Prediction of Suitable Fluoroscopic Implantation Planes for Transcatheter Aortic Valve Implantation in Bicuspid Aortic Valve Anatomy - Clinical Validation of a Novel Approach

Objectives: Treatment of bicuspid aortic valve stenosis (BAV) by transcatheter aortic valve implantation (TAVI) is increasingly performed and shows promising results. Nevertheless, TAVI in BAV is generally considered as more challenging than in regular tricuspid anatomy. One of the underlying reasons can be the difficulty to determine suitable fluoroscopic implantation planes, especially as the regular TAVI approach based on the three cusps' nadirs is not feasible in BAV by definition. We present a method to predict implantation planes by assessment of the preoperative CT scan, and describe its impact on our center's implantations.

Methods: In our approach, the positioning of the TAVI prosthesis in the patient's anatomy is approximated by a vector in the preoperative CT scan. This vector is constructed by the centroid of a polygon that outlines the aorta in the region of the sinotubular junction and, respectively, of the subvalvular LVOT. The 3D coordinates of the two centroids are used to calculate the line of perpendicularity that represents all orthogonal perspectives to the aortic valve's annulus. Verification of the vector can be undertaken by systematic analysis of the resulting orthogonal sectional plane's area that defines the aortic annulus. 58 patients with stenotic BAV (Sievers 0 and I) that were suitable to analyze the method's efficacy underwent TAVI in our institution. Two subgroups were formed according to the technique used for the implantation plane prediction. In group A (n = 26), the plane was determined by experienced operators using different CT-based presumptions and fluoroscopic methods like angiograms or alignment of the crimped valve. In group B, the new approach was used to predict the final implantation plane. After implantation, the solid angle that represents the tilt of the implanted prostheses to the predicted projection was calculated using fluoroscopy. Homoscedasticity of the measurements was confirmed by Levine-test, and Student's t-test was used to determine significance of differences between the means.

Results: The mean solid angle between the fluoroscopic implantation plane and the prosthesis was significantly lower in group B (5.2°, SD = 2.9° versus group A: 11.0°, SD = 5.3°; p < 0.01).

Conclusion: The new method led to a significant reduction of the misalignment between the chosen fluoroscopic projection and the final position of the prosthesis. This might allow more precise valve deployment and improve the procedural outcomes.