Aortic root sizing for transcatheter aortic valve implantation using a shape model parameterisation.

During a transcatheter aortic valve implantation, an axisymmetric implant is placed in an irregularly shaped aortic root. Implanting an incorrect size can cause complications such as leakage of blood alongside or through the implant. The aim of this study was to construct a method that determines the optimal size of the implant based on the three-dimensional shape of the aortic root. Based on the pre-interventional computed tomography scan of 89 patients, a statistical shape model of their aortic root was constructed. The weights associated with the principal components and the volume of calcification in the aortic valve were used as parameters in a classification algorithm. The classification algorithm was trained using the patients with no or mild leakage after their intervention. Subsequently, the algorithms were applied to the patients with moderate to severe leakage. Cross validation showed that a random forest classifier assigned the same size in 65 ± 7% of the training cases, while 57 ± 8% of the patients with moderate to severe leakage were assigned a different size. This initial study showed that this semi-automatic method has the potential to correctly assign an implant size. Further research is required to assess whether the different size implants would improve the outcome of those patients.

Morphological Characteristics and Calcification of the Native Aortic Valve and the Relation to Significant Aortic Regurgitation after CoreValve TAVI.

BACKGROUND AND AIM OF THE STUDY: Aortic regurgitation (AR) is a frequent and life-limiting complication after transcatheter aortic valve implantation (TAVI). The study aim was to relate post-TAVI AR, using a self-expandable stent, to detailed baseline anatomical and morphological characteristics of the native aortic valve. METHODS: A total of 82 patients (40 males, 42 females; mean age 80 ± 7 years) who received a Medtronic CoreValve implant was included. Aortic root morphology, aortic annulus and implant size mismatch, implant position, extent of aortic annulus and leaflet calcification, the connected sub-annular calcification volume, and their distribution were quantified based on computed tomography scan analysis. AR following TAVI was quantified using standardized angiography and echocardiography. RESULTS: The mean logistic EuroSCORE of all patients was 16.9 ± 11.1%. According to angiography and echocardiography, 41% and 39% respectively, of the patients had AR grade ≥2. The two methods correlated moderately (Spearman's ρ = 0.51, p <0.001). The maximal diameter of the native annulus was larger in patients with significant AR after TAVI based on echocardiography (28.0 mm versus 26.8 mm, p = 0.059). Excessive calcification, especially on the left coronary cusp, was present in patients with significant AR, based on angiography (AR ≥II 71.0 mm3 versus AR

A validated methodology for patient specific computational modeling of self-expandable transcatheter aortic valve implantation.

Leakage of blood alongside the implant is a relatively frequent and life-limiting complication after transcatheter aortic valve implantation. The aim of this study is to develop and validate a workflow to simulate the implantation prior to the intervention. Based on the simulation outcome, the amount of leakage is estimated in order to evaluate the risk of a severe complication. A finite element model of the stent implantation in 10 patients was created based on a pre-operative computed tomography scan. All 10 patients also received a follow-up computed tomography scan, after the implantation. This scan was used to extract the deformed geometry of the stent and the position of the calcifications for validation of the simulation results. The maximal average perimeter difference between the simulated stent and the post-operative stent is 2.9±2.1mm, and occurs at the bottom of the device. The sensitivity of the simulation to the soft tissue material parameters and aortic root wall thickness was tested. The maximal diameter deviation of 6% occurred when the thickness of the aortic root was doubled. The result of the leakage analysis based on the distance between the simulated stent and the surrounding aortic root corresponded well when no regurgitation was observed. The developed tools have the potential to reduce the occurrence and severity of leakage by providing the clinician with additional information prior to the intervention. The simulated geometry and estimated leakage can help decide on the best implant type, size and position before treatment.

Patient-specific image-based computer simulation for theprediction of valve morphology and calcium displacement after TAVI with the Medtronic CoreValve and the Edwards SAPIEN valve.

AIMS: Our aim was to validate patient-specific software integrating baseline anatomy and biomechanical properties of both the aortic root and valve for the prediction of valve morphology and aortic leaflet calcium displacement after TAVI. METHODS AND RESULTS: Finite element computer modelling was performed in 39 patients treated with a Medtronic CoreValve System (MCS; n=33) or an Edwards SAPIEN XT (ESV; n=6). Quantitative axial frame morphology at inflow (MCS, ESV) and nadir, coaptation and commissures (MCS) was compared between multislice computed tomography (MSCT) post TAVI and a computer model as well as displacement of the aortic leaflet calcifications, quantified by the distance between the coronary ostium and the closest calcium nodule. Bland-Altman analysis revealed a strong correlation between the observed (MSCT) and predicted frame dimensions, although small differences were detected for, e.g., Dmin at the inflow (mean±SD MSCT vs. MODEL: 21.6±2.4 mm vs. 22.0±2.4 mm; difference±SD: -0.4±1.3 mm, p<0.05) and Dmax (25.6±2.7 mm vs. 26.2±2.7 mm; difference±SD: -0.6±1.0 mm, p<0.01). The observed and predicted calcium displacements were highly correlated for the left and right coronary ostia (R2=0.67 and R2=0.71, respectively p<0.001). CONCLUSIONS: Dedicated software allows accurate prediction of frame morphology and calcium displacement after valve implantation, which may help to improve outcome.