A Novel Transcatheter Device for the Edge-to-Edge Treatment of Tricuspid Regurgitation: A Preliminary Evaluation.

Tricuspid regurgitation (TR) is the most common pathology of the tricuspid valve (TV), with significant mortality in severe cases. A well-established strategy to treat TR is represented by the clover surgical technique, which consists of stitching together the free edges of TV leaflets, producing a clover-shaped valvular orifice. Transcatheter treatments for TR constitute a valuable alternative for high-risk patients. In this work we investigated haemodynamic performances and safety of a novel device (StarTric device (STD)) aiming to perform the clover technique via percutaneous access. To assess haemodynamic performances, STD and clover were applied on porcine pathological TVs and tested. Fluid dynamic indexes of both strategies were compared to the pathological model. To evaluate device safety, forces exchanged between device and leaflets were compared to the extraction force (EF) required to STD to completely pass through the leaflet. Clover technique and STD induced a comparable TV backflow reduction (48% and 47%, respectively), with associated increase of TV flow in all tested conditions. Diastolic transvalvular pressure similarly increased indicating a reduction, though not significant, of the valvular orifice. Forces ranged from 1N to 1.71N, compared to an EF of 22.16 ± 8.6N. Force varied significantly amongst different working conditions (normotensive, mild, and severe hypertensive) for each leaflet, whilst no significative variation was found on different leaflets in the same working condition. In the adopted experimental scenario, STD demonstrated comparable efficacy to the surgical strategy in restoring TV haemodynamic. The forces acting on the leaflets following STD implantation were far lower when compared to EFs.

Coronary Perfusion After Valve-in-Valve Transcatheter Aortic Valve Implantation in Small Aortic Root: In Vitro Experimental Assessment.

Coronary flow obstruction following transcatheter aortic valve-in-valve implantation (VIV-TAVI) is associated with a high mortality risk. The aim of this work was to quantify the coronary perfusion after VIV-TAVI in a high-risk aortic root anatomy. 3D printed models of small aortic root were used to simulate the implantation of a TAVI prosthesis (Portico 23) into surgical prostheses (Trifecta 19 and 21). The aortic root models were tested in a pulsatile in vitro bench setup with a coronary perfusion simulator. The tests were performed at baseline and post-VIV-TAVI procedure in aligned and misaligned commissural configurations under simulated hemodynamic rest and exercise conditions. The experimental design provided highly controllable and repeatable flow and pressure conditions. The left and right coronary mean flow did not differ significantly at pre- and post-VIV-TAVI procedure in any tested configurations. The commissural misalignment did not induce any significant alterations to the coronary flow. High-risk aortic root anatomy did not trigger coronary ostia obstruction or coronary flow alteration after transcatheter aortic valve implantation in a surgical bioprosthesis as shown from in-vitro flow loop tests.

Morphometric Characterization of an Ex Vivo Porcine Model of Functional Tricuspid Regurgitation.

Emerging treatments for tricuspid valve (TV) regurgitation require realistic TV pathological models for preclinical testing. The aim of this work was to investigate structural features of fresh and defrosted porcine right-heart samples as models of mild and severe functional tricuspid regurgitation (FTR) condition in ex-vivo pulsatile flow platform. Ten fresh hearts were tested ex-vivo under steady and pulsatile flow in typical right-heart loading conditions. Hemodynamics and 3D echocardiographic imaging of TV and right ventricle (RV) were acquired. Hearts were then kept frozen for 14 days, defrosted, and tested again with the same protocol. Morphometric parameters of TV and RV were derived from 3D reconstructions based on echo data. Fresh samples showed a slightly dilated TV morphology, with coaptation gaps among the leaflets. Sample freezing induced worsening of TV insufficiency, with significant (p < 0.05) increases in annulus size (annulus area and perimeter 7.7-3.1% respectively) and dilation of RV (9.5%), which led to an increase in tenting volume (123.7%). These morphologic alterations reflected into a significant increment of regurgitation fraction (27%). Together, such results suggest that fresh porcine heart samples may be a reliable ex-vivo model of mild FTR condition, which can be enhanced through freezing/thawing treatment to model a severe pathological condition.

