Pulse Duplicator Research Articles

Influence of leaflet geometry on hydrodynamic performance of transcatheter aortic valve prostheses

Abstract The implantation of transcatheter aortic valve prostheses (TAVP) for therapy of aortic valve stenosis shows more and more clinically non-inferiority results compared to surgical valve replacement in intermediate and low risk patients. Commonly clinically used TAVP are manufactured from chemically fixed xenograft leaflet material, e.g. bovine or porcine pericardium. While the clinical use of TAVP currently extends, challenges concerning valve durability and leaflet calcification have to be addressed. In this regard, artificial leaflet materials represent a promising option for a next generation of TAVP. As a first step for the development of TAVP from polymeric nonwoven, the aim of this study was to determine the influence of leaflet geometry on hydrodynamic performance of TAVP prototypes. Based on a parametric model of the valve leaflets, we varied the curvature of the belly line forming the leaflet coaptation area from an initial, quite concave, leaflet geometry with a value of 0.5° to an almost straight geometry for the leaflets with a value 0.15°. Manufacturing of TAVP prototypes was conducted by means of electrospinning technique with a polycarbonate based silicone elastomer. Hydrodynamic characterization according to ISO 5840-3 standards was performed using a pulse duplicator system with a heart rate of 70 BPM, systolic duration of 35%, mean aortic pressure of 100 mmHg and a stroke volume of 96 ml. Cardiac output as well as mean transaortic pressure gradient, closing volume, leakage volume and regurgitation were measured to compare the different leaflet geometries. To summarize, the curvature of the leaflets’ belly has a crucial impact on TAVP hydrodynamics under physiological test conditions. In particular, the opening and closing behavior is strongly influenced by a steeper curvature leading to larger closing volumes and higher regurgitant fractions. Further studies are planned to identify an optimum with respect to leaflet material selection, leaflet geometry and hydrodynamic properties of TAVP.

Development of an in vitro test procedure for the characterization of left atrial appendage occluder devices

Abstract The implantation of an occluder in the left atrial appendage (LAA) is an emerging therapy for the treatment of patients suffering from atrial fibrillation and with a contraindication to oral anticoagulation. The LAA occluder (LAAO) provides a reduction of the potential risk of strokes by thromboembolism. Currently, only a few CE-approved devices are available on the market and the number of clinical trials is comparatively low. Furthermore, there is currently no standardized test method available for testing functionality of the occluder, especially for testing safe anchorage and permeability. Therefore, the aim of this study is to establish an in vitro test method to prove anchorage mechanism and permeability regarding thromboembolism of the LAAO under physiological conditions. A standardized technical and fully parameterized silicone model of a LAA, based on studies of different morphologies and sizes, was developed. The LAA model was mounted onto the left atrial chamber of a commercial pulse duplicator system to simulate physiological hemodynamic conditions. The test was performed using the Watchman device (Boston Scientific, USA; size: 31 mm). The inner implantation diameter of the LAA model was designed according to a target compression of 10% for the Watchman device in the implanted configuration. Furthermore, thrombus-like particles (n=150, d=1,7±0,05 mm) were added to represent the flushing of thrombi out of the LAA after device implantation. Within several cycles it was confirmed that no particles were washed out of the LAA model with the implanted occluder leading to a full protection against thromboembolism. It could also be shown that the occluder is firmly anchored in the LAA. Pressure measurements with sensors in the left atrium and in the LAA distal to the occluder could also show that the occluder has no influence on the pressure conditions in the LAA.

