Evaluation of pliable bioresorbable, elastomeric aortic valve prostheses in sheep during 12 months post implantation.

Pliable microfibrous, bioresorbable elastomeric heart valve prostheses are investigated in search of sustainable heart valve replacement. These cell-free implants recruit cells and trigger tissue formation on the valves in situ. Our aim is to investigate the behaviour of these heart valve prostheses when exposed to the high-pressure circulation. We conducted a 12-month follow-up study in sheep to evaluate the in vivo functionality and neo-tissue formation of these valves in the aortic position. All valves remained free from endocarditis, thrombotic complications and macroscopic calcifications. Cell colonisation in the leaflets was mainly restricted to the hinge area, while resorption of synthetic fibers was limited. Most valves were pliable and structurally intact (10/15), however, other valves (5/15) showed cusp thickening, retraction or holes in the leaflets. Further research is needed to assess whether in-situ heart valve tissue engineering in the aortic position is possible or whether non-resorbable synthetic pliable prostheses are preferred.

Valvulogenesis of a living, innervated pulmonary root induced by an acellular scaffold.

Heart valve disease is a major cause of mortality and morbidity worldwide with no effective medical therapy and no ideal valve substitute emulating the extremely sophisticated functions of a living heart valve. These functions influence survival and quality of life. This has stimulated extensive attempts at tissue engineering "living" heart valves. These attempts utilised combinations of allogeneic/ autologous cells and biological scaffolds with practical, regulatory, and ethical issues. In situ regeneration depends on scaffolds that attract, house and instruct cells and promote connective tissue formation. We describe a surgical, tissue-engineered, anatomically precise, novel off-the-shelf, acellular, synthetic scaffold inducing a rapid process of morphogenesis involving relevant cell types, extracellular matrix, regulatory elements including nerves and humoral components. This process relies on specific material characteristics, design and "morphodynamism".

Balancing the ventricular outputs of pulsatile total artificial hearts.

BACKGROUND: Maintaining balanced left and right cardiac outputs in a total artificial heart (TAH) is challenging due to the need for continuous adaptation to changing hemodynamic conditions. Proper balance in ventricular outputs of the left and right ventricles requires a preload-sensitive response and mechanisms to address the higher volumetric efficiency of the right ventricle. METHODS: This review provides a comprehensive overview of various methods used to balance left and right ventricular outputs in pulsatile total artificial hearts, categorized based on their actuation mechanism. RESULTS: Reported strategies include incorporating compliant materials and/or air cushions inside the ventricles, employing active control mechanisms to regulate ventricular filling state, and utilizing various shunts (such as hydraulic or intra-atrial shunts). Furthermore, reducing right ventricular stroke volume compared to the left often serves to balance the ventricular outputs. Individually controlled actuation of both ventricles in a pulsatile TAH seems to be the simplest and most effective way to achieve proper preload sensitivity and left-right output balance. Pneumatically actuated TAHs have the advantage to respond passively to preload changes. CONCLUSION: Therefore, a pneumatic TAH that comprises two individually actuated ventricles appears to be a more desirable option-both in terms of simplicity and efficacy-to respond to changing hemodynamic conditions.

The ongoing quest for the first total artificial heart as destination therapy.

Many patients with end-stage heart disease die because of the scarcity of donor hearts. A total artificial heart (TAH), an implantable machine that replaces the heart, has so far been successfully used in over 1,700 patients as a temporary life-saving technology for bridging to heart transplantation. However, after more than six decades of research on TAHs, a TAH that is suitable for destination therapy is not yet available. High complication rates, bulky devices, poor durability, poor biocompatibility and low patient quality of life are some of the major drawbacks of current TAH devices that must be addressed before TAHs can be used as a destination therapy. Quickly emerging innovations in battery technology, wireless energy transmission, biocompatible materials and soft robotics are providing a promising opportunity for TAH development and might help to solve the drawbacks of current TAHs. In this Review, we describe the milestones in the history of TAH research and reflect on lessons learned during TAH development. We summarize the differences in the working mechanisms of these devices, discuss the next generation of TAHs and highlight emerging technologies that will promote TAH development in the coming decade. Finally, we present current challenges and future perspectives for the field.

Strategies to Improve Survival from Surgery for Heart Valve Implantation in Sheep.

