Adding Annuloplasty Ring to Remodeling Aortic Valve Sparing Repair is Equal to Reimplantation Technique - Insights from in vitro Stress-Strain Characterization
Troels Lading1, Thomas Lindskow1, Tommy Bechsgaard1, Diana M. R°pcke1, Peter Johansen2, Sten L. Nielsen1.
1Department of Cardiothoracic and Vascular Surgery, Aarhus University Hospital, Aarhus N, Denmark, 2Department of Engineering, Faculty of Science and Technology, Aarhus University, Aarhus, Denmark.
OBJECTIVE: In recent years, it has been proposed to add an annuloplasty ring to the remodeling aortic valve sparing technique in order to reproduce the annular stabilization as seen in reimplantation technique. The objective of this in vitro study was to evaluate the biomechanical properties of the two repair techniques with and without an annuloplasty ring.
METHODS: Thirty porcine roots from pigs with a bodyweight of 80 kilograms have been randomized to either no repair (n=6), no repair with an annular ring (n=6), remodeling (n=6), remodeling with an annular ring (n=6) or reimplantation (n=6). For the experiments, a pulsatile in vitro setup was used. For measurements of the force distribution a transducer has been developed. The force transducer is based on strain gauges and is capable of measuring inward and outward distension of the aortic annulus.
RESULTS: Analysis of the force distribution in newton (N) showed a clear temporal correlation to aortic pressure and flow. The reimplantation technique had a significantly lower outward cyclic force amplitude during heart cycle compared to the remodeling technique (0.5 ▒ 0.3 N vs 1.5 ▒ 0.6 N, p = 0.001). The reimplantation technique had a significantly lower minimum force in diastole compared to the remodeling technique (0.7 ▒ 0.4 N vs 1.6 ▒ 0.9 N, p = 0.01). Interestingly, remodeling with ring mimicked the force distribution in the reimplantation group, with low minimum force in diastole of 0.5 ▒ 0.3 N, and lower cyclic force amplitude of 0.6 ▒ 0.2 N. Both groups were significantly different from remodeling group without ring.
CONCLUSIONS: The force distribution after reimplantation and remodeling with ring had a significantly higher level of stabilization in the aortic annulus compared to the remodeling without ring, indicated by a lower minimum force in diastole and a dampening of cyclic force dynamic through heart cycle. This in vitro study indicates that an annuloplasty ring when used with the remodeling technique provide similar stabilizing properties as the reimplantation technique.
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