A new tool for the resection of aortic valves: In-vitro results for turning moments and forces using Nitinol cutting edges

Abstract

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.

Patient-specific modeling of biomechanical interaction in transcatheter aortic valve deployment

“…Whether these leaflets have any mechanical impact on the TAV intervention is currently unclear. It has been suggested that these calcified leaflets be removed prior to the TAV intervention by a separate minimally invasive means 37 . Our simulation results showed that high stress concentrations (Table 2) were seen around the calcified regions in the leaflets as well as at the attachment lines of leaflets and the aortic sinuses.…”

Fluid Dynamic Investigation of the ATS 3F Enable Sutureless Heart Valve

“…5,6 These surgical alternative options may be potentially incorporated into routine AVR programs in the foreseeable future as a capable treatment option for mid-or low-risk groups. By the use of sutureless heart valves (SHV) and other innovative tools, 7 a new field in heart surgery with less invasiveness and implantation time may improve outcomes for patients and potential cost reduction.…”