A percutaneous approach to create tricuspid regurgitation in swine: a model for transcatheter tricuspid valve therapy assessment.

PURPOSE: The purpose of this study was to develop a simple and effective percutaneous approach to create tricuspid regurgitation in swine. METHODS: Eleven pigs (71.68 ± 7.70 kg, 3 male) were involved in this study. A grasping forceps was introduced into the right ventricle through a steerable sheath under fluoroscopic guidance and used to disrupt the tricuspid valve apparatus by avulsing leaflet or chordae tendineae repeatedly. Transthoracic echocardiography and right ventricular angiography were used to evaluate the degree of tricuspid regurgitation created. RESULTS: Ten of the 11 pigs (90.91%) achieved severe tricuspid regurgitation and 1 (9.09%) obtained moderate tricuspid regurgitation immediately after the procedure. Heart rate of the pigs significantly increased immediately after tricuspid regurgitation creation compared to baseline (88.64 ± 23.24 vs. 76.00 ± 15.30 bpm, P = 0.02), but recovered to normal level at one month follow-up (77.09 ± 11.97 bpm, P = 0.85). The right atrium, tricuspid valve annulus, and right ventricle dilated obviously one month after tricuspid regurgitation creation (dimension changes: 3.01 ± 0.35 vs. 3.56 ± 0.40 cm, P = 0.02; 2.92 ± 0.36 vs. 3.37 ± 0.39 cm, P = 0.01; 3.06 ± 0.42 vs. 3.60 ± 0.47 cm, P = 0.03 respectively). Autopsy findings showed that rupture of leaflet and/or chordae tendineae finally led to the tricuspid regurgitation. CONCLUSIONS: Severe tricuspid regurgitation can be created by a simple and effective percutaneous approach with a grasping forceps in swine model and right heart dilation can be observed consistently at one-month follow-up. This model will be valuable in pre-clinical studies for developing new tricuspid valve repair or replacement technique to treat severe tricuspid regurgitation.

Design Variation, Implantation, and Outcome of Transcatheter Mitral Valve Prosthesis: A Comprehensive Review.

The transcatheter mitral valve prosthesis is ideally suited for patients with inoperable mitral etiology. The transcatheter mitral valve implantation (TMVI) procedure has closely followed the evolution of transcatheter aortic procedures. There are considerable design variations amongst the limited TMVI prostheses currently available, and the implantation profiles of the devices are notably different. This comprehensive review will provide an overview of the current clinically tried TMVI devices with a focused outcome analysis. In addition, we have discussed the various design characteristics of TMVI and its associated failure mode, implantation technology, delivery methods, first-in-man trials, and pivotal trial summary for the synthesis of recent evidence. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021255241, identifier: CRD42021255241.

An in vitro investigation into the hemodynamic effects of orifice geometry and position on left ventricular vortex formation and turbulence intensity.

In a healthy human cardiac system, a large asymmetric clockwise vortex present in the left ventricle (LV) efficiently diverts the filling jet from the mitral annulus to the left ventricular outflow track. However, prior clinical studies have shown that artificial mitral valve replacement can affect the formation of physiological vortex, resulting in overall flow instability in the LV. Lately, the findings from several recent hemodynamic studies seem to suggest that the native D-shaped mitral annulus might be a crucial factor in the development of this physiological flow pattern, with its inherent flow stability and formation of coherent structures within the LV. This study aims to investigate the effect of orifice shape and its position with respect to the posterior wall of the ventricle on vortical formation and turbulence intensity in the LV, by utilizing four separate orifice configurations within an in vitro left heart simulator. Stereo particle image velocimetry experiments were then carried out to characterize the downstream flow field of each configuration. Our findings demonstrate that the generation of the physiological left ventricular vortical flow was not solely dependent upon the orifice shape but rather the subsequent jet-wall interaction. The distance of the orifice geometric center from the left ventricular posterior wall plays a significant role in this jet-wall interaction, and thus, vortical flow dynamics.

Transcatheter aortic valve implantation in Asia.

