4D-Flow MRI and Vector Ultrasound in the In-Vitro Evaluation of Surgical Aortic Heart Valves - a Pilot Study.

INTRODUCTION: The aim of this study was the initial investigation of 4D-Flow MRI and Vector Ultrasound as novel imaging techniques in the in-vitro analysis of hemodynamics in anatomical models. Specifically, by looking at the hemodynamic performance of state-of-the-art surgical heart valves in a 3D-printed aortic arch. METHODS: The mock circulatory loop simulated physiological, pulsatile flow. Two mechanical and three biological aortic valves prostheses were compared in a 3D-printed aortic arch. 4D magnetic resonance imaging and vector flow Doppler ultrasound served as imaging methods. Hemodynamic parameters such as wall shear stress, flow velocities and pressure gradients were analyzed. RESULTS: The flow analysis revealed characteristic flow-patterns in the 3D-printed aortic arch. The blood-flow in the arch presented complex patterns, including the formation of helixes and vortices. Higher proximal peak velocities and lower flow volumes were found for biological valves. CONCLUSION: The mock circulatory loop in combination with modern radiological imaging provides a sufficient basis for the hemodynamic comparison of aortic valves.

Effective orifice diameter: a new sizing parameter of surgical valve prostheses to inform valve selection.

Background: The labeled sizes of surgical valve prostheses and their discordance with the physical internal valve orifice sizes has long been a controversy in the cardiac surgery community, leading many to believe it to be a contributing factor in prosthesis-patient mismatch following valvular replacement surgery. In an attempt to address this issue, the International Organization for Standardization (ISO) 5840-2:2021 standard for surgical valve prostheses recommends that a new sizing parameter, namely, the effective orifice diameter, be provided in labeling by all manufacturers as an indicator of the true flow-passing capacity of a prosthetic valve. Methods: The ISO Cardiac Valves Working Group conducted a multi-laboratory round-robin study to investigate whether the effective orifice diameter of a prosthetic surgical valve could be derived repeatably and reproducibly through steady forward-flow testing. A total of seven valve models, each with multiple sizes, were tested, including a mechanical heart valve and multiple biological heart valves. Results: The round-robin study confirmed that the steady forward-flow test had good intra-laboratory repeatability and inter-laboratory reproducibility in deriving the effective orifice diameters of surgical valve prostheses. On average, among the participating laboratories, the experimentally derived effective orifice diameter of a prosthetic heart valve was 3-12 mm smaller than its labeled size. Conclusions: The effective orifice diameter provides better characterization of the hydrodynamic characteristics of a surgical valve prosthesis and can be derived using a validated steady forward-flow test method. This new sizing parameter will soon be adopted by surgical valve manufacturers and provided in device labeling to inform valve selection by surgeons.

New Insights and Perspective on Bioprosthetic Valve Fracture From Bench Testing and Computed Tomography Analysis.

Background: Bioprosthetic valve fracture (BVF) during valve-in-valve TAVR (transcatheter aortic valve replacement) is a procedural adjunct designed to optimize the expansion of the transcatheter heart valve and reduce patient-prosthesis mismatch by using a high-pressure balloon to intentionally fracture the surgical heart valve (SHV). Methods: We performed bench testing on 15 bioprosthetic SHV to examine the optimal balloon size and pressure for BVF. We assessed morphological changes and expansion of SHV by computed tomography angiography. Successful BVF was defined as balloon waist disappearance on fluoroscopy and/or sudden pressure drop during balloon inflation. Results: Nine valves met the definition of BVF, 3 of which were confirmed by disruption of the stent frame. We classified surgical valves into 3 subsets: 1) fracturable with metal stent frame (MSF), 2) fracturable with polymer stent frame (PSF) and 3) nonfracturable. In general, valves with MSF were fractured using a balloon size = true internal diameter plus 3-5 mm inflated at high pressure (16-20 ATM) whereas valves with PSF could be fractured with a balloon size = true internal diameter plus 3-5 mm and lower balloon pressure (6-14 ATM). Gains in computed tomography angiography derived inflow area after BVF were 12.3% for MSF and 3.6% for PSF SHV. Conclusions: Gains in CT-determined valve area after BVF depend on the physical properties of the SHV, which in turn influences pressure thresholds and balloon sizing strategy for optimal BVF. Elastic recoil of PSF valves limits the gains in inflow area after BVF.

Early Feasibility Study of a Hybrid Tissue-Engineered Mitral Valve in an Ovine Model.