Development and Validation of a Novel Skills Training Model for PCNL, an ESUT project.

BACKGROUND AND AIM: The aim of this study is to validate a totally non biologic training model that combines the use of ultrasound and X ray to train Urologists and Residents in Urology in PerCutaneous NephroLithotripsy (PCNL). METHODS: The training pathway was divided into three modules: Module 1, related to the acquisition of basic UltraSound (US) skill on the kidney; Module 2, consisting of correct Nephrostomy placement; and Module 3, in which a complete PCNL was performed on the model. Trainees practiced on the model first on Module 1, than in 2 and in 3. The pathway was repeated at least three times. Afterward, they rated the performance of the model and the improvement gained using a global rating score questionnaire. RESULTS: A total of 150 Urologists took part in this study. Questionnaire outcomes on this training model showed a mean 4.21 (range 1-5) of positive outcome overall. Individual constructive validity showed statistical significance between the first and the last time that trainees practiced on the PCNL model among the three different modules. Statistical significance was also found between residents, fellows and experts scores. Trainees increased their skills during the training modules. CONCLUSION: This PCNL training model allows for the acquisition of technical knowledge and skills as US basic skill, Nephrostomy placement and entire PCNL procedure. Its structured use could allow a better and safer training pathway to increase the skill in performing a PCNL.

In vitro four-dimensional flow magnetic resonance analysis of the effect of pericardial valve design on aortic flow.

We investigated the effect of the design of bioprosthetic pericardial valves on the downstream fluid flow pattern through four-dimensional flow magnetic resonance imaging (4D Flow). A dedicated in vitro test bench, including a paradigmatic aortic root phantom, was used to compare, under steady flow conditions, three commercially used pericardial bioprostheses (TrifectaTM, Carpentier-Edwards PERIMOUNT Magna, Crown PRT®), selecting the two smallest and comparable valve sizes. In-house 4D Flow post-processing provided the downstream flow pattern of velocity, the velocity profile at vena contracta, its effective orifice area (EOA) and the corresponding hydraulic diameter (DH). Trifecta reported the lowest peak of velocity for both the tested sizes, with vena contracta position being the most proximal to the free margin of leaflets. Conversely, in both Crown and Magna, jet flow continued to increase its downstream velocity, resulting in a farther position of vena contracta. EOA shape was trilobal for Magna, triangular for Crown and circular for Trifecta, the last one maximising EOA. The percentage of nominal luminal area effectively exploited by the flow was largely above 80% in Trifecta, below 75% in Crown and below 70% in Magna. Hence, the design of pericardial bioprostheses directly impacts on the downstream flow field pattern and its fluid dynamic performance.

Commissural repositioning in bicuspid aortic valve repair: an in vitro acute model to explore and explain different results.

OBJECTIVES: Commissural orientation <160° is a recognized risk factor for bicuspid aortic valve repair failure. Based on this observation, repairing this subtype of aortic valve by reorienting the 2 commissures at 180° has recently been proposed. METHODS: Nine porcine hearts with aortic annulus diameters of 25 mm were selected. A pathological model of a Sievers 1 bicuspid aortic valve was obtained by suturing the coaptation line between the left and right leaflets. Each heart underwent reimplantation procedures both in the native (120°) and the reoriented (180°) configuration. After the operation, each sample was tested on a pulse duplicator at rest (heart rate 60 beats per min) and with mild exercise (heart rate 90 beats per min) conditions. RESULTS: No statistically significant difference was noted in mean and peak transvalvular aortic gradients between the 2 configurations at rest (18.6 ± 5 vs 17.5 ± 4 for the mean aortic gradient; 42.8 ± 12.7 vs 36.3 ± 5.8 for the peak aortic gradient) but the group with the 120°-oriented commissures had significantly higher mean transaortic gradients compared to the group with the 180°-oriented commissures at initial exercise stress conditions (30.1 ± 9.1 vs 24.9 ± 3.8; p value 0.002). CONCLUSIONS: The 180° commissural reorientation of the asymmetrical bicuspid aortic valve does not improve the transvalvular aortic gradient in an acute model at rest conditions, but it could do so under stress situations. Even if it is surgically more complex and time-consuming, this approach could be a good strategy to improve long-term results, particularly in young patients.

