Pulse Duplicator Research Articles

Flow Dynamics in Anomalous Aortic Origin of a Coronary Artery in Children: Importance of the Intramural Segment

This study aims to assess the differences in pressure, fractional flow reserve (FFR) and coronary flow (with increasing pressure) of the proximal coronary artery in patients with anomalous aortic origin of a coronary artery with a confirmed ischemic event, without ischemic events, and before and after unroofing surgery, and compare to a patient with normal coronary arteries. Patient-specific flow models were 3D printed for 3 subjects with anomalous right coronary arteries with intramural course, 2 of them had documented ischemia, and compared with a patient with normal coronaries. The models were placed in the aortic position of a pulse duplicator and precise measurements to quantify FFR and coronary flow rate were performed from the aortic to the mediastinal segment of the anomalous right coronary artery. In an ischemic model, a gradual FFR drop (emulating that of pressure) was shown from the ostium location (∼1.0) to the distal intramural course (0.48). In nonischemic and normal patient models, FFR for all locations did not drop below 0.9. In a second ischemic model prior to repair, a drop to 0.44 was encountered at the intramural and mediastinal intersection, improving to 0.86 postrepair. There is a difference in instantaneous coronary flow rate with increasing aortic pressure in the ischemic models (slope 0.2846), compared to the postrepair and normal models (slope >0.53). These observations on patient models support a biomechanical basis for ischemia and potentially sudden cardiac death in aortic origin of a coronary artery, with a drop in pressure and FFR in the intramural segment, and a decrease in coronary flow rate with increasing aortic pressure, with both improving after corrective surgery.

Bioprosthetic aortic valve diameter and thickness are directly related to leaflet fluttering: Results from a combined experimental and computational modeling study

ObjectiveBioprosthetic heart valves (BHVs) are commonly used in surgical and percutaneous valve replacement. The durability of percutaneous valve replacement is unknown, but surgical valves have been shown to require reintervention after 10 to 15 years. Further, smaller-diameter surgical BHVs generally experience higher rates of prosthesis–patient mismatch, which leads to higher rates of failure. Bioprosthetic aortic valves can flutter in systole, and fluttering is associated with fatigue and failure in flexible structures. The determinants of flutter in BHVs have not been well characterized, despite their potential to influence durability. MethodsWe use an experimental pulse duplicator and a computational fluid-structure interaction model of this system to study the role of device geometry on BHV dynamics. The experimental system mimics physiological conditions, and the computational model enables precise control of leaflet biomechanics and flow conditions to isolate the effects of variations in BHV geometry on leaflet dynamics. ResultsBoth experimental and computational models demonstrate that smaller-diameter BHVs yield markedly higher leaflet fluttering frequencies across a range of conditions. The computational model also predicts that fluttering frequency is directly related to leaflet thickness. A scaling model is introduced that rationalizes these findings. ConclusionsWe systematically characterize the influence of BHV diameter and leaflet thickness on fluttering dynamics. Although this study does not determine how flutter influences device durability, increased flutter in smaller-diameter BHVs may explain how prosthesis–patient mismatch could induce BHV leaflet fatigue and failure. Ultimately, understanding the effects of device geometry on leaflet kinematics may lead to more durable valve replacements.

Impact of aortic annulus geometry according to ISO 5840:2019 (draft) on hydrodynamic performance of transcatheter aortic valve prostheses

