The Direct Flow Medical Prosthesis as a Sutureless Device for Valve Replacement in Aortic Valve Regurgitation: A Feasibility Study

Objectives: Direct Flow Medical® (DF)-prosthesis has been introduced for TAVR procedures in patients with aortic stenosis. In aortic insufficiency however, this fully retrievable and repositionable prosthesis has been used in limited cases only. Its flexible frame might promote secure fixation by adapting smoothly to the aortic anulus. Aim of this study was to evaluate, if implantation into a non-calcified native anulus throughout conventional aortic valve replacement is feasible and to prove firm positioning throughout a pharmacologically induced hyperdynamic state.

Methods: 10 female landrace pigs were divided into two groups according to their body weight (group I (n = 6) 70–76 kg, group II (n = 4) 55–60 kg). Implantations of DF-prostheses were performed during cardiac arrest in an open chest procedure on CPB. Evaluation of positioning and staying in place during hypertensive conditions up to 200 mm Hg systolic BP induced by titration of epinephrine intravenously was performed via transoesophageal echocardiography after release of aortic X-clamp.

Results: In group I (n = 6), following anulus sizing of 23 mm with standard prosthesis sizers, one animal each received 23 mm- and 25 mm-DF-prosthesis. In four animals with anuli sized 25mm, 25mm-DF-valves were implanted in two cases, in two other pigs 27mm and 29mm valves each, respectively. By doing so, slight oversizing was intended. Dislocation of the prosthesis into the LV occurred after X-clamp release in all cases. Following this, second implantation was aimed for in all animals. To secure oversizing, annulorrhaphy to reduce anulus diameter by four millimeters in four pigs was performed. Nevertheless, dislocation occurred in all animals. In group II sizing was performed with Hegar dilators (25mm (n = 3), 27mm (n = 1)). All animals received 29 mm prostheses. No valve dislocated after X-clamp release, proper functioning was confirmed under TEE. Post-mortem exams equally showed flawless positioning of all prostheses.

Conclusion: Primarily caused by suboptimal sizing due to over-elastic, non-calcified, anulus tissue, dislocation of the DF-prosthesis into the LV occurred consecutively under slightly oversizing. Following more profound oversizing, no dislocation took place, 100% procedural success rate during hyperdynamic conditions was confirmed by TEE. The feasibility to implant DF-prostheses in a conventional sutureless fashion for aortic valve replacement in non-calcified aortic anuli was demonstrated.