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.
