Maximilian Kütting

Polyurethane heart valves: past, present and future

Replacement cardiac valves have been in use since the 1950s, and today represent the most widely used cardiovascular devices. One type of replacement cardiac valve, the polyurethane heart valve, has been around since the first stages of prosthesis development, and has made advances along with the development of biological and mechanical heart valves over the past 60 years. During this time, problems with durability and biocompatibility have held back polyurethane valves, but progress in materials and manufacturing techniques can lead the way to a brighter future for these devices and their huge potential. This article describes previous efforts to manufacture polyurethane heart valves, highlights the challenges of manufacturing and explains the factors influencing durability and successful functioning of such a device.

A novel approach to an anatomical adapted stent design for the percutaneous therapy of tricuspid valve diseases: preliminary experiences from an engineering point of view.

Tricuspid valve regurgitation mostly occurs as result of dilation of the right ventricle, secondary to left heart valve diseases. Until recently, little attention has been given to the development of percutaneous therapeutic tools exclusively designed for tricuspid valve disease. A new approach to the interventional therapy of tricuspid regurgitation, in particular, the design of a conceptual new valve-bearing, self-expansible stent, is presented here. A three-dimensional computer model of a right porcine heart was developed to gain a realistic anatomical geometry. The new design consists of two tubular stent elements, one inside the superior vena cava and the other inside the tricuspid valve annulus after being eventually equipped with a biological valve prosthesis, which are connected by struts. Anchoring to the heart structure is provided primarily by the vena cava stent, strengthened by the struts. The stents are designed to be cut from a 10 mm tube and later expanded to their designated diameter. Simulation software analyzing the expansion process with respect to the intended geometrical design is used in an iterative process. A validation of the anatomical geometry and function of the stent design inside a silicone model within in vitro tests and a random porcine heart shows an accurate anatomical fitting.

What can be done for cerebral embolic protection in TAVI? Analysis in the light of 10 years’ experience with protected carotid artery stenting

In the last 30 years, development of minimally invasive percutaneous procedures to treat cardiovascular defects has been thriving. Although these techniques present obvious advantages, like avoiding cardiopulmonary bypass, the passage of catheter systems and the deployment of devices in the blood circulation can cause particle embolization that may result in stroke. In carotid artery stenting, cerebral embolic protection devices (CEPD) such as filtering membranes have been available for already 10 years. In transcatheter aortic valve implantation (TAVI), the development of CEPD is starting and three membrane-based devices are in clinical trials. There are controversial discussions about the efficacy of CEPD in TAVI. The experience with CEPD in carotid artery stenting can help to understand some of the technical issues and shortcomings of current devices and thereby ultimately reduce cerebral complication risks during TAVI procedures.

Development of a Transcatheter Tricuspid Valve Prosthesis Through Steps of Iterative Optimization and Finite Element Analysis.

The development of a transcatheter tricuspid valve prosthesis for the treatment of tricuspid regurgitation (TR) is presented. The design process involves an iterative development method based on computed tomography data and different steps of finite element analysis (FEA). The enhanced design consists of two self-expandable stents, one is placed inside the superior vena cava (SVC) for primary device anchoring, the second lies inside the tricuspid valve annulus (TVA). Both stents are connected by flexible connecting struts (CS) to anchor the TVA-stent in the orthotopic position. The iterative development method includes the expansion and crimping of the stents and CS with FEA. Leaflet performance and leaflet-stent interaction were studied by applying the physiologic pressure cycle of the right heart onto the leaflet surfaces. A previously implemented nitinol material model and a new porcine pericardium material model derived from uniaxial tensile tests were used. Maximum strains/stresses were approx. 6.8% for the nitinol parts and 2.9 MPa for the leaflets. Stent displacement because of leaflet movement was ≤1.8 mm at the commissures and the coaptation height was 1.6-3 mm. This led to an overall good performance of the prosthesis. An anatomic study showed a good anatomic fit of the device inside the human right heart.

Dual source computed tomography based analysis of stent performance, its association with valvular calcification and residual aortic regurgitation after implantation of a balloon-expandable transcatheter heart valve