Abstract To assess the hydrodynamic performance of transcatheter aortic valve prostheses (TAVP), in vitro test using pulse duplicators is required. Test conditions as well as minimum performance criteria are specified in ISO 5840- 3:2013 and ISO 5840-3:2019-draft. In the 2019 published draft, modifications regarding hydrodynamic testing are proposed. Among others, the geometrical configuration of the fixation has changed, with the intention to improve the anatomical representation as well as the comparability of results from different test laboratories. We analyzed the consequences of altered annulus fixations regarding native leaflets as well as a step in the proximal area of the protheses to prevent their migration. The analyses were conducted with regard to the degree of calcification of the annulus ring on hydrodynamic parameters. By using 3D stereolithography printing technology, molds for casting of silicone elastomer of annulus models with and without native leaflets were manufactured. A modular system enabled us to use the same annulus ring to model the degree of calcification as well as different step sizes. We performed in vitro hydrodynamic testing according to ISO 5840-3:2019-draft of a selfexpandable valve prototype with porcine pericardial leaflets by using a commercially available pulse duplicator system. As expected, regurgitation increases with increasing degree of calcification, whereby the use of a step has no influence on the backflow of fluid during diastole. The effective orifice area (EOA) of the valve showed a clear tendency with respect to radial protrusion of the step. The EOA decreased as the radial protrusion increased. We also present a suggestion to prevent migration without affecting the general test results, by using a novel step design. We also found that the novel annulus model with native leaflet drastically reduced the regurgitation.

A Mathematical Model for Estimating Physiological Parameters of Blood Flow through Rotary Blood Pumps

A mathematical model for estimating physiological parameters of blood flow through rotary blood pumps has been developed. The model is based on the flow–pressure head characteristics of the Sputnik pediatric rotary blood pump measured under static and dynamic conditions, which allows it to cover a wide range of states of the cardiovascular system. The model provides sensorless estimation of the flow–pressure head characteristics. For the Sputnik pediatric rotary blood pump, the accuracy of estimation of the flow and the pressure head averaged over a single cardiac cycle is R2 = 0.998 and R2 = 0.976, respectively. A ViVitro Pulse Duplicator SD2001-1 bench (ViVitro Inc., Victoria, Canada) has been used to verify the developed mathematical model. The verification yielded the following values of accuracy of estimation of parameters averaged over a single cardiac cycle: flow rate, R2 = 0.993; pressure head, R2 = 0.994.

Hemodynamics inside the neo- and native sinus after TAVR: Effects of implant depth and cardiac output on flow field and coronary flow.

Transcatheter aortic valve replacement (TAVR) has emerged as a widely used therapy for aortic valve diseases. With TAVR, flow hemodynamics may change leading to areas of flow stagnation prone to thrombosis risk. The neo-sinus, created by introducing a prosthesis inside the diseased native valve, may prompt leaflet thrombosis due to areas of flow stasis. This study attempted to understand the effect of different prosthesis implant depths on the flow field within the neo- and native sinus and on the coronary perfusion. Experiments were performed inside an in vitro pulse duplicator producing physiological conditions according to ISO 5840-1:2015 standard. Flow fields were obtained for two cardiac outputs (CO) using particle image velocimetry (PIV). Washout was calculated as a measure of flow stasis. The two main results are: a lower implant position and a lower CO/frequency led to better native sinus washout, but worsened neo-sinus washout. In contrast, a higher implant position led to higher coronary flow (for higher CO/frequency). No significant effect of implant depth on coronary flow was observed for lower CO/frequency. In summary, a higher implant position using this self-expanding prosthesis is associated with reduced neo-sinus flow stasis. Hereby, washout of the native sinus, as well as coronary flow, are dependent on cardiac output.

High complexity femtosecond pulse duplicator.

This paper presents a theoretical and numerical study of a 0-π fan-out phase grating placed in the Fourier plane of a spatio-spectral pulse shaper followed by a spherical focusing lens. It is shown that this device acts as a high complexity femtosecond pulse duplicator designed for two source interferometry. At the focus of the lens, the electric field displays two spatially separated intense spots in which relative delay can be continuously tuned over 4 orders of magnitude, typically from a few attoseconds to a few tens of femtoseconds. Because the two pulses do not spatially overlap, their intensity remains unchanged when the relative delay is smaller than the pulse duration. Detailed simulations of the shaped electric field are presented.