Pressure sensor emulator to improve longterm stability of heart valve testing systems

Abstract Fluid mechanical characterization of artificial heart valve prostheses requires reliable measurement of temperature, flow and pressure at normal heart rate. In vitro fatigue test procedures of artificial heart valve prostheses can take several months with up to 400 million cycles to assess valve performance and durability under simulated cardiac conditions at increased pulse frequency. In both cases, a minimum of user interventions for recalibration are required. In these tests, pressure data are collected for hydrodynamic heart valve characterization and for closed-loop control of pressure loading. In our study, the improvement of commercial heart valve testing systems (Vivitro Pulse Duplicator, Vivitro Labs Inc. and VDT-3600i, BDC Laboratories) is considered by substituting the built-in disposable pressure sensors (lifetime: one week) by longterm stable sensors. The selected highly accurate sensors (86A, TE Connectivity Corp.) provide amplified, linearized, calibrated and temperature compensated analog output signals. Their stainless steel construction allows for high media compatibility with corrosive liquids. Due to different sensitivity characteristics, these sensors are not fully compatible to the testing devices. To overcome this limitation, application-specific emulator interfaces were developed to connect the new sensors to the data acquisition part of the validated valve testing systems. To stay consistent with manufacturer’s device and software specification, we utilized fast analog signal conditioning, including scaling, offset calibration, out of range alarm and status indication. Compared to the originally equipped pressure sensors, emulator parameters, such as pressure range, precision, resolution and accuracy remained unchanged or even improved. For system verification the response characteristic, long-term stability and dynamic properties were examined in comparative studies

Fabrication of affordable pulse duplication system for the in-vitro cardiovascular experiments based on gear pump and orifice flowmeter

More than 18 millions of people are still suffering from cardiovascular diseases (CVD) globally. Although various hemodynamics features are known to be related to the development of the CVDs, scrutinizing all hemodynamic features in suffering patients is not technically feasible yet. Instead, in-vitro replications of physiological and pathological blood flows have been preferred to investigate the changes in hemodynamics. In this study, we manufactured affordable pulse duplication system for the in-vitro cardiovascular experiments. The instrument consists of gear pump, servo-motor, servo-driver, data acquisition modulus, reservoir and orifice, which costs less than 7000 $. The two pressure sensors are equipped on the orifice to measure the pulsatile flow rate based on the pressure drop. The flow rate is given to feedback system to exactly duplicate the desired flow waveform. The developed system was tested to replicate various aortic blood flow waveforms with 60 to 120 beat per minute, and the results showed that the pulse duplication system replicates the blood flow waveforms with an error of less than 0.4±0.4 L/min. The duplicated waveform was stable and changed less than 5 % after less than 40 feedback iterations.

In Vitro and Ex Vivo Hemodynamic Testing of an Innovative Occluder for Paravalvular Leak After Transcather Aortic Valve Implantation.

This study aims at achieving a proof-of-concept for a novel device designed to occlude the orifices that may form between transcatheter valves and host tissues after TAVI. The device effect on the performance of a SAPIEN XT with a paravalvular gap was assessed into an in vitro and ex vivo pulse duplicator. The in vitro tests were performed complying with the standard international regulations, measuring the trasvalvular pressure and regurgitant volumes with and without the paravalvular gap, and with the occluder correctly positioned into the gap. In the second series of tests, the leakage reduction due to the presence of the occluder was assessed for the same setup, into a beating swine heart. The occluder implantation decreased the regurgitant fraction of about 50% for the in vitro assessment and 75% for the ex vivo test, under rest operating conditions. These results suggest that suitably designed occluders can lead to important benefit in the PVL treatment.

Transcatheter aortic valve deployment influences neo-sinus thrombosis risk: An in vitro flow study.

We investigated the impact of (transcatheter heart valve) THV expansion at the level of the native annulus and implant depth on valve performance and neo-sinus flow stasis. Flow stasis in the neo-sinus is one of the identified risk factors of THV thrombosis. A 29 mm CoreValve and 26 mm SAPIEN 3 were deployed under different expansions (CoreValve, SAPIEN 3) and implant depths (CoreValve) within a patient-derived aortic root in a pulse duplicator. Fluorescent dye was injected during diastole into the neo-sinus and imaged over 20 cardiac cycles. Washout times were computed as a measure of flow stasis for each deployment. The 10% CoreValve under-expansion improved neo-sinus washout over full expansion by 8% (p < .001), and higher CoreValve implant depth improved neo-sinus washout (p < .001). The 10% SAPIEN 3 under-expansion improved neo-sinus washout by 23% (p < .001). Under-expansion of both valve types caused higher pressure gradients and smaller effective orifice areas than full expansion. Neo-sinus flow stasis is influenced by THV expansion and implant depth (CoreValve). The 10% valve under-deployment (oversizing) may facilitate reduced flow stasis in the neo-sinus with minimal increase in pressure gradients. This strategy may be helpful for patient anatomies, which are in-between transcatheter valve sizes.

