Transcatheter Aortic Valve Replacement: optimisation of the technique and future challenges

Transcatheter aortic valve replacement is an accepted alternative treatment for severe symptomatic aortic valve replacement in inoperable patients or patients at high surgical risk. Large randomized clinical trials have proved non-inferiority and even superiority of TAVR compared to surgical aortic valve replacement in terms of one-year survival in this group of patients.
After its first introduction in 2002, several technical improvements in the past few years have enhanced the feasibility and the results of TAVR procedures. In addition to technical improvements, increased experience with the technique and introduction of several modern imaging modalities have facilitated easier and safer procedures. Imaging modalities are important in the workup procedure of TAVR, especially for patient selection and planning of the procedure. Accurate positioning of the valve prosthesis in the native aortic valve annulus is a critical step during TAVR procedure in order to prevent important complications such as prosthesis migration, coronary artery obstruction and significant paravalvular regurgitation. As discussed in the present thesis, both multislice computed tomography and the DynaCT technique are able to adequately determine the optimal fluoroscopic views for accurate prosthesis positioning.
Although TAVR is a promising technique, which improves survival and quality of life in a large group of patients, its broad implementation is however hampered by a relatively high rate of complications. Among others, post-TAVR paravalvular aortic valve regurgitation (PAR) and ischemic cerebral injury related to TAVR are important post-TAVR complications. As reported in this thesis, an important predictor of post-TAVR PAR is aortic valve calcification. Furthermore we discussed that significant PAR can be prevented by a precise prosthesis sizing, an adequate prosthesis positioning, and a clever prosthesis design.
Cerebral ischemic injury is another important complication after TAVR with apparent cerebral infarction having a relatively low incidence. However, clinically silent brain infarctions are reported in up to 100% of cases after TAVR. These silent brain infarctions may cause neurocognitive decline on a long term after TAVR. In this thesis we found an independent association between age, hyperlipidaemia at baseline and balloon post-dilatation and the number of post-TAVR ischemic brain lesions. Only peak transaortic gradient was independently associated with post-procedural total infarct volume. Expansion of the understanding of neurological injury associated with TAVR has fuelled the interest in strategies for their prevention. Recently, much effort was put into the use of dedicated embolic protection devices (EPD) for cerebral protection during TAVR. Several types of EPD, either deflecting of capturing embolic particles, have been subject of research in the past years. The results of pilot studies investigating the use of a few of these EPD devices are discussed in this thesis. Our data have shown considerable promise for the embolic deflection devices, the Embrella and the Keystone heart deflection devices, at least in terms of reduction of post-procedural cerebral ischemic volume. Hence, further refinements to EPD technique may offer a modality for significant reduction of brain injury during TAVR. In addition, adequately powered and randomized controlled trials, implementing competent neurocognitive tests, are needed to investigate the benefit of EPD-usage during TAVR.