Tissue engineering aims to overcome the current limitations of heart valves by providing a viable alternative using living tissue. Nevertheless, the valves constructed from either decellularized xenogeneic or purely biologic scaffolds are unable to withstand the hemodynamic loads, particularly in the left ventricle. To address this, we have been developing a hybrid tissue-engineered heart valve (H-TEHV) concept consisting of a nondegradable elastomeric scaffold enclosed in a valve-like living tissue constructed from autologous cells. We developed a 21 mm mitral valve scaffold for implantation in an ovine model. Smooth muscle cells/fibroblasts and endothelial cells were extracted, isolated, and expanded from the animal's jugular vein. Next, the scaffold underwent a sequential coating with the sorted cells mixed with collagen type I. The resulting H-TEHV was then implanted into the mitral position of the same sheep through open-heart surgery. Echocardiography scans following the procedure revealed an acceptable valve performance, with no signs of regurgitation. The valve orifice area, measured by planimetry, was 2.9 cm2, the ejection fraction reached 67%, and the mean transmitral pressure gradient was measured at 8.39 mmHg. The animal successfully recovered from anesthesia and was transferred to the vivarium. Upon autopsy, the examination confirmed the integrity of the H-TEHV, with no evidence of tissue dehiscence. The preliminary results from the animal implantation suggest the feasibility of the H-TEHV.

The influence of metabolic syndrome in heart valve intervention. A multi-centric study.

BACKGROUND: The effect of metabolic syndrome (MetS), defined as insulin resistance along with two or more of: obesity, atherogenic dyslipidaemia and elevated blood pressure, on postoperative complications after isolated heart valve intervention remains controversial. We hypothesized that MetS may negatively influence the postoperative course in these patients. METHODS: Patients from 10 cardiac units who underwent isolated valve intervention (mitral ± $\pm $ tricuspid repair/replacement (mitral valve surgery [MVS]) or surgical aortic valve replacement (SAVR), or transcatheter aortic valve replacement (TAVR) were included. MetS was defined according to the World Health Organization criteria. Primary outcome was in-hospital mortality and overall postoperative length of stay (LOS). Relevant postoperative complications were also recorded. RESULTS: From 2010 to 2019, 17,283 patients underwent valve intervention. The MVS, SVAR, and TAVR accounted for the 39.4%, 48.2%, and 12.3% respectively of the whole. MetS compared to no-MetS was associated to higher mortality in the MVS group (6.5% vs. 2%, p < .001), but not in the SAVR and TAVR group. In both surgical cohorts, MetS was associated with increased complications including red blood cells transfusion, renal failure, mechanical ventilation time, intensive care and overall postoperative LOS (11 (9) vs. 10 (6), p < .001 and 10 (6) versus 10 (5) days, p = .002, MVS and [SAVR]). No differences were found in the TAVR cohort, with similar mortality and complications. CONCLUSION: MetS was associated to more postoperative complications, with higher mortality in the MVS group. In the TAVR cohort, postoperative complications and mortality rate did not differ between patients with and without MetS, however LOS was longer in the MetS group.

Long-term durability of a new surgical aortic valve: A 1 billion cycle in vitro study.

Background: This study assessed the long-term hemodynamic functional performance of the new Inspiris Resilia aortic valve after accelerated wear testing (AWT). Methods: Three 21-mm and 23-mm Inspiris valves were used for the AWT procedure. After 1 billion cycles (equivalent to 25 years), the valves' hemodynamic performance was compared with that of the corresponding zero-cycled condition. Next, 1 AWT cycled valve of each valve size was selected at random for particle image velocimetry (PIV) and leaflet kinematic tests, and the data were compared with data for an uncycled Inspiris Resilia aortic valve of the same size. PIV was used to quantitatively evaluate flow fields downstream of the valve. Valves were tested according to International Standards Organization 5840-2:2015 protocols. Results: The 21-mm and 23-mm valves met the International Organization for Standardization (ISO) durability performance requirements to 1 billion cycles. The mean effective orifice areas for the 21-mm and 23-mm zero-cycled and 1 billion-cycled valves were 1.89 ± 0.02 cm2 and 1.94 ± 0.01 cm2, respectively (P < .05) and 2.3 ± 0.13 cm2 and 2.40 ± 0.11 cm2, respectively (P < .05). Flow characterization of the control valves and the study valves demonstrated similar flow characteristics. The velocity and shear stress fields were also similar in the control and study valves. Conclusions: The Inspiris Resilia aortic valve demonstrated very good durability and hemodynamic performance after an equivalent of 25 years of simulated in vitro accelerated wear. The study valves exceeded 1 billion cycles of simulated wear, 5 times longer than the standard requirement for a tissue valve as stipulated in ISO 5840-2:2015.

Distance between valvular leaflet and coronary ostium predicting risk of coronary obstruction during TAVR.

BACKGROUND: The aim of this study was to evaluate the role of the distance between the aortic valve in projected position to the coronary ostium to determine risk of coronary artery obstruction after transcatheter aortic valve replacement (TAVR). METHODS: An Expected Leaflet-to-ostium Distance (ELOD) was obtained on pre-TAVR planning computed tomography by subtracting leaflet thickness and the distances from the center to the annular rim at annulus level and from the center to the coronary ostium at mid-ostial level. Variables were compared between patients with and without coronary obstruction and the level of association between variables was assessed using log odds ratio (OR). RESULTS: A total of 177 patients with 353 coronary arteries was analyzed. Mean annulus diameters (22.8 ± 2.8 mm and 23.4 ± 1.0 mm, p > 0.05) and mean sinus of Valsalva (SOV) diameters (31.2 ± 3.6 mm and 31.9 ± 3.6 mm, p > 0.05) were similar between patients with lower and higher coronary heights, respectively. There were three coronary obstruction cases. ELOD ≤ 2 mm in combination with leaflet length longer than mid-ostial height allowed for discrimination of cases with and without coronary obstruction. There was a significant association between coronary obstruction event and ELOD ≤ 2 mm (log OR = 6.180, p < 0.001). CONCLUSIONS: Our study showed that a combination of ELOD < 2 mm and a longer leaflet length than mid-ostial height may be associated with increased risk for coronary obstruction during TAVR.