Ex Vivo Model of Functional Mitral Regurgitation Using Deer Hearts.

Transcatheter therapies are emerging for functional mitral regurgitation (FMR) treatment, however there is lack of pathological models for their preclinical assessment. We investigated the applicability of deer hearts for this purpose.8 whole deer hearts were housed in a pulsatile flow bench. At baseline, all mitral valves featured normal coaptation. The pathological state was induced by 60-minutes intraventricular constant pressurization. It caused mitral annulus dilation (antero-posterior diameter increase from 31.8 ± 5.6 mm to 39.5 ± 4.9 mm, p = 0.001), leaflets tethering (maximal tenting height increase from 7.3 ± 2.5 mm to 12.7 ± 3.4 mm, p < 0.001) and left ventricular diameter increase (from 67.8 ± 7.5 mm to 79.4 ± 6.5 mm, p = 0.004). These geometrical reconfigurations led to restricted mitral valve leaflets motion and leaflet coaptation loss. Preliminary feasibility assessment of two FMR treatments was performed in the developed model.Deer hearts showed ability to dilate under constant pressurization and have potential to be used for realistic preclinical research of novel FMR therapies. Graphical abstract figure legend: Deer heart mitral valve fiberscopic and echocardiographic images in peak systole at baseline and after inducing the pathological conditions representing functional mitral regurgitation. In the pathological conditions lack of coaptation between the leaflets, enlargement of the antero-posterior distance (red dashed line) and the left ventricular diameter (orange dashed line) were observed.

Leaflet kinematics after the Yacoub and Florida-sleeve operations: results of an in vitro study.

OBJECTIVES: The Florida-sleeve is a valve-sparing technique that causes minimal interference to leaflet kinematics and aortic root dynamism. The aim of this in vitro study was to evaluate the effects of the Florida-sleeve and Yacoub techniques on aortic leaflet kinematics. METHODS: Two groups of 6 whole porcine hearts were treated with either the Florida-sleeve technique or the Yacoub technique and tested in a pulsatile loop. Valve fluid dynamics, coronary flow analysis and valve echocardiograms were performed both before and after the procedures. RESULTS: Both procedures showed no difference in rapid valve opening time as compared with their respective baseline values. The Florida-sleeve procedure showed a shorter slow closing time (192 ± 19 ms vs baseline 244 ± 14 ms, P = 0.016) and increased slow closing velocity (-1.5 ± 0.4 cm/s vs baseline -0.8 ± 0.4 cm/s, P = 0.038). In the rapid valve closing phase, the Yacoub procedure showed a trend towards slower closing valve velocity (-16 ± 9 cm/s vs baseline -25 ± 9 cm/s, P = 0.07). The Yacoub procedure showed larger leaflet displacement at the end of the slow valve closing time that was 2.0 ± 0.5 cm vs baseline 1.5 ± 0.3 cm, P = 0.044. When comparing the Florida-sleeve and Yacoub procedures, the former showed statistically significant shorter slow valve closing time (P = 0.017). CONCLUSIONS: This study showed that the Florida-sleeve technique alters the slow closing phase of the aortic valve leaflet kinematics when compared with both the normal baseline and Yacoub procedure, while the latter showed a larger leaflet displacement before the rapid closing valve phase.

4D Flow MRI hemodynamic benchmarking of surgical bioprosthetic valves.

