Development of an in vitro setup for the assessment of embolic protection devices during Transcatheter Aortic Valve Implantation

More than 40 million people are living with either mitral or aortic valve disease worldwide, and more than 180 000 heart valve replacement surgeries are performed each year in the US. During the last 15 years, the Transcatheter Aortic Valve Implant (TAVI) has become a viable alternative to aortic valve surgery in symptomatic patients with severe aortic stenosis, since it reduces the complications and risks related to the open-heart traditional procedure and the post-operative recovery period. However, during TAVI procedure, the native valve is compressed with the consequent release of calcifications in the form of micro-emboli, that, if they enter in the cerebral circulation, can cause the so called Cerebrovascular Events, meaning thrombotic phenomena, ischemic phenomena, and stroke. To avoid this, Cerebral Protection Devices (CPDs) have been introduced. These are designed to capture the released debris and/or deflect them into the systemic bloodstream. The goal of the proposed thesis is to develop an experimental set-up with the purpose of testing a CPD in terms of amount of particles that the device could retain. A mock-up including the supra-aortic branches, the iliac arteries, the aortic arch, and the ascending and descending aorta tracts was used for the tests. The tests were carried out under physiological working conditions, imposing a sinusoidal inlet flow rate through a volumetric pump with a mean value of about 5 l/min. Flow rate and pressures were monitored using one flow meter at the inlet of the mockup and a second one at the supra-aortic branches and pressure sensors. Soda lime solid glass particles (diameter of 90-106 µm, density of 2.5 g/cm3) were injected at the inlet to simulate the released debris. Downstream of the iliac arteries and supra-aortic branches, two cartridge filters with 50 μm porosity were placed to capture the particles that go into the systemic circulation and the ones into the cerebral circulation. The hydraulic circuit was fine tuned to maintain pressures within the physiological range (80-120 mmHg), by means of resistance valves and compliance chamber. The hydraulic circuit was designed in such a way as to reduce at minimum the amount of particles lost in the circuit. To do so, tubes length and mockup branches were limited, and the used connectors were 3D printed with limited internal surface roughness. Three device sizes (diameter of 28 mm, 32 mm, 36mm) were examined, and a total of 15 valid trials were conducted for each size and a final 16th trial with full retrieve of the device. The results are as percentage of the injected particles are: •??Lost particles: Size 28: 0.4%±5.4%. Size 32: 1.8%±4.2%. Size 36: 5.2%±3.1% •??Particles in the cerebral filter: Size 28: 2.4%±1.9%. Size 32: 1.5%±0.8%. Size 36: 0.7%±0.5% •??Particles captured by the device: Size 28: 66.1%±8.4%. Size 32: 71.3%±4.3%. Size 36: 69.3%±7.1% •??Pressure drop due to the device: Size 28: 1.23mmHg±0.23mmHg. Size 32: 0.68 mmHg±0.10mmHg. Size 36: 0.30 mmHg±0.14 mmHg. The obtained results allow to assess that the commercial device does reduce the quantity of particles that go towards the cerebral circulation and it does not generate an excessive pressure drop when implanted, avoiding possible complications for the patient’s heart during the TAVI procedure. This makes it a valuable option as Cerebral Protection Device to be used during transcatheter aortic valve replacement.