Pulmonary versus aortic pressure behavior of a bovine pericardial valve

BackgroundThe Carpentier Edwards Perimount Magna Ease aortic valvular prosthesis (Edwards Lifesciences, Irvine, Calif) has been among the most frequently and successfully used tissue prosthetic cardiac valves. Furthermore, this prosthesis has been used off-label in the pulmonary position. Until now, there has been a paucity of data regarding the functioning of tissue prosthetic valves under pulmonary conditions. MethodsUsing a pulse duplicator, hydrodynamic characteristics of a 21-mm and 25-mm Magna Ease valve were evaluated. Among parameters evaluated were leakage orifice area, closing time (ie, time required to close), and leakage duration. This procedure was performed under different pulmonic pressure conditions (15/5 mm Hg, 28/11 mm Hg, 73/32 mm Hg) and normal aortic pressure (120/80 mm Hg) as a reference. Moving images were obtained using a Phantom MIRO M320S high-speed camera (Vision Research Inc, Wayne, NJ) at 600 frames per second and used to analyze valve area in closed position. ResultsUnder normal pulmonic conditions (28/11 mm Hg) the leakage orifice area was 0.020 ± 0.012 mm2 for the 21-mm valve and 0.054 ± 0.041 mm2 for the 25-mm valve (P = .03). Hydrodynamic characteristics of the valves differed between pulmonary and aortic testing condition. Valve closing volumes were significantly lower under pulmonary hypotension and normal pulmonary conditions than under normal aortic conditions (P < .05). ConclusionsUnder normal pulmonary pressure conditions, the hydrodynamic characteristics of Magna Ease valves are significantly different compared with aortic conditions. Further research is needed to determine whether these results are associated with prosthetic valve failure.

Bioinspired Heart Valve Prosthesis Made by Silicone Additive Manufacturing

Summary Synthetic implants made by traditional fabrication routes are not patient specific and rarely match the performance of their biological counterparts. We present an additive manufacturing approach for the digital fabrication of tissue-like aortic heart valves featuring customizable geometry and leaflet architectures that resemble those of native valve tissue. Using biocompatible silicones with tunable mechanical properties, heart valves were fabricated by combining spray and extrusion-based additive manufacturing processes. Computer simulations showed that bioinspired leaflet architectures strongly affect the stress distribution throughout the valves, minimizing stresses on the leaflet during a cardiac cycle. Our computational analysis was complemented by in vitro experiments in a pulse duplicator to demonstrate the outstanding hemodynamic performance of the printed heart valves under physiological pressure cycles. The ability to fabricate synthetic implants with tailored designs at multiple length scales is a key contribution toward the digital fabrication of functional implants that perform on par with native body parts.

Impact of Leaflet Laceration on Transcatheter Aortic Valve-in-Valve Washout: BASILICA to Solve Neosinus and Sinus Stasis