PURPOSE: We exploited 4-dimensional flow magnetic resonance imaging (4D Flow), combined with a standardized in vitro setting, to establish a comprehensive benchmark for the systematic hemodynamic comparison of surgical aortic bioprosthetic valves (BPVs). MATERIALS AND METHODS: 4D Flow analysis was performed on two small sizes of three commercialized pericardial BPVs (Trifecta™ GT, Carpentier-Edwards PERIMOUNT Magna and Crown PRT®). Each BPV was tested over a clinically pertinent range of continuous flow rates within an in vitro MRI-compatible system, equipped with pressure transducers. In-house 4D Flow post-processing of the post-valvular velocity field included the quantification of BPV effective orifice area (EOA), transvalvular pressure gradients (TPG), kinetic energy and viscous energy dissipation. RESULTS: The 4D Flow technique effectively captured the 3-dimensional flow pattern of each device. Trifecta exhibited the lowest range of velocity and kinetic energy, maximized EOA (p < 0.0001) and minimized TPGs (p ≤ 0.015) if compared with Magna and Crown, these reporting minor EOA difference s (p ≥ 0.042) and similar TPGs (p ≥ 0.25). 4D Flow TPGs estimations strongly correlated against ground-truth data from pressure transducers; viscous energy dissipation proved to be inversely proportional to the fluid jet penetration. CONCLUSION: The proposed 4D Flow analysis pinpointed consistent hemodynamic differences among BPVs, highlighting the not negligible effect of device size on the fluidynamic outcomes. The efficacy of non-invasive 4D Flow MRI protocol could shed light on how standardize the comparison among devices in relation to their actual hemodynamic performances and improve current criteria for their selection.

Effect of the valve design on pressure drop, pressure recovery, and spatial positioning of vena contracta.

BACKGROUND: Bioprostheses are complex structures and yield a very complex fluid dynamics. Hence, it can be hypothesized that prosthesis structural characteristics affect the position of the vena contracta and, consequently, influences the pattern and the extent of pressure recovery downstream from the vena contracta. MATERIALS AND METHODS: The study was performed on pericardial aortic prostheses, specifically Crown 21 and 23 (LivaNova PLC, UK), Trifecta 19 and 21 (Edwards Lifescience, USA), and Magna 19 and 21(Abbott, USA), tested in an "ad hoc" devised steady flow loop circuit at four flow rates (10, 15, 20, and 25 L/min). Fluid dynamic quantities were obtained by direct pressure measurement and Doppler interrogation. RESULTS: Pressure drop at 25 L/min flow rate was 26.5 ± 0.3 mm Hg and 14.9 ± 0.1 mm Hg for the Trifecta 19 and 21, 37.1 ± 1.0 mm Hg and 27.3 ± 0.4 mm Hg for the Magna 19 and 21, and 36.6 ± 1.0 mm Hg and 22.7 ± 0.1 mm Hg for Crown 21 and 23, respectively. The vena contracta was shorter for Trifecta compared with the Magna and the Crown in which it developed further downstream and as far as 1 cm from the valve leaflets fringes. The pressure recovery was 54% ± 1% for Trifecta 21, 39% ± 1% for Magna 21, and 41% ± 2% for Crown 23 with different patterns. CONCLUSION: The design of bioprosthesis affects pressure recovery and the position of the vena contracta. The different patterns of pressure recovery might have clinical impact.

Fluid-Structure Interaction and In Vitro Analysis of a Real Bileaflet Mitral Prosthetic Valve to Gain Insight Into Doppler-Silent Thrombosis.

Prosthetic valve thrombosis (PVT) is a serious complication affecting prosthetic heart valves. The transvalvular mean pressure gradient (MPG) derived by Doppler echocardiography is a crucial index to diagnose PVT but may result in false negatives mainly in case of bileaflet mechanical valves (BMVs) in mitral position. This may happen because MPG estimation relies on simplifying assumptions on the transvalvular fluid dynamics or because Doppler examination is manual and operator dependent. A deeper understanding of these issues may allow for improving PVT diagnosis and management. To this aim, we used in vitro and fluid-structure interaction (FSI) modeling to simulate the function of a real mitral BMV in different configurations: normally functioning and stenotic with symmetric and completely asymmetric leaflet opening, respectively. In each condition, the MPG was measured in vitro, computed directly from FSI simulations and derived from the corresponding velocity field through a Doppler-like postprocessing approach. Following verification versus in vitro data, MPG computational data were analyzed to test their dependency on the severity of fluid-dynamic derangements and on the measurement site. Computed MPG clearly discriminated between normally functioning and stenotic configurations. They did not depend markedly on the site of measurement, yet differences below 3 mmHg were found between MPG values at the central and lateral orifices of the BMV. This evidence suggests a mild uncertainty of the Doppler-based evaluation of the MPG due to probe positioning, which yet may lead to false negatives when analyzing subjects with almost normal MPG.

