In vitro testing of a novel cerebral protection device for trans-catheter aortic valve implantation

Aortic Stenosis is the most common valvular heart disease in developed countries. Over the past decade, Transcatheter Aortic Valve Implantation (TAVI) has become increasingly popular thanks to its low invasiveness. However, one of the primary side effects is the release of debris from the native calcified valve while positioning the prosthesis, which may cause cerebrovascular events (CVEs). Because of the risks associated to CVEs, several approaches have been developed to try to reduce this issue, such as the use of cerebral protection devices (CPDs), able to capture and/or deflect particles, impeding their passage in the supra-aortic vessels. In this thesis work, an experimental set-up for the in vitro testing of commercial CPD was developed. The goal was to simulate the debris release during a TAVI procedure and to quantify the particles captured by a commercial CPD and those lost in the systemic and cerebral blood flow, as well as to assess the pressure drop caused by the device. The employed set-up consisted of a simplified mock-up of the human aorta and its main branches. A volumetric pump was used to impose physiological working conditions: a sinusoidal inlet flow rate (mean value: 5 l/min), of which 15% was directed towards the supra-aortic branches. To simulate the debris, soda lime solid glass particles (diameter of 90-106 µm, density of 2.5 g/cm3) were used. Flow and pressure sensors were positioned in the systemic and cerebral circulation, as well as two cartridge filters to capture the lost particles. Physiologic pressure values (80-120 mmHg) were reached after fine tuning the resistance and the compliance of the circuit. Moreover, the branches of the mockup were reduced at their minimum and the connectors were 3D printed as to reduce their internal surface roughness, to minimize the amount of lost particles. Flow and pressure signals were acquired before and after positioning the commercial device and TAVI catheter. The data were then analyzed with MATLAB. The particles captured by the device and by the two filters were weighted and the associated percentages by weight with respect to the total weight of found particles were evaluated. Three sizes of the device were tested (28 mm, 32 mm and 36 mm). For each size, the test was repeated at least 16 times. The results were evaluated in terms of amount of particles captured by the device, by the cerebral filter and the lost particles, as well as the pressure drop caused by the device. The mean values and standard deviations were computed on the first 15 valid tests for each size, obtaining the following results: Particles in the device: Size 28: 66.1%+-8.4%. Size 32: 71.3%+-4.3%. Size 36: 69.3%+-7.1%. Particles in the cerebral filter: Size 28: 2.4%+-1.9%. Size 32: 1.5%+-0.8%. Size 36: 0.7%+-0.5%. Lost particles: Size 28: 0.4%+-5.4%. Size 32: 1.8%+-4.2%. Size 36: 5.2%+-3.1%. Device pressure drop: Size 28: 1.2+-0.2 mmHg. Size 32: 0.7+-0.1 mmHg. Size 36: 0.3+-0.1 mmHg. Seeing that the amount of particles in the cerebral filter is below 3% for all the sizes and that more than 50% is captured by the device, the results highlight the capability of the considered commercial device to deviate and capture the debris released during TAVI procedure. In this regard, it could be a powerful tool for the protection of the cerebral circulation and thus an effective solution to reduce the occurrence of CVEs after TAVI.