A new approach to the interventional therapy of tricuspid regurgitation.

Currently, there are no fully developed interventional approaches for the treatment of tricuspid regurgitation (TR). The aim of this study was to evaluate the feasibility of orthotopic interventional placement of a biological prosthetic valve in the tricuspid position by inserting, with a transvenous approach, a self-expandable valve-bearing stent into the right atrium. Based on findings of computerized tomography (CT), a model of the porcine right heart was obtained. A self-expanding vascular endoprosthesis, carrying a prosthetic heart valve, was reshaped to fit the superior vena cava and the tricuspid annulus. Fenestrations were created to allow blood flow from the inferior vena cava and coronary sinus. This new device ("tricuspid endoprosthesis": TE) was implanted operatively into the superior vena cava, right atrium, and tricuspid annulus in six pigs. CT demonstrated proper fitting of the device, and echocardiography demonstrated correct positioning and function of the TE. Five animals were successfully weaned from cardiopulmonary bypass. Autopsy confirmed correct positioning of the TE without major trauma to surrounding tissues. These findings demonstrate a complete interventional approach for treating TR.

Cranioplasty with customized titanium and PEEK implants in a mechanical stress model.

Large skull defects as a result of craniectomies due to cerebral insults, trauma, or tumors create functional and aesthetic disturbances for the patient. Cranioplasty with implants in these cases are an alternative to autogenous bone transplantation. In our clinic, customized titanium or optima poly-ether-ether ketone (PEEK) implants are used to reconstruct craniectomy defects. To compare the two materials we investigated the structural changes of the implants fixed to a sintered polyamide skull model under mechanical stress in four simplified models. In a standard testing machine, the models were subjected to a load under a quasi-static loading rate of 1.925 mm/min. Fractures of the PEEK implants occurred at a force of 24.2 and 24.5 kN with a displacement of 8.4 and 8 mm. The titanium implants showed no deformation, but extensive damage was seen in the polyamide skull models. The highest pressures achieved were 45.8 and 50.9 kN. In a simplified model with quasi-static loading, both implants withstood forces that were higher than those capable of causing skull fractures. It seems that the mechanical properties of PEEK could provide better protection when used for cranioplasty in patients after craniectomy if reconstruction with autogenous bone is not possible.

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.