Hydrodynamic performance of a novel suturelessprosthetic aortic valve

The aimof the study was an in vitro hydrodynamic study of the developed prosthetic heart valve of the second generation, designed to carry out an implantation using «valve-in-valve» method.Material and methods.Prototypes of the developed prosthesis were studied under simulated physiological conditions of the heart using a Vivitro Labs pulse duplicator (Canada) in a comparative aspect with «UniLine» clinical commercial aortic valve bioprosthesis (Russia). Samples were tested by simulating sutureless implantation procedure.Results. The developed valves showed satisfactory hydrodynamic characteristics – for all cases of «implantation» from the position of the average trans-prosthetic gradient (6.1–11.1 mm Hg) and the effective orifice area (1.60–1.81 cm2 ). The analysis of the regurgitation fraction allowed us to determine the optimal sizes for implantation using «valvein-valve» method, which subsequently will form the basis of sizing guidelines for size selection. A qualitative analysis of the leaflet’s work demonstrated the presence of slight asymmetry for a number of prostheses – in case of mismatch of sizes when simulating «valve-in-valve» procedure.Conclusion. The tests demonstrate the viability of the developed design from the standpoint of hydrodynamic efficiency and determines the basic rules of selecting a prosthesis for reimplantation relative to the primary valve.

Impact of superhydrophobicity on the fluid dynamics of a bileaflet mechanical heart valve

ObjectiveThe objective of this study is to evaluate the impact of superhydrophobic coating on the hemodynamics and turbulence characteristics of a bileaflet mechanical valve in the context of evaluating blood damage potential. MethodsTwo 3D printed bileaflet mechanical valves were hemodynamically tested in a pulse duplicator under physiological pressure and flow conditions. The leaflets of one of the two valves were sprayed with a superhydrophobic coating. Particle Image Velocimetry was performed. Pressure gradients (PG), effective orifice areas (EOA), Reynolds shear stresses (RSS) and instantaneous viscous shear stresses (VSS) were calculated. Results(a) Without SH coating, the PG was found to be 14.53 ± 0.7 mmHg and EOA 1.44 ± 0.06 cm2. With coating, the PG obtained was 15.21 ± 1.7 mmHg and EOA 1.39 ± 0.07 cm2; (b) during peak systole, the magnitude of RSS with SH coating (110Pa) exceeded that obtained without SH coating (40 Pa) with higher probabilities to develop higher RSS in the immediate wake of the leaflet; (c) The magnitudes range of instantaneous VSS obtained with SH coating were slightly larger than those obtained without SH coating (7.0 Pa versus 5.0 Pa). ConclusionWith Reynolds Shear Stresses and instantaneous Viscous Shear Stresses being correlated with platelet damage, SH coating did not lead to their decrease. While SH coating is known to improve surface properties such as reduced platelet or clot adhesion, the relaxation of the slip condition does not necessarily improve overall hemodynamic performance for the bileaflet mechanical valve design.

4242 Evaluating the effect of a compliant stent-graft prototype on effective stiffness in a cadaveric aorta

OBJECTIVES/GOALS: High aortic stiffness is associated with increased cardiovascular morbidity and mortality. The purpose of this work is to demonstrate the potential of our compliant stent-graft design to therapeutically increase aortic compliance over a standard aortic stent-graft. METHODS/STUDY POPULATION: The aorta from a human cadaver will be excised and placed into a pulse duplicator circuit. The stiffness of the system will be estimated using the pulse wave velocity (PWV), which will be calculated using the time delay between pressure measurements at proximal and distal locations in the system. Baseline measurements with the unstented aorta will be compared to two cases: (1) with a standard stent-graft placed, and (2) with our compliant stent-graft prototype in the descending thoracic aorta. PWV is calculated as the distance between the pressure sensors divided by the time delay. Faster PWV is associated with a stiffer vessel, or lower aortic compliance. RESULTS/ANTICIPATED RESULTS: Prior work in vitro showed that the compliant stent-graft reduced peak and pulse pressures compared a standard, rigid stent-graft. We also expect the compliant device to exhibit lower PWV compared to a rigid stent-graft. Depending on the aortic tissue stiffness, the compliant stent-graft could raise or lower PWV compared to no stent. Mean pressure in the compliant case is likely to be slightly higher than the other two cases because the compliant stent-graft’s narrower lumen increases flow resistance. Although mean pressure will be higher, peak pressure should be lower than in the standard stent-graft because the added compliance decreases overall pressure swing between systole and diastole. DISCUSSION/SIGNIFICANCE OF IMPACT: Lower PWV in the compliant stent-graft over the standard stent-graft will indicate its potential to therapeutically lower aortic stiffness in patients needing aortic stenting. Positive outcomes from this study will be a step toward the eventual translation of a compliant stent-graft to clinical use.

