Background: Aortic valve replacement (AVR) using extracorporeal circulation is currently the treatment of choice for symptomatic aortic stenosis. However, patients with multiple high-risk comorbid conditions may benefit from reduced ECC time by a simplified and faster resection in conjunction with quick sutureless valve implantation. Methods: A prototype of a new minimally invasive aortic valve resection tool equipped with rotating and foldable Nitinol cutting edges was designed. Commercially available aortic valve bioprostheses were artificially calcified (group 1: moderate calcified, n = 8, group 2: severely calcified, n = 8). In vitro resection was performed using a 21 mm cutting blade. Resection time (RT), maximum turning moment (MTM) and number of required rotations (NR) were measured. Furthermore, particle generation during the process of cutting was obtained and quantified. Results: Aortic valve cutting could be obtained without any complications in all cases. Cutting process resulted in a RTof 15.5 AE 3 s in group 1 compared to 34.9 AE 15 s in group 2 ( p = 0.005), MTM was 3 AE 0.6 N m in group 1 compared to 3.5 AE 0.6 N m in group 2 ( p = 0.068) and NR were 30.6 AE 2.3 in group 1 compared to 48.1 AE 15.5 in group 2 ( p = 0.007). Particle generation was 1.77 AE 0.17 g in group 1 compared to 1.41 AE 0.44 g in group 2 ( p = 0.047). Conclusions: These first in vitro results confirm feasibility and accelerated aortic valve resection within 30 s. This new concept holds promise for very fast AVR in combination with insertion of sutureless aortic valve prosthesis, targeting for ischemic times less than 10 min in the open heart situation. Finally, resection and percutaneous AVR within 1 min in the beating heart situation is envisioned. #

The present study clearly confirmed ability of an accelerated cutting of stenotic aortic valve by the aortic valve resection tool. Nearly all leaflets were cut and a small rim was left within the annulus, hence providing an ideal 'landing zone' for the new prosthesis. Nevertheless, the aortic valve resection tool should be enhanced by adding a centering mechanism, thus achieving a more precise cutting process in order to avoid secondary damage.

The use of minimally invasive techniques for aortic valve replacement (AVR) may be limited for severely calcified and degenerated stenotic aortic valves. A quick resection leaving a defined geometry would be advantageous. Therefore, a new minimally invasive resection tool was developed, using rotating foldable cutting edges. This report describes the first experimental in-vitro results of measuring turning moment and forces during cutting of test specimens. Nitinol cutting edges were mounted on a simplified version of the resection instrument. The instrument shaft was combined with an exchangeable gear (1:3.71 vs. 1:5.0), and an exchangeable screw thread for accurate feed motion (0.35 mm or 0.5 mm) was implemented. Furthermore, the option of an added stabilisation body (SB) to prevent strut-torsion during cutting was tested. Tests were performed upon specially designed test specimens, imitating native calcified aortic valves. Resection was successful in all 60 samples (12 samples for each of the five configurations). Mean resection time ranged from 18.7+/-1.0 s (gear 1:3.71, screw thread 0.5, with SB) to 29.3+/-4.6 s (gear 1:5, screw thread 0.35, with SB), mean maximum turning moment ranged from 2.1+/-0.2 Nm (gear 1:3.71, screw thread 0.35, with SB) to 2.8+/-0.4 (gear 1:5, screw thread 0.35, with SB), mean maximum force from 36.0+/-11.3 N (gear 1:3.71, screw thread 0.35, with SB) to 56.3+/-10.5 N (gear 1:3.71, screw thread 0.5, without SB) and mean number of required rotations from 41.3+/-2.9 (gear 1:3.71, screw thread 0.5, with SB) to 59.1+/-3.7 (gear 1:3.71, screw thread 0.35, without SB). In summary, the positive influence of the stabilisation body could be shown. Combining the right parameters, it is possible to limit maximum cutting forces to F(max)<50 N and maximum turning moments to M(max)< 3.0 N.