Artery in Microgravity: an in vitro set-up to characterize stented and stenosed coronary artery hemodynamics in space missions

The presented thesis work can be divided into two parts: in the first part the Coronary Artery Simulator of BDC Labs is characterized together with PD-0500 Pump and PD-1100 Pump, while in the second part AIM project is described. In addition to in vivo and in silico analyses, in vitro experiments are becoming increasingly important, since they allow to perform measurements that can not be implemented in vivo because of their invasivity. Several in vitro set-ups have been developed, to simulate both physiological or pathological human blood circulation, by varying loop parameters. They also allow to directly examine the behaviour of cardiovascular devices before their implant in patient’s body, such as prosthetic valves and stents, and they constitute an important tool for surgeon’s training. One of the main producers of mock circulatory loop is BDC Laboratories and the analyses are performed on its Coronary Artery Simulated Use Solution, that provides a platform to evaluate coronary intervention procedures for intravascular interventions. The aim of this part of the study is to evaluate pressures under a specific pathological situation: atherosclerosis. In fact, this is the leading cause of cardiovascular disease. Since it causes asymmetric focal thickening of the innermost layer of arteries, thus narrowing the lumen, the realization of several obstructions is performed, to characterize the mechanical behaviour of the loop. The relationship between pressure drops and flow rates is investigated, to evaluate an analytical expression for pressure gradients. Then, hydraulic resistance of the MCL is established. In the second part of the study, the Artery In Microgravity (AIM) project is described. The project is being developed by an international group of students from Politecnico di Torino and ISAE-SUPAERO. It is the first experiment to be selected for the “Orbit Your Thesis!” programme of ESA Academy and it is a 2U experiment cube designed for the ICE Cubes facility on board of the International Space Station. The experiment is expected to be launched on SpaceX-20 in 2020. In view of the impact that coronary artery disease has on humans, as well as of the increasing number of people that will be involved in space flights in the future and of the influence of the absence of gravity in astronauts’ haemodynamic, the presence of stenosis or of stenting needs to be investigated in depth. In addition, as most stents are metallic objects, the radiation exposure in space might interact with their surface. Therefore, the aim of AIM is to start studying the vascular haemodynamics in a stented and a stenosed coronary artery on Earth and in microgravity and the stent-radiation coupling. This will allow to learn about the effect gravity plays on coronary artery haemodynamics, the effects of microgravity and radiation on the performance of implantable devices and ultimately the risks of myocardial infarction to astronauts on long-distance spaceflight. The experimental setup consists of a closed hydraulic loop containing two models of a coronary artery in series (a stented phantom and a stenosed one). The pressure of the fluid will be studied along its path using pressure sensors and a camera will visualise the flow. The same experiments will be repeated on the ground with the same conditions as the in-flight model for comparison. The full data and results will be available after the completion of the mission, which is expected to be in late 2020.