Sinus Hemodynamics After Transcatheter Aortic Valve in Transcatheter Aortic Valve

This study evaluated the effect of transcatheter aortic valve (TAV)-in-TAV on sinus hemodynamics and washout. With TAV becoming the standard procedure for aortic valve replacement and with the limited valve durability, a second intervention is necessary (TAV-in-TAV) after first TAV failure. Six arrangements of TAV-in-TAV were chosen for this study as follows: (1) Evolut 23 (Medtronic, Minneapolis, MN) in Evolut 26, (2) Evolut 23 in SAPIEN 3 23 (Edwards Lifesciences, Irvine, CA), (3) Evolut 26 in Evolut 26, (4) Evolut 26 in SAPIEN 23, (5) SAPIEN 3 23 in Evolut 26, and (6) SAPIEN 3 23 in SAPIEN 3 23. These TAV-in-TAV configurations were assessed in a pulse duplicator. Particle image velocimetry was performed. During systole, (1) the highest velocity was found with SAPIEN-in-SAPIEN (0.7 m/s) and the lowest was with Evolut 26-in-Evolut 26 (0.2 m/s); (2) the highest shear stress magnitude near the leaflet was with Evolut 23-in-SAPIEN (1.45 Pa) and the lowest was with Evolut 26-in-Evolut 26 (0.55 Pa); and (3) washout was almost equal in all sinuses of these cases (<2.5 cycles). This study shows that TAV-in-TAV is highly dependent on the valve that is originally implanted and the valve to be implanted. Washout is not significantly degraded after TAV-in-TAV compared with valve-in-valve and TAV replacement. Further studies are needed to optimize valve size and selection.

A bench test study of bioprosthetic valve fracture performed before versus after transcatheter valve-in-valve intervention.

Bioprosthetic valve fracture (BVF) may improve transvalvular gradients and transcatheter heart valve (THV) expansion during VIV interventions. However, the optimal timing of BVF is unknown. We assessed the impact of timing of BVF (before versus after) for valve-in-valve (VIV) intervention, on hydrodynamic function and THV expansion. Three THV designs were assessed, a 23 mm SAPIEN 3 (S3), small ACURATE neo (ACn) and 23 mm Evolut R, deployed into 21 mm Mitroflow bioprosthetic surgical valves. We evaluated each THV in three groups: 1) no BVF, 2) BVF before VIV, and 3) BVF after VIV. Hydrodynamic testing was performed using a pulse duplicator to ISO 5840:2013 standard. Transvalvular gradients were lower when BVF was performed after VIV for the S3 (no BVF 15.5 mmHg, BVF before VIV 8.0 mmHg, BVF after VIV 5.6 mmHg), and the ACn (no BVF 9.8 mmHg, BVF before VIV 8.4 mmHg, BVF after VIV 5.1 mmHg). Transvalvular gradients were similar for the Evolut R, irrespective of performance of BVF or timing of BVF. BVF performed after VIV resulted in better expansion in all three THV designs. The ACn and Evolut R samples all had a mild degree of pinwheeling, and BVF timing did not impact on pinwheeling severity. The S3 samples had severe pinwheeling with no BVF, and significant improvement in pinwheeling when BVF was performed after VIV. BVF performed after VIV was associated with superior THV expansion in all three THV designs tested, with lower residual transvalvular gradients in the S3 and ACn THVs. The Evolut R had similar hydrodynamic performance irrespective of BVF timing. Timing of BVF has potential implications on THV function.