ObjectivesThe aim of this study was to evaluate any potential leaflet washout benefits after bioprosthetic or native aortic scallop intentional laceration to prevent iatrogenic coronary artery obstruction during TAVR (BASILICA) in transcatheter valve-in-valve (ViV) in the context of leaflet thrombosis. BackgroundLeaflet thrombosis after transcatheter aortic valve replacement is secondary to flow stasis in both the sinus and neosinus. Strategies to improve washout and ameliorate neosinus and sinus flow velocities may have the potential to mitigate the occurrence of clinical and subclinical leaflet thrombosis. MethodsA 23-mm Edwards SAPIEN 3 and a 26-mm Medtronic Evolut were deployed in a 23-mm transparent surgical aortic valve model before and after leaflet laceration. The valves were placed in the aortic position of a pulse duplicator flow loop. Particle image velocimetry was performed to quantify sinus flow hemodynamic status. A tracing fluorescent dye was injected to evaluate the number of cycles to washout in both regions of interest. ResultsThe leaflet laceration procedure led to an increase in the velocities in the sinus and the neosinus by 50% for Evolut ViV and 61.9% for SAPIEN 3 ViV. In addition, leaflet laceration led to a reduction in overall cycles to washout in the neosinus by at least 56% with the Evolut and 54.5% with the SAPIEN 3 and in the sinus by at least 16.7% with the Evolut and 60.8% with the SAPIEN. ConclusionsLeaflet laceration using a BASILICA-type approach may hold the potential to mitigate neosinus and sinus flow stasis. Controlled in vivo trials are necessary to establish the potential benefit of BASILICA to reduce the occurrence of leaflet thrombosis.

Impact of BASILICA on Sinus and Neo-Sinus Hemodynamics after Valve-in-Valve with and without Coronary Flow

Background/purposeThis study aims at evaluating the impact of BASILICA on neo-sinus and sinus hemodynamics with and without coronary flow. Leaflet thrombosis after valve-in-valve (ViV) may compromise not only leaflet mobility but also affect valve durability and performance. Methods/materialsIn a 23 mm transparent surgical aortic valve model, a 23 mm Edwards SAPIEN 3 and a 26 mm Medtronic Evolut were deployed before and after leaflet laceration, in models with and without coronary flow. Neo-sinus and sinus hemodynamics were evaluated in the aortic position of a pulse duplicator and particle image velocimetry was performed in order to quantify sinus flow hemodynamics along with sinus and neo-sinus washout. ResultsBASILICA-type leaflet laceration procedure led to (a) an increase in the velocities in the sinus and the neo-sinus by 50% for Evolut ViV with and without coronary flow, 70% for non-coronary SAPIEN 3 ViV and 10% for coronary SAPIEN 3 ViV, and (b) an improvement in overall washout up to 2 cycles in the neo-sinus and 0.5 cycles in the sinus. ConclusionsA BASILICA-type leaflet laceration approach may improve sinus and neo-sinus hemodynamics through decreasing flow stasis and enabling less confined blood flow. BASILICA confers coronary sinus flow patterns to the non-coronary sinus.

In-Vitro Pulsatile Flow Testing of Prosthetic Heart Valves: A Round-Robin Study by the ISO Cardiac Valves Working Group.

Hydrodynamic performance testing is one of the core in vitro assessments required by the ISO 5840 series of standards for all prosthetic heart valves. A round-robin study carried out in 2005 in accordance with ISO 5840:2005 revealed significant variabilities in prosthetic heart valve hydrodynamic performance measurements among the participating laboratories. In order to re-examine the inter-laboratory variability based on the "state-of-the-art" under ISO 5840-1 and 5840-2:2015, the ISO Cardiac Valve Working Groups decided in 2016 to repeat the round-robin study. A total of 13 international laboratories participated in the study. The test valves were chosen to be the St. Jude Medical Masters Series mechanical valves (19mm aortic, 25mm aortic, 25mm mitral, and 31mm mitral), which were circulated among the laboratories. The testing was conducted according to a common test run sequence, with prespecified flow conditions. The study revealed improved, yet still significant variability among different laboratories as compared to the 2005 study. The coefficient of variation ranged from 7.7 to 21.6% for the effective orifice area, from 10.1 to 32.8% for the total regurgitant fraction, and from 14.7 to 45.5% for the mean transvalvular pressure gradient. The study revealed the ambiguities in the current versions of the ISO 5840 series of standards and the shortcomings of some participating laboratories. This information has allowed the ISO Working Group to incorporate additional clarifying language into the ISO 5840-1, -2, and -3 standards that are currently under revision to improve in vitro assessments. The results presented here can also be used by the testing laboratories to benchmark pulse duplicator systems and to train and certify testing personnel.