Sheep are a commonly used and validated model for cardiovascular research and, more specifically, for heart valve research. Implanting a heart valve on the arrested heart in sheep is complex and is often complicated by difficulties in restarting the heart, causing significant on-table mortality. Therefore, optimal cardioprotective management during heart valve implantation in sheep is essential. However, little is known about successful cardioprotective management techniques in sheep. This article reports our experience in the cardioprotective management of 20 female sheep that underwent surgical aortic valve replacement with a stented tissue-engineered heart valve prosthesis. During this series of experiments, we modified our cardioprotection protocol to improve survival. We emphasize the importance of total body hypothermia and external cooling of the heart. Furthermore, we recommend repeated cardioplegia administration at 20 min intervals during surgery, with the final dosage of cardioplegia given immediately before the de-clamping of the aorta. To reduce the number of defibrillator shocks during a state of ventricular fibrillation (VF), we have learned to restart the heart by reclamping the aorta, administering cardioplegia until cardiac arrest, and de-clamping the aorta thereafter. Despite these encouraging results, more research is needed to finalize a protocol for this procedure.

A systematic evaluation on reporting quality of modern studies on pulmonary heart valve implantation in large animals.

OBJECTIVES: Before new heart valves can be implanted safely in humans, animal experiments have to be performed. These animal experiments have to be clearly designed, analysed and reported to assess the accuracy and importance of the findings. We aimed to provide an overview of the reporting and methodological quality of preclinical heart valve research. METHODS: We conducted a systematic literature search on biological and mechanical pulmonary valve implantations in large animals. We used the Animals in Research: Reporting In Vivo Experiments (ARRIVE) guidelines to score the quality of reporting in each article. We compared the scores before and after the introduction of the ARRIVE guidelines (2010). RESULTS: We screened 348 articles, of which 31 articles were included. The included articles reported a mean of 54.7% adequately scored ARRIVE items (95% confidence interval 52.2-57.3%). We did not identify a difference in reporting quality (54.7% vs 54.8%) between articles published before and after 2010. We found an unclear (lack of description) risk of selection bias, performance bias and detection bias. CONCLUSIONS: The reporting quality of studies that implanted bioprosthetic or mechanical valves in the pulmonary position in the large animal model is not on the desired level. The introduction of the ARRIVE guidelines in 2010 did not improve the reporting quality in this field of research. Hereby, we want to emphasize the importance of clearly describing the methods and transparently reporting the results in animal experiments. This is of great importance for the safe translation of new heart valves to the clinic. CLINICAL TRIAL REGISTRATION NUMBER: PROSPERO (CRD42019147895).

Improved acute haemodynamic response to cardiac resynchronization therapy using multipoint pacing cannot solely be explained by better resynchronization.

BACKGROUND: The recently developed quadripolar left ventricular (LV) leads have been developed to increase the benefit of cardiac resynchronization therapy (CRT). These leads offer the option to stimulate the LV on multiple sites (multipoint pacing, MPP). Invasive haemodynamic measurements have shown that MPP increases haemodynamic response. PURPOSE: To investigate whether the beneficial effect of MPP can be explained by better electrical resynchronization. METHODS: Different LV lead locations were tested during biventricular (BiV) pacing and MPP in 29 CRT candidates. The 12-lead electrocardiogram (ECG) and the invasive LV pressure curves were measured simultaneously. The Kors matrix was used to convert the ECG into a vectorcardiogram (VCG). The acute haemodynamic benefit of MPP was compared with the reduction in QRS duration and VCG-derived QRS area. RESULTS: Out of the 29 patients, three patients were excluded due to missing LV pressures or ECG measurements. In the remaining 26 patients MPP resulted in a significant haemodynamic improvement compared to BiV pacing without a significant change in QRS duration and QRS area. In only 5 out of the 26 patients the QRS area decreased during MPP compared to BiV pacing. In 17 patients MPP did not change QRS duration and significantly increased QRS area but moved the direction of the maximal QRS vector (azimuth) more opposite from baseline compared to BiV pacing. In 4 patients the QRS area was small during baseline, indicating limited electrical dyssynchrony. CONCLUSION: The acute haemodynamic benefit of MPP over BiV pacing is achieved by either electrical resynchronization (reduction in QRS area) or by a rotation of the maximal QRS vector, indicating a more LV dominated activation sequence. The latter property was found in two-thirds of the cohort studied.