The use of transcatheter aortic valve implantation (TAVI) to treat severe symptomatic aortic valve stenosis has increased exponentially in the last decade. This rapid expansion was seen predominantly in Western developed nations and has been fuelled by favorable results reported from a plethora of well-publicized randomized controlled trials, large retrospective series and national registries. Now, TAVI has become the standard of care for inoperable patients and an alternative to open surgery in patients who are at intermediate to high risk for open surgery. Notwithstanding these positive results, Asia has been relatively slow to adopt this technology despite a potentially large patient pool. Unique features of Asian medical environments and differences in Asian anatomy affecting TAVI uptake in Asia will be discussed. This article serves to outline the various challenging aspects of disseminating TAVI in Asian countries.

Mid-term study of transcatheter aortic valve implantation in an Asian population with severe aortic stenosis: two-year Valve Academic Research Consortium-2 outcomes.

INTRODUCTION: Transcatheter aortic valve implantation (TAVI) is an effective treatment for high-risk or inoperative patients with severe aortic stenosis. Given the unique characteristics of Asian populations, questions regarding mid-term outcomes in Asians undergoing TAVI have yet to be addressed. We evaluated the two-year clinical outcomes of TAVI in an Asian population using Valve Academic Research Consortium-2 definitions. METHODS: This prospective study recruited 59 patients from a major academic medical centre in Singapore. The main outcomes were two-year survival rates, peri-procedural complications, symptom improvement, valvular function and assessment of learning curve. RESULTS: Mean age was 76.8 years (61.0% male), mean body surface area 1.6 m2 and mean logistic EuroSCORE 18.7%. Survival was 93.2%, 86.0% and 79.1% at 30 days, one year and two years, respectively. At 30 days post TAVI, the rate of stroke was 1.7%, life-threatening bleeding 5.1%, acute kidney injury 25.0%, major vascular complication 5.1%, and new permanent pacemaker implantation 6.8%. 29.3% of TAVI patients were rehospitalised (47.1% cardiovascular-related) within one year. These composite outcomes were measured: device success (93.2%); early safety (79.7%); clinical efficacy (66.1%); and time-related valve safety (84.7%). Univariate analysis found these predictors of two-year all-cause mortality: logistic EuroSCORE (hazard ratio [HR] 1.07; p < 0.001); baseline estimated glomerular filtration rate (HR 0.97; p = 0.048); and acute kidney injury (HR 5.33; p = 0.022). Multivariate analysis identified non-transfemoral TAVI as a predictor of cardiovascular-related two-year mortality (HR 14.64; p = 0.008). CONCLUSION: Despite the unique clinical differences in Asian populations, this registry demonstrated favourable mid-term clinical and safety outcomes in Asians undergoing TAVI.

A D-Shaped Bileaflet Bioprosthesis which Replicates Physiological Left Ventricular Flow Patterns.

Prior studies have shown that in a healthy heart, there exist a large asymmetric vortex structure that aids in establishing a steady flow field in the left ventricle. However, the implantation of existing artificial heart valves at the mitral position is found to have a negative effect on this physiological flow pattern. In light of this, a novel D-shaped bileaflet porcine bioprosthesis (GD valve) has been designed based on the native geometry mitral valve, with the hypothesis that biomimicry in valve design can restore physiological left ventricle flow patterns after valve implantation. An in-vitro experiment using two dimensional particle velocimetry imaging was carried out to determine the hemodynamic performance of the new bileaflet design and then compared to that of the well-established St. Jude Epic valve which functioned as a control in the experiment. Although both valves were found to have similar Reynolds shear stress and Turbulent Kinetic Energy levels, the novel D-shape valve was found to have lower turbulence intensity and greater mean kinetic energy conservation.

Numerical Modeling of Intraventricular Flow during Diastole after Implantation of BMHV.

This work presents a numerical simulation of intraventricular flow after the implantation of a bileaflet mechanical heart valve at the mitral position. The left ventricle was simplified conceptually as a truncated prolate spheroid and its motion was prescribed based on that of a healthy subject. The rigid leaflet rotation was driven by the transmitral flow and hence the leaflet dynamics were solved using fluid-structure interaction approach. The simulation results showed that the bileaflet mechanical heart valve at the mitral position behaved similarly to that at the aortic position. Sudden area expansion near the aortic root initiated a clockwise anterior vortex, and the continuous injection of flow through the orifice resulted in further growth of the anterior vortex during diastole, which dominated the intraventricular flow. This flow feature is beneficial to preserving the flow momentum and redirecting the blood flow towards the aortic valve. To the best of our knowledge, this is the first attempt to numerically model intraventricular flow with the mechanical heart valve incorporated at the mitral position using a fluid-structure interaction approach. This study facilitates future patient-specific studies.