Human cell-derived tissue-engineered heart valve with integrated Valsalva sinuses: towards native-like transcatheter pulmonary valve replacements

Transcatheter valve replacement indication is currently being extended to younger and lower-risk patients. However, transcatheter prostheses are still based on glutaraldehyde-fixed xenogeneic materials. Hence, they are prone to calcification and long-term structural degeneration, which are particularly accelerated in younger patients. Tissue-engineered heart valves based on decellularized in vitro grown tissue-engineered matrices (TEM) have been suggested as a valid alternative to currently used bioprostheses, showing good performance and remodeling capacity as transcatheter pulmonary valve replacement (TPVR) in sheep. Here, we first describe the in vitro development of human cell-derived TEM (hTEM) and their application as tissue-engineered sinus valves (hTESVs), endowed with Valsalva sinuses for TPVR. The hTEM and hTESVs were systematically characterized in vitro by histology, immunofluorescence, and biochemical analyses, before they were evaluated in a pulse duplicator system under physiological pulmonary pressure conditions. Thereafter, transapical delivery of hTESVs was tested for feasibility and safety in a translational sheep model, achieving good valve performance and early cellular infiltration. This study demonstrates the principal feasibility of clinically relevant hTEM to manufacture hTESVs for TPVR.

Tissue-engineered transcatheter vein valve

Chronic venous insufficiency affects over 2 million patients in the US alone, with severe cases involving thousands of patients with chronic leg ulcers and potential amputation. Current treatment options are limited, with surgical repair of vein valves being the most effective but challenging solution. A transcatheter vein valve made from a biologically-engineered matrix possessing the ability to regenerate has the potential to provide both valve function and long-term hemocompatibility and durability because the matrix becomes endothelialized and populated with host tissue cells. We have developed a novel tissue-engineered transcatheter vein valve (TEVV) on a Nitinol stent and demonstrated function and durability in vitro. Tissue was grown from fibroblasts in fibrin gel so as to embed the stent, with a tubular extension of the engineered tissue from one end of the stent that was stitched along opposite sides and everted into the stent to form a bileaflet valve. Following decellularization, to create an “off-the-shelf” TEVV comprised of the resulting collagenous matrix, it was tested in a pulse duplicator to evaluate hydrodynamic properties for a range of flow rates. The TEVV was shown to have forward pressure drops in the range of 2–4 mmHg, low closing volume, and nil regurgitation. Further hydrodynamic tests were performed after crimping and then again after 1 million cycle durability testing, showing no degradation of valve performance or any visual damage to the matrix. The TEVV held over 600 mmHg backpressure after the durability testing, ensuring the valve would withstand pressure spikes well outside of the normal in vivo range. Catheter-based delivery into the ovine iliac vein demonstrated TEVV closing 2 weeks p.o. and endothelialization without thrombosis 8 weeks p.o.

Search for an Optimal Design of a Bioprosthetic Venous Valve: In silico and in vitro Studies

Valve incompetence is a progressive disease of the venous system that may eventually lead to venous hypertension, pain, and ulcers. There is a need for a venous valve prosthesis to replace incompetent valves. Computational and experimental investigations on venous valve design and associated haemodynamics will undoubtedly advance prosthesis design and treatments. Here, the objective is to investigate the effect of venous valve on the fluid and solid mechanics. The hypothesis is that there exists a valve geometry that maximises leaflet shear stress (LSS) but minimises leaflet intramural stress (LIS; i.e., minimise stress ratio=LIS/LSS). To address the hypothesis, fully dynamic fluid-structure interaction (FSI) models were developed. The entire cycle of valve opening and closure was simulated. The flow validation experiments were conducted using a stented venous valve prosthesis and a pulse duplicator flow loop. Agreement between the output of FSI simulations and output of pulse duplicator was confirmed. The maximum flow rates were within 6% difference, and the total flow during the cycle was within 10% difference. The simulated high stress ratio region at the leaflet base (five times the leaflet average) predicted the disease location of the vast majority of explanted venous valves reported in clinical literature. The study found that the reduced valve height and leaflet dome shape resulted in optimal performance to provide the lowest stress ratio. This study proposes an effective design of venous prostheses and elaborates on the correlations of venous valve with clinical observations.