Effects of hemodynamic conditions and valve sizing on leaflet bending stress in self-expanding transcatheter aortic valve: An in vitro study.

Transcatheter aortic valve (TAV) replacement has become a viable alternative to surgery for high and intermediate risk patients with severe aortic stenosis. This technology may extend to the younger and lower risk patients. In this population, long-term durability of the TAV is key. Increased leaflet mechanical stress is one of the main determinants of valve structural deterioration. This in vitro study aims at evaluating leaflet bending stress (LBS) in the self-expanding TAV for different valve sizes, stroke volumes (SV), and degrees of valve oversizing (OS). Three different sizes (23, 26, and 29 mm) of CoreValve (CV) were tested on a pulse duplicator in annulus size ranging from 17 to 26 mm. Leaflet bending stress and bending of the leaflet coaptation line in diastole pinwheeling index (PI) were measured using high-speed camera imaging (1000 images/s). For each given CV and annulus size, geometric orifice area (GOA) increased significantly with OS (P<.001) and SV (P=.001). LBS decreased with increasing prosthesis size and aortic annulus (AA) size while increasing with SV (P<.03). The largest value of peak LBS (3.79 MPa) was obtained with the CV 23 mm in AA of 17 mm (%OS=35%), SV 90 mL and the smallest value (0.99 MPa) for the CV 29 mm in AA of 26 mm (%OS=12%), SV 30 mL. On multivariable analysis, LBS increased independently with larger OS, smaller AA size and higher SV. The PI increased with decreasing AA size and increasing OS. Moderate valve OS, such as generally used for transcatheter aortic valve implantation, is associated with increased LBS during valve opening and closing, especially in small annuli. Hence, TAV OS may negatively impact long-term valve durability.

Fetal Transcatheter Trileaflet Heart Valve Hemodynamics: Implications of Scaling on Valve Mechanics and Turbulence.

The scarcity of data available on the best approach for pulmonary fetal valve replacement or implantation necessitate an investigation on whether practices using adult transcatheter valves could be translated to fetal applications. The objective of this study is to evaluate the hemodynamic characteristics and the turbulent properties of a fetal sized trileaflet transcatheter pulmonary valve in comparison with an adult balloon-expandable valve in order to assess the possibility of designing valves for fetal applications using dynamic similarity. A 6mm fetal trileaflet valve and a 26mm SAPIEN 3valve were assessed in a pulse duplicator. Particle image velocimetry was performed. Pressure gradient (ΔP), effective orifice area (EOA), regurgitant fractions (RF), pinwheeling indices (PI) and turbulent stresses were evaluated. ΔP was 8.56 ± 0.139 and 7.76 ± 0.083mmHg with fetal valve and SAPIEN respectively (p < 0.0001); EOA was 0.10 ± 0.0007 and 2.1 ± 0.025cm2 with fetal valve and SAPIEN respectively (p < 0.0001); RF with the fetal valve was 2.35 ± 1.99% and with SAPIEN 10.92 ± 0.11% (p < 0.0001); PI with fetal valve was 0.404 ± 0.01 and with SAPIEN 0.37 ± 0.07; The flow regime with the fetal valve was turbulent and Reynolds numbers reached about 7000 while those with the SAPIEN reached about 20,000 at peak velocity. Turbulent stresses were significantly higher with fetal valve compared with SAPIEN. Instantaneous viscous shear stresses with fetal valve were 5.8 times higher than those obtained with SAPIEN and Reynolds shear stresses were 2.5 times higher during peak systole. The fetal valve implantation leads to a turbulent flow (specific to this particular type and design of valve) regime unlike what is expected of a small valve with different flow properties compared to adult valves.