Experimental quantification of the fluid dynamics in blood-processing devices through 4D-flow imaging: A pilot study on a real oxygenator/heat-exchanger module.

The performance of blood-processing devices largely depends on the associated fluid dynamics, which hence represents a key aspect in their design and optimization. To this aim, two approaches are currently adopted: computational fluid-dynamics, which yields highly resolved three-dimensional data but relies on simplifying assumptions, and in vitro experiments, which typically involve the direct video-acquisition of the flow field and provide 2D data only. We propose a novel method that exploits space- and time-resolved magnetic resonance imaging (4D-flow) to quantify the complex 3D flow field in blood-processing devices and to overcome these limitations. We tested our method on a real device that integrates an oxygenator and a heat exchanger. A dedicated mock loop was implemented, and novel 4D-flow sequences with sub-millimetric spatial resolution and region-dependent velocity encodings were defined. Automated in house software was developed to quantify the complex 3D flow field within the different regions of the device: region-dependent flow rates, pressure drops, paths of the working fluid and wall shear stresses were computed. Our analysis highlighted the effects of fine geometrical features of the device on the local fluid-dynamics, which would be unlikely observed by current in vitro approaches. Also, the effects of non-idealities on the flow field distribution were captured, thanks to the absence of the simplifying assumptions that typically characterize numerical models. To the best of our knowledge, our approach is the first of its kind and could be extended to the analysis of a broad range of clinically relevant devices.

Hydrodynamic and Geometric Behavior of Two Pericardial Prostheses Implanted in Small Aortic Roots.

Hydrodynamic performance of stented bioprostheses is far below that of the native valve. One of the reasons is that the internal diameter of the prosthesis is usually smaller than that of the native valve. However, other valve characteristics are also important in generating the pressure drop. We aimed to assess, in an ex vivo pulsatile mock loop, the hydrodynamic behavior of two bioprostheses, Trifecta and Mitroflow, to ascertain which geometric terms are limiting factors in hydrodynamic performance. At stroke volumes between 30 and 60 ml, Trifecta showed lower pressure drop, energy dissipation and valve resistance, and greater effective orifice area. This trend was overturned at higher stroke volumes, with Mitroflow slightly outperforming Trifecta. The geometric determinants were consistent with these results. Trifecta achieved its maximum opening area already at the lowest stroke volumes, featuring a divergent shape at the systolic peak. Mitroflow showed a complex opening pattern, featuring a convergent shape at the systolic peak for lower stroke volumes, while reaching its maximum opening area at higher stroke volumes, with a divergent shape. The two bioprostheses, although similar in design, displayed different biomechanical behaviors. The internal diameter of each bioprosthesis did not show to be strictly correlated with its hydrodynamic characteristics.

Opening/closing pattern of Trifecta and Freestyle valves versus native aortic valve: Are stentless valves more physiologic than a stented valve?

BACKGROUND: Stentless valves have long been considered the ideal valves in terms of hemodynamics. Recently, the Trifecta valve, a stented bioprosthesis with excellent fluid dynamic characteristics, has become available. The aim of the study was to compare the opening/closing pattern of the Freestyle stentless valve and the Trifecta valve with that of the native aortic valve. METHODS: A total of 12 patients with a Freestyle and 10 with a Trifecta valve were compared to normal native aortic valves in 12 control patients. Leaflet kinematics and hemodynamic parameters were obtained by echocardiographic M-mode and Doppler measurements. RESULTS: The control group displayed significantly longer Rapid Valve Opening Time (45 ± 7 ms) and Rapid Valve Closing Time (42 ± 9 ms) than Freestyle patients (Rapid Valve Opening Time: 32 ± 7 ms; Rapid Valve Closing Time: 31 ± 8 ms) and Trifecta patients (Rapid Valve Opening Time: 31 ± 7 ms; Rapid Valve Closing Time: 30 ± 8 ms) (P < 0.0001). The maximal leaflet displacement reached at the end of rapid valve opening was 16.7 ± 3.2 mm, 17.7 ± 2.3 mm, and 17.7 ± 5.3 mm (P = 0.42) in the Freestyle, Trifecta, and control groups, respectively. The total opening time was shorter in the control group (223 ± 25 ms) than in Freestyle (319 ± 61 ms) and Trifecta (324 ± 46 ms) patients (P < 0.0001). CONCLUSIONS: The Freestyle stentless valve was not superior to the Trifecta valve in terms of kinematics and functions more like a stented bioprosthesis.

