Catheter-Implanted Prosthetic Heart Valves

Abstract

A new expandable artificial heart valve was developed for implantation by a transluminal catheter technique without using thoracotomy or extracorporeal circulation. The aim of this study was to implant the valve in isolated vessels of the descending thoracic aorta as well as in closed chest pigs, and furthermore to study the prosthesis' mechanical stability and the valve function. The artificial valve was made by mounting a porcine aortic valve on an expandable stent. Before implantation, the stent-valve was compressed on a deflated balloon catheter and mounted inside an introducer sheath. After intravascular introduction to the descending thoracic aorta the stent-valve was discharged from the sheath. Implantation was performed by balloon inflation which expanded the stent-valve to a diameter exceeding the internal vessel's diameter. After balloon deflation the stent-valve maintained an expanded configuration ensuring a stable fixation against the vessel wall. In vitro implantations were performed in 36 isolated descending thoracic aorta specimens obtained from 80 kg pigs. Mechanical stability was evaluated by applying a downing load to the prosthesis. No displacement occurred at loads < or = 1 kg when a large balloon (31 mm) was used for implantation. Transvalvular pressure differences between 11-47 mmHg (median) were obtained at antegrade flowrates between 5-8 l/min. Furthermore, only moderate leakage flows were measured during retrograde perfusion. In vivo implantations were performed in six 80 kg pigs. Implantation was safe and easy, and angiograph and haemodynamic evaluations revealed essentially no stenosis or regurgitation. No complications in migration, perforation, hemorrhage or thrombosis were observed. This study indicates a good mechanical stability and valve function of the new expandable artificial valves.