Current state of transcatheter mitral valve implantation in bioprosthetic mitral valve and in mitral ring as a treatment approach for failed mitral prosthesis.

With heightened awareness of mitral valve disease and improvement in surgical techniques, the use of mitral valve bioprostheses has increased. There is a large aging population with prior surgical valvular interventions. Limited durability of the prosthesis due to valvular degeneration over time may necessitate the need for repair or replacement of the prior prosthesis in the future. This usually entails another surgical intervention in this population with elevated risk for a reoperation. There is an ongoing clinical need for newer, less invasive options that are feasible and carry a lower complication rate. The advent of transcatheter heart valve (THV) therapies has opened up a wide range of therapeutic options for treatment of a failed bioprosthesis. Their safety and feasibility are now well established. This article serves as a review of the currently available THVs for implantation in the mitral position, the pre-procedural assessment, the challenges associated with implantation, as well as outcomes associated with a mitral valve-in-valve (VIV) and a mitral valve-in-ring (VIR) procedure.

Valve Cracking Before Valve-In-Valve Transcatheter Aortic Valve Implantation to Treat Severe Paravalvular Leak.

A patient with severe bioprosthesic patient-prosthesis mismatch, severe paravalvular leak, and symptoms of heart failure New York Heart Association functional class III was successfully treated using valve cracking followed by valve-in-valve transcatheter aortic valve implantation with excellent results at 1-year follow-up. (Level of Difficulty: Advanced.).

Challenges in valve-in-valve therapy.

At present, the majority of surgical heart valves (SHVs) implanted are bioprosthetic valves. Over time however, these are prone to structural deterioration, which may manifest as valvular stenosis, regurgitation or a combination of the two. Re-operation is the current standard of care for these patients but this itself carries a significant risk of mortality and morbidity. As a natural extension of transcatheter aortic valve implantation (TAVI), now an evidence based solution for severe aortic stenosis in high-risk patients, valve-in-valve (VIV) therapy is evolving into an alternative option in selected patients with structural biological valvular deterioration in all four-valve positions. The first of these VIV procedures was performed in Germany in 2007, for failing aortic valve prosthesis and later, reported in other positions. As with any novel emerging therapy, there is a learning curve to the procedure and the operator must be aware of the potential challenges. In this review we describe some of these challenges with the aim of providing awareness as well as guidance on attaining a successful outcome.

Valve-in-valve procedure: importance of the anatomy of surgical bioprostheses.

Transcatheter aortic valve implantation is an accepted and established alternative to surgical aortic valve replacement for patients with severe symptomatic aortic valve stenosis and multiple comorbidities that would make open surgery a high-risk option. It has also evolved as a suitable treatment option for degenerative surgical heart valve disease, with considerable experience in the aortic and mitral positions. To enable a successful procedure, avoiding malposition, valve embolization and coronary obstruction, clinicians should be familiar with the design, fluoroscopic appearances and implantation technique of the degenerated surgical bioprosthetic valve in situ, as well as its compatibility with currently available transcatheter valves.

Fluoroscopic guide to an ideal implant position for Sapien XT and CoreValve during a valve-in-valve procedure.

OBJECTIVES: This study sought to provide a guide to the fluoroscopic appearances of various valve-in-valve (VIV) combinations by deploying a transcatheter heart valve (THV) within a degenerated surgical heart valve (SHV) in an ideal position. BACKGROUND: VIV procedures are being increasingly performed with substantial experience acquired in treating degenerated SHV in the aortic position with Sapien/Sapien XT (Edwards Lifesciences Ltd., Irvine, California) and CoreValve/Evolute (Medtronic Inc., Minneapolis, Minnesota) valves. Although less invasive than conventional surgery, securing the THV in an optimal position within the SHV determines the success of this novel treatment. METHODS: For VIV implantation, we selected appropriate Sapien XT and CoreValve/Evolute sizes depending on the internal diameter of the SHV. Implantation was performed in vitro. In case of the Sapien XT valve, it was deployed 4 to 5 mm below the sewing ring of the SHV, whereas the CoreValve/Evolute was deployed 5 mm below the level of the sewing ring. Photographs and fluoroscopic images of the various VIV combinations were obtained in side profile to study the ideal position and end-on profile to study the circularity of the THV. RESULTS: Fluoroscopic images obtained in side profile highlighted the differences in various VIV combinations, as all SHV are unique in their fluoroscopic appearances. Also, all THV implants in various VIV combinations achieved a nearly circular shape. CONCLUSIONS: To achieve an optimal result when considering VIV, it is important to be familiar with the structure and fluoroscopic appearances of the failed SHV, the THV used, and their combination.