MitraClip removal: surgical techniques to preserve native mitral valve leaflets.

Transcatheter valve procedures are wide-spreading techniques for the treatment of heart valves pathologies. In case of implantation failure, the transcatheter device often needs to be removed. This procedure, which can alter the biological structure integrity, can limit the option available for the subsequent traditional surgery. One of the most popular devices for transcatheter mitral valve repair is the MitraClip system. In this work, we describe 2 different techniques for the surgical removal of MitraClip. These techniques aim to preserve the valve leaflets integrity, to allow for subsequent mitral valve surgical repair.

Modelling of Lesions Associated with Functional Mitral Regurgitation in an Ex Vivo Platform.

Functional mitral regurgitation (FMR) is a complex pathology involving valvular and subvalvular structures reconfiguration, and its treatment is considered challenging. There is a lack of experimental models allowing for reliable preclinical FMR treatments' evaluation in a realistic setting. A novel approach to simulate FMR was developed and incorporated into an ex vivo passive beating heart platform. FMR was obtained by dilating the mitral annulus (MA) mainly in the antero-posterior direction and displacing the papillary muscles (PMs) apically and laterally by ad hoc designed and 3D printed dilation and displacing devices. It caused hemodynamic and valve morphology alterations. Isolated MA dilation (MAD) led to significantly increased antero-posterior distance (A-P) and decreased coaptation height (CH), tenting area (TA) and systolic leaflets angulation, resembling clinically recognized type I of mitral regurgitation with normal leaflet motion. Whereas concomitant MAD with PM displacement caused an increase in A-P, TA, CH. This geometrical configuration replicated typical determinants of type IIIb lesion with restricted leaflet motion. The proposed methods provided a realistic and repeatable ex vivo FMR model featuring two lesions clinically associated with the pathology. It bears a promise to be successfully utilized in preclinical studies, clinical training and medical education.

A novel system for the treatment of aortic annular dilation: an ex vivo investigation.

OBJECTIVES: The main reason for aortic repair failures is recurrent annular dilatation. The fibrous portion of left ventricular outflow tract dilates. A novel device was designed to tackle this problem. METHODS: The device consists of an internal ring applied at the aortic annulus plus an external flexible band at the level of the aortic root. The internal ring has a semi-rigid portion (40%, placed at ventriculo-arterial junction) and a flexible portion to allow it to conform along the curves of the non-coronary/right coronary leaflet and right coronary/left coronary leaflet commissures. The external band acts as a reinforcement to the internal ring. A pulsatile mock loop capable of housing porcine aortic valve was used. Working conditions were 60 bpm of heart rate, 75 of stroke volumes and 120-80 mmHg of simulated pressure. Mean gradient, effective orifice area, annular diameter, coaptation height and length were recorded on 11 aortic root units (ARUs). High-speed video and standard echocardiographic images were also recorded. All data were acquired in the following conditions: (i) basal (untreated ARU); (ii) pathological condition (left coronary/non-coronary triangle was dilated by suturing an aortic patch); and (iii) ARU treated with the device. RESULTS: Gradients and effective orifice area were respectively 0.9 ± 0.64 mmHg and 3.1 ± 0.7cm2 (pathological) and 3.7 ± 1.1 mmHg and 1.5 ± 0.2cm2 (treated, P < 0.05). Left coronary/non-coronary diameter decreased from 2.4 ± 0.2 cm (pathological) to 2.0 ± 0.2 (treated, P < 0.05). Coaptation length and height were fully restored to basal values following treatment. Visual inspection showed proper dynamics of the leaflet, confirmed by high-speed video and echocardiography. CONCLUSIONS: The device allowed for restoring physiologic-like coaptation in the experimental model, without inducing clinically relevant worsening of the haemodynamics of the treated ARU.

Functional Tricuspid Regurgitation Model in a Beating Heart Platform.