The influence of hematocrit on the hemodynamics of artificial heart valve using fluid-structure interaction analysis

Patients with severe aortic stenosis could regain the proper hemodynamic performance and cardiovascular output by restoring the diseased aortic valve with an artificial heart valve replacement. However, given the uniqueness of each patient, the hemodynamic improvements after an aortic valve replacement could vary. The biomechanical and hemodynamical parameters can be influenced by some major factors including the patient's blood pressure and hematocrit. Therefore, the objective of this study is to analyze the hemodynamics and valve mechanics of a bileaflet mechanical heart valve and investigate the hemorheological characteristics under the change of hematocrit. The fully coupled fluid-structure interaction (FSI) approach was used to model the hemodynamics and valve dynamics. Particle image velocimetry (PIV) experiments were conducted with in vitro benchtop model using ViVitro Pulse Duplicator to verify and validate the FSI models. The current numerical analysis revealed the hematocrit influenced the shear stress distributions over a cardiac cycle. The structural stresses in the mechanical valve were also affected by the distributions of the shear stress in the blood flow. Parameter dependencies found in the current study indicate that the hematocrit is influential when conducting patient-specific modelling of prosthetic heart valves.

Dynamic, patient-specific mitral valve modelling for planning transcatheter repairs.

Transcatheter, beating heart repair techniques for mitral valve regurgitation is a very active area of development. However, it is difficult to both simulate and predict the clinical outcomes of mitral repairs, owing to the complexity of mitral valve geometry and the influence of hemodynamics. We aim to produce a workflow for manufacturing dynamic patient-specific models to simulate the mitral valve for transcatheter repair applications. In this paper, we present technology and associated workflow, for using transesophageal echocardiography to generate dynamic physical replicas of patient valves. We validate our workflow using six patient datasets representing patients with unique or particularly challenging pathologies as selected by a cardiologist. The dynamic component of the models and their resultant potential as procedure planning tools is due to a dynamic pulse duplicator that permits the evaluation of the valve models experiencing realistic hemodynamics. Early results indicate the workflow has excellent anatomical accuracy and the ability to replicate regurgitation pathologies, as shown by colour Doppler ultrasound and anatomical measurements comparing patients and models. Analysis of all measurements successfully resulted in t critical two-tail > t stat and p values > 0.05, thus demonstrating no statistical difference between the patients and models, owing to high fidelity morphological replication. Due to the combination of a dynamic environment and patient-specific modelling, this workflow demonstrates a promising technology for simulating the complete morphology of mitral valves undergoing transcatheter repairs.

Evaluating the Performance of Cardiac Pulse Duplicators Through the Concept of Fidelity.

The advanced design techniques used in modern prosthetic heart valve (PHV) development require accurate replication of the entire cardiac cycle. While cardiac pulse duplicator (CPD) design has a direct impact on the PHV test data generated, no clear guidelines exist to evaluate the CPD's performance. In response to this, we present a method to quantitatively assess CPD performance. A method to establish the fidelity of CPDs was formulated based on the pressure/time relationship and the error related to this relationship's target. This method was applied to assess the performance of a custom-made CPD. The performance evaluation included the assessment of the motion control system and overall repeatability of pressure measurements using a St Jude Epic 21mm aortic valve. The CPD's motion control system had an average root mean square error (RMSE) beat-to-beat tracking accuracy of 0.046 ± 0.008mm. Assessment of the pressure measurements yielded a repeatability of < 2.4 ± 0.9mmHg RMSE beat-to-beat differential pressure. The combination of pressure and its location within a heartbeat (fidelity) was within 5.0% of the individual targets for at least 95% of heartbeats. Fidelity can be used to objectively quantify the performance of various aspects of CPDs and to identify the cause of unexpected PHV or CPD behaviour. It also enables comparisons to be made among various CPDs in terms of overall performance. This approach may enable standardization of the assessment of CPD performance in the future.

