The present article presents a method for assessing the radial stiffness of nitinol stents. An idealized stent model was created, and its radial stiffness was calculated by means of finite element modeling. The calculations were validated against experimental measurements. The variation of radial stiffness with geometrical dimensions was calculated, and the effect of increasing radial stiffness on endovascular deployment was analyzed. Peak tensile and compressive stresses as well as stent penetration were calculated in the case of an idealized pulmonary artery model having realistic dimensions as well as stiffness. The results of stress calculations were compared with a second set of simulations, where an idealized behavior of the stent (uniform expansion to a theoretical contact diameter) was modeled. The results show how in reality nitinol stents behave in a non-ideal way, having a non-uniform expansion and exerting non-uniform pressure on the contact areas with the artery. Such non-ideality decreases though with the increase in radial stiffness. The radial force alone may be insufficient in describing the stent-artery interaction, and numerical modeling proves to be necessary for capturing such complexity.

Personalised treatment of heart disease requires an understanding of the patient-specific characteristics, which can vary over time. A newly developed implantable surface acoustic wave pressure sensor, capable of continuous monitoring of the left ventricle filling pressure, is a novel device for personalised management of patients with heart disease. However, a one-size-fits-all approach to device sizing will affect its positioning within the pulmonary artery and its relationship to the interrogating device on the chest wall on a patient-specific level. In this paper, we analyse the spatial orientation and morphology of the pulmonary artery and its main branches in patients who could benefit from the device and normal controls. The results could optimise the design of the sensor, its stent, and importantly its placement, ensuring long-term monitoring in patient groups.