Design considerations and quantitative assessment for the development of percutaneous mitral valve stent.

Percutaneous heart valve replacement is gaining popularity, as more positive reports of satisfactory early clinical experiences are published. However this technique is mostly used for the replacement of pulmonary and aortic valves and less often for the repair and replacement of atrioventricular valves mainly due to their anatomical complexity. While the challenges posed by the complexity of the mitral annulus anatomy cannot be mitigated, it is possible to design mitral stents that could offer good anchorage and support to the valve prosthesis. This paper describes four new Nitinol based mitral valve designs with specific features intended to address migration and paravalvular leaks associated with mitral valve designs. The paper also describes maximum possible crimpability assessment of these mitral stent designs using a crimpability index formulation based on the various stent design parameters. The actual crimpability of the designs was further evaluated using finite element analysis (FEA). Furthermore, fatigue modeling and analysis was also done on these designs. One of the models was then coated with polytetrafluoroethylene (PTFE) with leaflets sutured and put to: (i) leaflet functional tests to check for proper coaptation of the leaflet and regurgitation leakages on a phantom model and (ii) anchorage test where the stented valve was deployed in an explanted pig heart. Simulations results showed that all the stents designs could be crimped to 18F without mechanical failure. Leaflet functional test results showed that the valve leaflets in the fabricated stented valve coapted properly and the regurgitation leakage being within acceptable limits. Deployment of the stented valve in the explanted heart showed that it anchors well in the mitral annulus. Based on these promising results of the one design tested, the other stent models proposed here were also considered to be promising for percutaneous replacement of mitral valves for the treatment of mitral regurgitation, by virtue of their key features as well as effective crimping. These models will be fabricated and put to all the aforementioned tests before being taken for animal trials.

Combined off-pump transapical transcatheter aortic valve implantation and minimally invasive direct coronary artery bypass.

Transcatheter aortic valve implantation has been shown to be an effective treatment for severe aortic stenosis in high-risk surgical patients. Many of these patients have significant coexisting coronary artery disease. We report the first case of combined off-pump transapical aortic valve implantation and minimally invasive direct coronary artery bypass via a left mini-thoracotomy in an 82-year-old man with significant comorbidities. This combined procedure is technically feasible and can be performed safely in selected patients with aortic stenosis and left anterior descending artery lesion that is not suitable for percutaneous intervention.

Transatrial transcatheter tricuspid valve-in-valve implantation of balloon expandable bioprosthesis.

Transcatheter valve-in-valve implantation into failing mitral and aortic bioprosthetic valves have been reported. This strategy avoids performing high-risk repeat cardiac surgery in elderly patients with multiple comorbidities. Tricuspid valve-in-valve implantation has not been described. We report a case of failing bioprosthetic tricuspid valve in a 48-year-old woman with carcinoid syndrome. We attempted a transatrial transcatheter approach and we successfully deployed a 26-mm Edwards Sapien balloon expandable bioprosthesis (Edwards Lifesciences, Irvine, CA) into a severely stenotic tricuspid bioprosthesis. This case demonstrates the technical feasibility and safety of this approach. Therefore, tricuspid valve-in-valve implantation may be a viable treatment alternative in carefully selected patients.

Acute fibrin deposition causing acute failure of two tissue pericardial valves.

We report the early failure of two tissue valves within hours of surgery due to the accumulation of cellular debris in two different institutions in the United Kingdom. The valves were both found at explant to be covered in a cellular material - possibly fibrin. From clinical experience and careful review of the literature we have found no other reports of such early valve failure due to the build up of material on the structure of the valve. This rare occurrence needs to be reported in the literature to forewarn clinicians of an early complication that may not be recognized yet.