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Novel Mitral Annuloplasty Ring Sizer Accurately Forecasts Changes In Leaflet Coaptation Length: Validation In Cadaveric Swine Heart Model
NIKOLA DOBRILOVIC.
NorthShore University Hospital System, Chicago, IL, USA.
BackgroundThe current method for mitral annuloplasty ring sizing has remained essentially unchanged for a half century and offers surgeons limited actionable information.
Methods
Cadaveric swine hearts (n=20) were used to validate the novel sizing device/method. We hypothesized that the paired-ring sizer will force annuloplasty sutures to conform to its exact shape, and, therefore, accurately predict changes in coaptation length (when used to “downsize” the mitral annulus). Anterior leaflet coaptation length was measured under conditions of left ventricular saline distention. Coaptation length measurements were collected 1) at baseline, 2) with the sizer in place temporarily holding sutures in position (figure), and 3) after final implantation of a (corresponding size) Physio-2 ring. "Predicted" (sizer) and "actual" (implanted Physio-2 ring) coaptation lengths were compared using Bland-Altman analysis to assess accuracy.
Results
In nineteen hearts a moderate increase in coaptation length was achieved (2.0-5.5 mm), and in one heart no change could be demonstrated (heart was too small). The mean increase in coaptation length was 3.7 mm. The initial, "predicted" (sizer) coaptation lengths corresponded well (≤0.5 mm difference) with the final, "actual" (implanted ring) coaptation lengths in all 20 hearts (table). The mean difference between the predicted and actual coaptation lengths (absolute numbers) was 0.175 mm.
[Statistics: The mean difference [95% CI] between predicted and actual sizes indicated that predicted measurements were slightly higher than actual (0.08 [-0.06, 0.21)], but not different than zero. Limits of agreement were from -0.50 to 0.65. There did not appear to be significant heteroscedasticity (table/graph).]
Conclusion
Accuracy of a novel mitral annuloplasty ring sizing device was validated using a cadaveric swine heart model. The coaptation length initially predicted by the sizer corresponded accurately with the coaptation length observed upon implantation of a corresponding commercially available ring. This device and method can be designed to function with any commercially available annuloplasty product (mitral/tricuspid, ring/band, all shapes/brands). Continued development of this technology should provide surgeons with precise control over the final coaptation length by previewing several different rings prior to committing to a final implant. This device has recently been approved for human trial at our institution.
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