposed. After an in vitro durability experiment was done to test the valve, the FSI model was built to reproduce the experimental test. Lastly, the FSI model was used to simulate the virtual implant and performance in a patient-specific case. Results showed that the leaflet opening area during the cycle was similar to that of the in vitro test and the difference of the maximum leaflet opening between the two methodologies was of 0.42%. Furthermore, the FSI simulation quantified the pressure and velocity fields. The computed strain amplitudes in the stent frame showed that this distribution in the patient-specific case is highly affected by the aortic root anatomy, suggesting that the in vitro tests that follow standards might not be representative of the real behavior of the percutaneous valve. The patient-specific case also compared in vivo literature data on fast opening and closing characteristics of the aortic valve during systolic ejection. FSI simulations represent useful tools in determining design errors or optimization potentials before the fabrication of aortic valve prototypes and the performance of tests.
“…This will allow us to identify, for example, the most important risk factors of hemolysis after a TAVI procedure. The recent study by Laflamme et al 19 identifies wall shear rate 9 and the energy loss index 27 as risk factors in patient with severe prosthesispatient mismatch. Numerical simulations have the theoretical advantage over experimental studies for the investigation of TAVR to overcome the limit of the spatial resolution, 2,35 which makes the evaluation of many in vivo flow and structural characteristics very difficult.…”
Section: Discussionmentioning
confidence: 98%
“…Like in other cardiovascular fields, in silico models have been applied to better understand the mechanics and hemodymanics of devices and treated vessels; in the aortic root pathologies they are emerging as useful tools for the prediction and the interpretation of the phenomena involved and for the design optimization to increase durability and reduce several risk factors such as obstruction of coronary arteries, valve regurgitation 34 and hemolyis. 19 The behavior of a percutaneous valve is influenced either by the mechanics of the aortic root, the leaflets and the stent frame as well as the fluid passing through the site where the valve is implanted. Experimental studies for the investigation of TAVR have a low spatial resolution 2,35 and many flow and structural characteristics either cannot be evaluated, or can only be evaluated with difficulty.…”
Transcatheter aortic valve replacement (TAVR) represents an established recent technology in a high risk patient base. To better understand TAVR performance, a fluid-structure interaction (FSI) model of a self-expandable transcatheter aortic valve was proposed. After an in vitro durability experiment was done to test the valve, the FSI model was built to reproduce the experimental test. Lastly, the FSI model was used to simulate the virtual implant and performance in a patient-specific case. Results showed that the leaflet opening area during the cycle was similar to that of the in vitro test and the difference of the maximum leaflet opening between the two methodologies was of 0.42%. Furthermore, the FSI simulation quantified the pressure and velocity fields. The computed strain amplitudes in the stent frame showed that this distribution in the patient-specific case is highly affected by the aortic root anatomy, suggesting that the in vitro tests that follow standards might not be representative of the real behavior of the percutaneous valve. The patient-specific case also compared in vivo literature data on fast opening and closing characteristics of the aortic valve during systolic ejection. FSI simulations represent useful tools in determining design errors or optimization potentials before the fabrication of aortic valve prototypes and the performance of tests.
“…8), vortex generation and the presence of recirculation areas. In addition, the determination of shear stresses is very important as a risk factor for hemolysis (Laflamme et al, 2015). Fig.…”
Bio-inspired polymeric heart valves (PHVs) are excellent candidates to mimic the structural and the fluid dynamic features of the native valve. PHVs can be implanted as prosthetic alternative to currently clinically used mechanical and biological valves or as potential candidate for a minimally invasive treatment, like the transcatheter aortic valve implantation. Nevertheless, PHVs are not currently used for clinical applications due to their lack of reliability. In order to investigate the main features of this new class of prostheses, pulsatile tests in an in-house pulse duplicator were carried out and reproduced in silico with both structural Finite-Element (FE) and Fluid-Structure interaction (FSI) analyses. Valve kinematics and geometric orifice area (GOA) were evaluated to compare the in vitro and the in silico tests. Numerical results showed better similarity with experiments for the FSI than for the FE simulations. The maximum difference between experimental and FSI GOA at maximum opening time was only 5%, as compared to the 46.5% between experimental and structural FE GOA. The stress distribution on the valve leaflets clearly reflected the difference in valve kinematics. Higher stress values were found in the FSI simulations with respect to those obtained in the FE simulation. This study demonstrates that FSI simulations are more appropriate than FE simulations to describe the actual behaviour of PHVs as they can replicate the valve-fluid interaction while providing realistic fluid dynamic results.
“…Laflamme et al reported incidence of hemolysis after TAVI at 14.8%, but no patient required transfusion. 27 There has been no report assessing the clinical impact of hemolysis after TAVI.…”
Section: Percutaneous Closure As a Treatment Option For Paravalvular mentioning
Paravalvular regurgitation (PVR) remains one of the drawbacks of transcatheter aortic valve implantation (TAVI). Details of percutaneous closure (PCC) of PVR after TAVI remain obscure. We aimed to explore the patient characteristics, procedural details, closure devices used, and outcomes of PCC after TAVI. A systematic search of the MEDLINE/PubMed and Embase databases from January 2002 to September 2015 was conducted. Reports considered to include same patient were excluded and only the studies with largest cohorts were included. A total of 14 studies including 58 patients (61 cases) were included in the study. A balloonexpandable (BE) valve was used more frequently compared with a self-expandable (SE) valve (72.6% vs 27.4%, respectively). The mean success rate was 86.9% (100% and 77.8%, respectively; P = 0.097). The median number of closure devices used was 1 (range, 1-4) and did not differ between SE and BE valves (P = 0.71). Mean time from index procedure to PCC did not differ between SE and BE valves (295 ± 380 days vs 379 ± 353 days; P = 0.71). Seven patients had history of valve-in-valve and 6 patients had procedural success. Among the patients with available follow-up data (94.8%), there were 15 deaths (27.3%). Percutaneous closure of PVR after TAVI had a high success rate in selected patients in both BE and SE valves. The success rate, timing, and number of closure devices were similar between BE and SE valves. However, prognosis remains fairly poor.
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