Currently, clinicians are seeking new, minimally invasive treatment options for functional tricuspid regurgitation (FTR). Challenging tricuspid complexity requires the evaluation of the treatment techniques in adequate and realistic preclinical scenario. The purpose of this article is to describe the design and functional assessment of a novel passive beating heart model of the pulmonary circulation with the possibility to tightly control FTR. The model housed porcine hearts actuated by a volumetric pump that cyclically pressurized the right ventricle. The in-vitro FTR model exploited the tendency of the ventricle to dilate under pressure. The dilation entailed papillary muscles displacement and valve annulus enlargement, thus inducing tricuspid valve insufficiency. Employment of constraint bands allowed to restore valve competency. The system provided consistent replication of the main determinants of the pulmonary hemodynamics in a wide range of working conditions. The experimental model of FTR was reliable, easily controllable, and showed good stability-over-time. Echocardiography and fiberscope imaging provided a unique opportunity to investigate valve dynamics. These features make the platform suitable for realistic training purposes and testing of the upcoming FTR therapies.

Comparison of the Performance of a Sutureless Bioprosthesis With Two Pericardial Stented Valves on Small Annuli: An In Vitro Study.

BACKGROUND: Aortic valve replacement has evolved recently with the development of the sutureless bioprosthesis. One such valve is the Perceval bioprosthesis, which is built by mounting leaflets of bovine pericardium to a thin stent; this approach has the potential to provide an excellent fluid dynamic performance. We undertook an in vitro study to compare the hydrodynamic performance of the sutureless bioprosthesis with two standard pericardial stented bioprostheses (Crown and Magna). METHODS: Tests were conducted using a mock loop, testing on two sizes of the three prostheses. The prosthesis sizes were chosen to house the valves in porcine aortic roots with a native annulus diameter of 19 mm (n = 6) or 21 mm (n = 6). The stroke volume ranged from 25 mL to 105 mL at a simulated heart rate of 70 beats per minute. RESULTS: Mean pressure drop and energy loss rose with increasing stroke volume in all of the valves tested (p < 0.001), with the sutureless valve showing the lowest values for both variables (p < 0.001). Effective orifice area values were stable across the stroke volume intervals and were larger in the sutureless valves (p < 0.001). CONCLUSIONS: All of the valves tested provided good fluid dynamic performances. The sutureless bioprosthesis provided the best performance with the least hindrance to flow behavior. From the hydrodynamic perspective, the sutureless prosthesis may present an advance in the evolution of bioprostheses, ensuring low gradients and potential for low incidence of patient-prosthesis mismatch even in small annuli.

Full Mimicking of Coronary Hemodynamics for Ex-Vivo Stimulation of Human Saphenous Veins.

After coronary artery bypass grafting, structural modifications of the saphenous vein wall lead to lumen narrowing in response to the altered hemodynamic conditions. Here we present the design of a novel ex vivo culture system conceived for mimicking central coronary artery hemodynamics, and we report the results of biomechanical stimulation experiments using human saphenous vein samples. The novel pulsatile system used an aortic-like pressure for forcing a time-dependent coronary-like resistance to obtain the corresponding coronary-like flow rate. The obtained pulsatile pressures and flow rates (diastolic/systolic: 80/120 mmHg and 200/100 mL/min, respectively) showed a reliable mimicking of the complex coronary hemodynamic environment. Saphenous vein segments from patients undergoing coronary artery bypass grafting (n = 12) were subjected to stimulation in our bioreactor with coronary pulsatile pressure/flow patterns or with venous-like perfusion. After 7-day stimulation, SVs were fixed and stained for morphometric evaluation and immunofluorescence. Results were compared with untreated segments of the same veins. Morphometric and immunofluorescence analysis revealed that 7 days of pulsatile stimulation: (i) did not affect integrity of the vessel wall and lumen perimeter, (ii) significantly decreased both intima and media thickness, (iii) led to partial endothelial denudation, and (iv) induced apoptosis in the vessel wall. These data are consistent with the early vessel remodeling events involved in venous bypass adaptation to arterial flow/pressure patterns. The pulsatile system proved to be a suitable device to identify ex vivo mechanical cues leading to graft adaptation.