Modeling of the Instantaneous Transvalvular Pressure Gradient in Aortic Stenosis.

The simplified and modified Bernoulli equations break down in estimating the true pressure gradient across the stenotic aortic valve due to their over simplifying assumptions of steady and inviscid conditions as well as the fundamental nature in which aortic valves are different than idealized orifices. Nevertheless, despite having newer models based on time-dependent momentum balance across an orifice, the simplified and modified Bernoulli continue to be the clinical standard because to date, they remain the only models clinically implementable. The objective of this study is to (1) illustrate the fundamental considerations necessary to accurately model the time-dependent instantaneous pressure gradient across a fixed orifice and (2) propose empirical corrections when applying orifice based models to severely stenotic aortic valves. We introduce a general model to predict the time-dependent instantaneous pressure gradient across an orifice that explicitly model the Reynolds number dependence of both the steady and unsteady terms. The accuracy of this general model is assessed with respect to previous models through pulse duplicator experiments on a round orifice model as well as an explanted stenotic surgical aortic valve both with geometric areas of 0.6cm2 (less than 1cm2 which is the threshold for stenosis determination) over cardiac outputs of 3 and 5L/min and heart rates of 60, 90 and 120bpm. The model and the raw experimental data corresponding to the orifice showed good agreement over a wide range of cardiac outputs and heart rates (R2 exceeding 0.91). The derived average and peak transvalvular pressure gradients also demonstrated good agreement with no significant differences between the respective peaks (p > 0.09). The new model proposed holds promise with its physical and closed form representation of pressure drop, however accurate modeling of the time-variability of the valve area is necessary for the model to be applied on stenotic valves.

A case study on implantation strategies to mitigate coronary obstruction in a patient receiving transcatheter aortic valve replacement

Coronary obstruction is a life threatening complication during and post-transcatheter aortic valve replacement (TAVR). The objective of this preliminary work is to investigate the mechanisms underlying coronary obstruction in a patient after TAVR, in whom coronary obstruction was confirmed in addition to highlighting the importance of pre-procedural planning. The aortic root of an 80-year old male patient with coronary obstruction during TAVR–where a 29 mm SAPIEN 3 was deployed-was segmented from Computed Tomography scans and 3D-printed with compliant material. Flow and pressure data were acquired in this 3D-printed model in-vitro using a pulse duplicator under physiological conditions for the cases: a 29 mm SAPIEN 3, a 26 mm SAPIEN 3 expanded with a 29 mm balloon, and a 31 mm Medtronic-CoreValve deployed annularly, supra and sub-annularly respectively. Only the CoreValve in sub-annular axial position and the 29 mm SAPIEN 3 yielded pressure gradients (PG) lower than 10 mmHg (6.76 ± 0.52 and 5.72 ± 0.13 mmHg respectively) while the 26 mm SAPIEN 3, CoreValve in normal and supra-annular positions yielded higher PGs (15.5 ± 0.48, 12.2 ± 0.15 and 10.8 ± 0.24 mmHg respectively). 29 mm SAPIEN 3 implantation yielded an FFR value of 45.7 ± 0.6%. However, 31 mm CoreValve in any of the three different annular positions yielded FFR values going from 89.6 ± 1.1% in supra-annular position to 98.3 ± 1.1% in sub-annular position. Implantation with a 26 mm SAPIEN 3 expanded with a 29 mm balloon also yielded an FFR of 92.1 ± 1.2%. Coronary obstruction in this patient could have been prevented through usage of different valve types and/or through usage of a different combination of valve size-balloon sizes.

The Effect of Ventricular Compliance on Pulse Duplicator Test Results

The Effect of Ventricular Compliance on Pulse Duplicator Test Results