Biomechanical simulations and 3D printing for endovascular device testing

Endovascular aortic repair is a minimally invasive procedure to treat aortic diseases such as aneurysms and dissections. Thanks to technological advancements, such procedure has steadily shifted from the abdominal aorta towards the ascending part, i.e., near the heart, calling for an extensive and comprehensive benchmarking of (novel) endografts. Given such considerations, we have exploited porcine aorta with a pulse duplicator to analyse the mechanical interaction between the endovascular device and the native tissue. Our results have implications for using the porcine aorta as a model for human aorta in research. Particularly, the combination of in vitro tests performed using ex-vivo tissue, integrated validated patient-specific numerical simulations, mock arteries manufactured by 3D printing, can offer important insight on biomechanical impact of endograft design on post-operative aortic mechanical response.

Fluid\u2013Structure Interaction Models of Bioprosthetic Heart Valve Dynamics in an Experimental Pulse Duplicator

Computer modeling and simulation is a powerful tool for assessing the performance of medical devices such as bioprosthetic heart valves (BHVs) that promises to accelerate device design and regulation. This study describes work to develop dynamic computer models of BHVs in the aortic test section of an experimental pulse-duplicator platform that is used in academia, industry, and regulatory agencies to assess BHV performance. These computational models are based on a hyperelastic finite element extension of the immersed boundary method for fluid–structure interaction (FSI). We focus on porcine tissue and bovine pericardial BHVs, which are commonly used in surgical valve replacement. We compare our numerical simulations to experimental data from two similar pulse duplicators, including a commercial ViVitro system and a custom platform related to the ViVitro pulse duplicator. Excellent agreement is demonstrated between the computational and experimental results for bulk flow rates, pressures, valve open areas, and the timing of valve opening and closure in conditions commonly used to assess BHV performance. In addition, reasonable agreement is demonstrated for quantitative measures of leaflet kinematics under these same conditions. This work represents a step towards the experimental validation of this FSI modeling platform for evaluating BHVs.

Bio-inspired anisotropic polymeric heart valves exhibiting valve-like mechanical and hemodynamic behavior

Native heart valve leaflets with layered fibrous structures show anisotropic characteristics, allowing them to withstand complex mechanical loading for long-term cardiac cycles. Herein, two types of silk fibroin (SF) fiber membranes with anisotropic (ASF) and isotropic (ISF) properties were prepared by electrospinning, and were further combined with poly(ethylene glycol) diacrylate (PEGDA) hydrogels to serve as polymeric heart valve (PHV) substitutes (PEGDA-ASF and PEGDA-ISF). The uniaxial tensile tests showed obvious anisotropy of PEGDA-ASF with elastic moduli of 10.95±1.09 and 3.55± 0.32 MPa, respectively, along the directions parallel and perpendicular to the fiber alignment, while PEGDA-ISF possessed isotropic property with elastic moduli of 4.54± 0.43 MPa. The PHVs from both PEGDA-ASF and PEGDA-ISF presented appropriate hydrodynamic properties from pulse duplicator tests according to the ISO 5840-3 standard. However, finite element analysis (FEA) revealed the anisotropic PEGDA-ASF valve showed a lower maximum principle stress value (2.20 MPa) in commissures during diastole compared with that from the isotropic PEGDA-ISF valve (2.37 MPa). In the fully open state, the bending area of the PEGDA-ASF valve appeared in the belly portion and near the attachment line like native valves, however, which was close to free edges for the PEGDA-ISF valve. The Gauss curvature analysis also indicated that the anisotropic PEGDA-ASF valve can produce appropriate surface morphology by dynamically adjusting the movement of bending area during the opening process. Hence, anisotropy of PHVs with bio-inspired layered fibrous structures played important roles in mechanical and hydrodynamic behavior mimicking native heart valves.

Differences in Pressure Recovery Between Balloon Expandable and Self-expandable Transcatheter Aortic Valves.