Objectives The aim of this study was to investigate the mutual influence of valvular calcifications and transcatheter aortic valve stent geometry during and after implantation of a balloon-expandable SAPIEN ® /SAPIEN XT ® prostheses. Aortic valve calcification has been linked with adverse complications after transcatheter aortic valve implantation (TAVI). However, little is known about the fate of the calcifications after TAVI as well as its influence on transcatheter heart valve geometry. Methods Thirty one patients underwent cardiac dual source computed tomography (DSCT) before and after a TAVI with the Edwards SAPIEN/SAPIEN XT ® prostheses. Detailed DSCT image analysis was performed with Mimics ® and 3Matic ® (both Materialise, Leuven, Belgium). Results Implanted stents reached an average degree of expansion of 84% and achieved good circularity despite the presence of fairly oval native annuli and a heterogeneous degree of valvular calcification. Both, the degree of stent expansion and the degree of stent eccentricity were inversely related to the degree of oversizing, but independent of the degree of valvular calcification and native annular ovality. Visualization of the position of calcific debris before and after TAVI showed that calcifications were shifted upwards and outwards as a consequence of the implantation procedure. The degree of stent eccentricity was related to residual aortic regurgitation grade ≥2. Conclusions The SAPIEN ® /SAPIEN XT ® prostheses achieved good degrees of stent expansion and circularity regardless of the morphology of the landing zone. Increased stent ovality was associated with an elevated risk for aortic regurgitation. The total calcification volume, degree of annular ovality and stent expansion were not associated with residual AR.

Preclinical determination of the best functional position for transcatheter heart valves implanted in rapid deployment bioprostheses

AIMS The aim of this study was to determine the best functional position of a transcatheter heart valve (THV) implanted as a valve-in-valve (ViV) procedure in small rapid deployment valves (RDV) in an in vitro model. METHODS AND RESULTS A 21 mm Perceval, Enable or INTUITY RDV was mounted into a pulse duplicator and a 23 mm balloon-expandable or a self-expanding THV was deployed (valve-in-valve) in two different positions. Under physiological hydrodynamic conditions, the performance of the THV was characterised by mean transvalvular pressure gradient (MPG), effective orifice area (EOA) and regurgitation volume (RV). Leaflet kinematics were assessed with high-speed video recordings, and X-ray images were acquired. All THV/RDV combinations met ISO requirements regarding hydrodynamic performance. In most cases, the higher position of the THV performed better than the lower one in terms of a lower MPG and increased EOA. Leaflet motion of the implanted THV was impaired in the lower position. In contrast, regurgitation volumes were relatively small and similar, regardless of the THV position. CONCLUSIONS ViV implantation of a THV in a small RDV yielded satisfactory hydrodynamic results. In most cases, a high implantation position achieved lower MPG, higher EOA and a reduced risk of impaired THV leaflet function. Fluoroscopy images of the best functional ViV positions are presented as a blueprint for patient procedures.

Using 3D Physical Modeling to Plan Surgical Corrections of Complex Congenital Heart Defects.

Background Understanding the anatomy and physiology of congenital heart defects is crucial for planning interventions in these patients. Congenital heart procedures often involve complex three‐dimensional (3D) reconstructions. Excellent imaging techniques are required to depict all anatomical details. We have used and evaluated fast 3D prototyping technology for reconstruction and planning of corrections of complex congenital heart defects. Materials and Methods 3D physical models were constructed from contrast‐enhanced computed tomography (CT) datasets of patients with complex congenital heart defect. Two different commercially available printing technologies were used and their clinical application compared. Results Physical models of three different patients were used for preoperative surgical planning. All models showed good correspondence to patient anatomy. Both printing technologies gave excellent results. Conclusion Physical models could be easily constructed with the use of CT datasets. The printing process could be done efficiently, quite rapidly, and cost effectively. Surgical corrections could be planned based on these models.

Eccentricity of the aortic annulus is not associated with functional impairment of the transapical Jenavalve in an in vitro hydrodynamic test model

Stephan Ensminger, Stephan Achenbach, Jochen Boergermann, Jan Gummert, Smita R. Jategaonkar, Maximilian Kuetting, Annika Schuhbaeck, Ulrich Steinseifer, Marc Utzenrath Heart and Diabetes Center NRW, Ruhr University Bochum, Bad Oeynhausen, Germany, University of Erlangen, Erlangen, Germany, Heart and Diabetes Center NRW, Bad Oeynhausen, Germany, Institute of Applied Medical Engineering, Aachen, NRW, Friedrich-Alexander University of Erlangen-Nürnberg, Erlangen, Germany, Inst. forvApplied Medical Engineering, RWTH Aachen University, Aachen, NRW

Anchoring percutaneous heart valves

Percutaneous heart valve replacement is an exciting and innovative technology which provides new treatment options for previously untreatable patients. Despite promising clinical results for the currently available prostheses by Edwards Lifesciences and Medtronic, these devices still require improvement in order to represent a true alternative to conventional heart valve replacement surgery. One of these challenges is the safe and effective anchoring of the catheter-delivered devices. This paper describes the development of an anchoring technique and highlights the key anatomical influence factors to be considered when designing percutaneous heart valve prostheses.