We demonstrate a multislice computed tomography (MSCT)-based method to calculate the prediction of the so-called ‘line of perpendicularity’ (LOP) and the ‘implanter's views’ (IVs) for transcatheter aortic valve implantation (TAVI) procedures. The LOP represents all possible angiographic angulations that result in an orthogonal view to the aortic annulus plane. The IVs allow visual confirmation of correct implantation planes, and are crucial for the commissural aligned implantation of second-generation TAVI prostheses.METHODS
The LOP and IVs of 335 concomitant patients were prospectively analysed using multiple plane reconstruction (MPR) of the patient's MSCT scans. Exclusion criteria were bicuspid valves (n = 18) and valve-in-valve TAVI (n = 15). In the MPRs, the aortic cusps' lowest points were marked. With the marker's three-dimensional coordinates, the graph of the LOP with the IVs was calculated and plotted using vector mathematics. In the last 244 cases, the IV with the right coronary cusp in front was chosen for the first aortic root angiogram of the TAVI procedure. The finally used angulation was confirmed by aortic angiogram prior to the valve implantation. Solid angle differences that show the combined left anterior oblique/right anterior oblique and cranio/caudal movement of the C-arm allow quantification of corrections as well as demonstrate interindividual variations.RESULTS
There is a broad interindividual variation of the aortic valve's topology with solid angle variations of up to 74°. The shape of the LOPs is extremely varying, especially regarding the slope of the curve that indicates differences in valve orientations. Among the 244 patients for whom we used the prediction for the procedure, the first angiogram was considered perfect for implantation without further corrections in 97% (n = 237) of them. In case of the 7 patients with subsequent corrections, the mean solid angle between the prediction and the final angiogram prior to implantation was 6.2° (±5°); the largest correction was 14°.CONCLUSIONS
Prediction of the implantation plane by analysing the patient's MSCT is highly reliable in achieving an adequate view of the aortic annulus in TAVI. The analysis of LOPs showed the large interindividual differences that permit using a standard implantation plane. Therefore, we strongly recommend determining the LOP and IVs during the patient's screening process in each single TAVI case.