People over the age of sixty-five are most commonly affected by aortic stenosis (AS), a common heart valve disease. Transcatheter aortic valve implantation (TAVI) is a minimally invasive treatment for AS that replaces the function of the diseased native valve with a prosthetic device that relies on balloon catheters for device implantation. According to current clinical guidelines, the choice of the implantable device is based on preoperative sizing measurement by image-based technology. However, this assessment has inherent limitations that can lead to the selection of a sub-optimal prosthesis size, which in turn can lead to significant intra-operative complications such as aortic regurgitation or electrical signal disturbances in the heart.

Using balloon pressure and volume data, this paper proposes an intra-operative method for determining the size of the aortic annulus, taking into account its compliance and elliptical geometries. Intra-balloon pressure-volume curves were obtained using an inflation device operating a commercially available valvuloplasty balloon catheter. A sizing algorithm for the estimation of annulus dimensions was integrated via a characterised analytical model and a numerical model for balloon free-inflation.

Experiments were performed on circular and elliptical idealized aortic phantoms. Experimental results show that the pressure-volume data processed by the sizing algorithm can be used to determine the circular annulus diameter for all tissue stiffnesses. The measurement of stiffer elliptical annulus phantoms shows good precision and high repeatability. This work represents a significant step forward in improving the selection of TAVI devices by sizing the compliant aortic annulus with complex geometry using balloon catheters.