In-hospital outcomes and predictors of paravalvular leak and deep implantation with the Evolut-R 34 mm device: A comparison with smaller Evolut-R sizes

PURPOSE

To compare in-hospital outcome of Evolut-R 34 mm vs. smaller Evolut-R devices and to identify predictors of paravalvular leak (PVL) and deep implantation specific for Evolut-R 34 mm.

METHODS

This single-center retrospective study included 359 consecutive patients undergoing transcatheter aortic valve replacement (TAVR) with Evolut-R 34 mm (N = 84,23.4%) and Evolut-R 23/26/29 mm (N = 275,76.6%) between 2016 and 2019.

RESULTS

Patients in Evolut-R 34 mm group were more frequently males, had lower STS score, ejection fraction, and mean aortic gradient compared to the Evolut-R 23/26/29 mm group. Horizontal aorta and large LVOT were more frequent findings in the Evolut-R 34 mm group, whereas calcium volume was comparable among the groups. During TAVR, mean implantation depth and contrast volume were greater in the Evolut-R 34 mm group, compared to the Evolut 23/26/29 mm group. Post-procedurally, 30-day mortality, ≥moderate PVL, device success and pacemaker implantation (PM) rates were comparable between groups. Among independent predictors of ≥moderate PVL, calcium volume (OR:1.04; p < 0.001) was predictive with different thresholds in both groups, whereas aortic angulation (OR:1.40; p = 0.005) was predictive only in Evolut-R 34 mm group at a cutoff of 60° (AUC:0.73; p = 0.043). Body weight (OR:1.03; p = 0.027), left ventricular outflow tract (LVOT) diameter (OR:1.34; p = 0.001), and mean aortic gradient (OR:0.96; p = 0.006) were independent predictors of deep implantation (mean depth ≥ 6 mm), with LVOT>27 mm being predictive specifically for Evolut-R 34 mm (AUC:0.66; p = 0.024).

CONCLUSIONS

TAVR with Evolut-R 34 mm and Evolut-R 23/26/29 mm showed comparable in-hospital outcome. Aortic angulation >60° and LVOT >27 mm were predictive respectively of ≥moderate PVL and deep implantation specifically in Evolut-R 34 mm patients.

Bioprinted 3D vascularized tissue model for drug toxicity analysis

To develop biomimetic three-dimensional (3D) tissue constructs for drug screening and biological studies, engineered blood vessels should be integrated into the constructs to mimic the drug administration process in vivo. The development of perfusable vascularized 3D tissue constructs for studying the drug administration process through an engineered endothelial layer remains an area of intensive research. Here, we report the development of a simple 3D vascularized liver tissue model to study drug toxicity through the incorporation of an engineered endothelial layer. Using a sacrificial bioprinting technique, a hollow microchannel was successfully fabricated in the 3D liver tissue construct created with HepG2/C3A cells encapsulated in a gelatin methacryloyl hydrogel. After seeding human umbilical vein endothelial cells (HUVECs) into the microchannel, we obtained a vascularized tissue construct containing a uniformly coated HUVEC layer within the hollow microchannel. The inclusion of the HUVEC layer into the scaffold resulted in delayed permeability of biomolecules into the 3D liver construct. In addition, the vascularized construct containing the HUVEC layer showed an increased viability of the HepG2/C3A cells within the 3D scaffold compared to that of the 3D liver constructs without the HUVEC layer, demonstrating a protective role of the introduced endothelial cell layer. The 3D vascularized liver model presented in this study is anticipated to provide a better and more accurate in vitro liver model system for future drug toxicity testing.

Bioprinted thrombosis-on-a-chip

Pathologic thrombosis kills more people than cancer and trauma combined; it is associated with significant disability and morbidity, and represents a major healthcare burden. Despite advancements in medical therapies and imaging, there is often incomplete resolution of the thrombus. The residual thrombus can undergo fibrotic changes over time through infiltration of fibroblasts from the surrounding tissues and eventually transform into a permanent clot often associated with post-thrombotic syndrome. In order to understand the importance of cellular interactions and the impact of potential therapeutics to treat thrombosis, an in vitro platform using human cells and blood components would be beneficial. Towards achieving this aim, there have been studies utilizing the capabilities of microdevices to study the hemodynamics associated with thrombosis. In this work, we further exploited the utilization of 3D bioprinting technology, for the construction of a highly biomimetic thrombosis-on-a-chip model. The model consisted of microchannels coated with a layer of confluent human endothelium embedded in a gelatin methacryloyl (GelMA) hydrogel, where human whole blood was infused and induced to form thrombi. Continuous perfusion with tissue plasmin activator led to dissolution of non-fibrotic clots, revealing clinical relevance of the model. Further encapsulating fibroblasts in the GelMA matrix demonstrated the potential migration of these cells into the clot and subsequent deposition of collagen type I over time, facilitating fibrosis remodeling that resembled the in vivo scenario. Our study suggests that in vitro 3D bioprinted blood coagulation models can be used to study the pathology of fibrosis, and particularly, in thrombosis. This versatile platform may be conveniently extended to other vascularized fibrotic disease models.

Bioprinting 3D microfibrous scaffolds for engineering endothelialized myocardium and heart-on-a-chip

Engineering cardiac tissues and organ models remains a great challenge due to the hierarchical structure of the native myocardium. The need of integrating blood vessels brings additional complexity, limiting the available approaches that are suitable to produce integrated cardiovascular organoids. In this work we propose a novel hybrid strategy based on 3D bioprinting, to fabricate endothelialized myocardium. Enabled by the use of our composite bioink, endothelial cells directly bioprinted within microfibrous hydrogel scaffolds gradually migrated towards the peripheries of the microfibers to form a layer of confluent endothelium. Together with controlled anisotropy, this 3D endothelial bed was then seeded with cardiomyocytes to generate aligned myocardium capable of spontaneous and synchronous contraction. We further embedded the organoids into a specially designed microfluidic perfusion bioreactor to complete the endothelialized-myocardium-on-a-chip platform for cardiovascular toxicity evaluation. Finally, we demonstrated that such a technique could be translated to human cardiomyocytes derived from induced pluripotent stem cells to construct endothelialized human myocardium. We believe that our method for generation of endothelialized organoids fabricated through an innovative 3D bioprinting technology may find widespread applications in regenerative medicine, drug screening, and potentially disease modeling.

From cardiac tissue engineering to heart-on-a-chip: beating challenges

The heart is one of the most vital organs in the human body, which actively pumps the blood through the vascular network to supply nutrients to as well as to extract wastes from all other organs, maintaining the homeostasis of the biological system. Over the past few decades, tremendous efforts have been exerted in engineering functional cardiac tissues for heart regeneration via biomimetic approaches. More recently, progress has been made toward the transformation of knowledge obtained from cardiac tissue engineering to building physiologically relevant microfluidic human heart models (i.e. heart-on-chips) for applications in drug discovery. The advancement in stem cell technologies further provides the opportunity to create personalized in vitro models from cells derived from patients. Here, starting from heart biology, we review recent advances in engineering cardiac tissues and heart-on-a-chip platforms for their use in heart regeneration and cardiotoxic/cardiotherapeutic drug screening, and then briefly conclude with characterization techniques and personalization potential of the cardiac models.