Pressure recovery downstream of the aortic valve constitutes an important factor affecting the calculation of pressure gradient (PG) across the valve and therefore the accuracy of the calculated aortic valve area. Some clinical studies hypothesized that stent and valve cusps design contribute to flow acceleration and Doppler-measured valve gradients across the balloon-expandable transcatheter aortic valve. This study aims at elucidating the physical mechanisms behind pressure recovery variations between Edwards SAPIEN 3 and Medtronic Evolut TAVs through the measurements of sensitive and precise axial pressure profiles. A 23mm Edwards SAPIEN3 and a 26mm Medtronic Evolut were deployed in a pulse duplicator. A Millar catheter was used to record 50 cycles of pressure data along the centerline of the valve chamber upstream and downstream of the valve. The peak PG obtained with SAPIEN at vena contracta (VC) is 18.83 ± 0.75mmHg and after recovery, 9.56 ± 0.78mmHg. For Evolut at VC, peak PG is 18.25 ± 0.63mmHg and after recovery, 10.3 ± 0.57mmHg. The differences in peak PG at VC and at the recovery were statistically significant (p < 0.001). With SAPIEN 3 at VC, the mean PG obtained is 10.11 ± 0.63mmHg and after recovery 7.06 ± 0.46mmHg. For Evolut, mean PG at VC is 10.45 ± 0.67mmHg and after recovery 7.99 ± 0.61mmHg. The differences between the mean PG between the two valves was not statistically significant at VC (p = 0.71) but significant post-recovery (p < 0.00001). While gradients at the VC are higher with the SAPIEN 3, the net gradient after pressure recovery is significantly lower compared to Evolut TAV. Efficiency ofpressure recovery significantly depends on valve type due tostent interference with the recovering blood flow.

In-vitro characterization of self-expandable textile transcatheter aortic valves

ObjectiveThis study aims at assessing the global dynamic behavior, closing energy and turbulence characteristics of self-expandable textile (inclined and straight yarn) transcatheter aortic valves (TAV) versus bioprosthetic TAVs. MethodsTwo self-expandable textile TAVs one with inclined yarn textile and another with straight yarn textile leaflets were assessed in a pulse duplicator and compared with a self-expandable commercial bioprosthetic TAV under physiological pressure and flow. Particle Image Velocimetry and high-speed imaging were performed. Effective orifice areas (EOA), leakage fractions (LF), Pinwheeling indices (PI), closing energy (E), viscous shear stresses (VSS) and Reynolds shear stresses (RSS) were calculated. Results(a) EOAs and LFs were 2.27 ± 0.03 cm2, 31.7 ± 0.6%; 2.25 ± 0.08 cm2, 26.6 ± 0.7%; and 1.63 ± 0.01 cm2, 29.1 ± 1.25% for inclined textile, bioprosthetic and straight textile TAV respectively (p < 0.0001). (b) Following same order, PIs were significantly different going from 1.16 ± 0.21%, 8.48 ± 0.8% and 8.865 ± 0.58% with the exception of CoreValve and straight yarn valve (p = 0.37); (c) E is lowest for straight textile TAV (0.0024 ± 0.0017 J), followed by bioprosthetic valve (0.00259 ± 0.0011 J) and then 45° Oriented Yarn Valve (0.00334 ± 0.03 J) (d) At peak systole, the highest RSS distribution was with the Straight textile TAV reaching up to 330Pa. The bioprosthetic TAV shows the smallest range with RSS reaching around 230Pa and the inclined textile TAV up to 280Pa. VSS limits were comparable among the 3 valves ranging between 5.2Pa and 5.7Pa. ConclusionHemodynamic similarities were found between the textile self-expandable valves and the bioprosthetic valve. This study constitutes another step towards showing the potential that textile valves have to become an alternative for the biological ones.

The hemodynamics of transcatheter aortic valves in transcatheter aortic valves

BackgroundThe durability of transcatheter aortic valves (TAVs) remains their greatest disadvantage, given that fixed tissue leaflets are not immune to structural degeneration from calcification and thrombosis. Therefore, a second intervention is necessary, especially given that TAV in low-risk patients has shown noninferior outcomes compared with surgery. This study aimed to assess the hemodynamic and turbulent properties of the flow downstream with different TAV-in-TAV configurations, to offer basic hemodynamic guidance for future interventions when currently implanted valves structurally degrade. MethodsSix TAV-in-TAV configurations were chosen: 23 mm Evolut-in-26 mm Evolut, 23 mm Evolut-in-23 mm SAPIEN 3, 26 mm Evolut-in-26 mm Evolut, 26 mm Evolut-in-23 mm SAPIEN 3, 23 mm SAPIEN3-in-26 mm Evolut, and 23 mm SAPIEN3-in-23 mm SAPIEN 3. Their hemodynamic performance was assessed in a pulse duplicator for 100 cycles. High-speed imaging and particle image velocimetry were performed to assess turbulence. Effective orifice area (EOA), pinwheeling index (PI), and Reynolds shear stress (RSS) were evaluated. ResultsThe largest mean EOA was obtained with 23 mm SAPIEN-in-26 mm Evolut (2.07 ± 0.06 cm2), and the smallest was obtained with 23 mm Evolut-in-23 mm SAPIEN (1.50 ± 0.04 cm2) (P < .001). The highest mean PI was obtained with SAPIEN-in-SAPIEN (26.5 ± 2.00%), and the lowest was obtained with 26 mm Evolut-in-26 mm Evolut (7.5 ± 1.6%) (P < .01). At peak systole, the least detrimental RSS range was obtained with 23 mm Evolut-in-26 mm Evolut (up to ∼340 Pa), and the most detrimental RSS range was obtained with 23 mm Evolut-in-SAPIEN (∼900 Pa) (P < .01). ConclusionsThis study shows that best hemodynamic parameters are TAV-specific (implanted and to be implanted). In addition, it shows that RSS levels, which are indicative of turbulence levels and associated with blood damage, are 2- to 3-fold higher after TAV-in-TAV.

Medium-term results of transcatheter implantation of MedLab-CT aortic valve prosthesis

Aim. To assess the clinical and hemodynamic results of transcatheter aortic valve replacement with the MedLab-CT prosthesis. Material and methods. MedLab-CT is the first Russian transcatheter implantable cardiac valve prosthesis. It is a balloon — an expandable stent, the cusps of which are made of 0,1 mm thick polytetrafluoroethylene plates. The use of synthetic material for the manufacture of the locking mechanism of the transcatheter implantable cardiac valve prostheses is a priority choice in the world. The reason was the hypothesis suggesting the absence of biodegradation of polytetrafluoroethylene in the body. The mechanical stability of the valve was tested on the pulse duplicator with a load equivalent to 10 years of functioning in the aortic position. The study included 69 patients who underwent implantation of the MedLab-CT prosthesis. One of the exclusion criteria for surviving patients was a follow-up period of less than 6 months. We estimated survival and incidence of clinically significant stroke, as well as hemodynamic parameters according to echocardiography for up to 3 years. Thirty nine patients were examined by face-toface approach, the rest ones underwent a telephone questionnaire survey. Results. The average follow-up was 9,6 months, the maximum — 3 years. Most patients belonged to the elderly group (average age 73,3 years). For 51 patients (74%) according to the EuroSCORE scale and for 37 (54%), according to the STS scale, a high risk of surgical intervention was determined: ≥8%.Mortality rate was 13% — 6 deaths were noted at the hospital stage, 3 patients died in the long term. No strokes recorded. In the face-to-face group, mean gradient on the aortic valve prosthesis was determined to be 8,41±4,21 mm Hg; insufficiency due to paraprosthetic fistulas not higher than I degree was observed in 7 patients (18%), not higher than II degree — in 1 patient; cases of transvalvular aortic insufficiency was not revealed. Conclusion. The results on the studied parameters are comparable with the data presented by foreign randomized clinical trials of imported models of transcatheter aortic valve prostheses.