[In Vitro Experimental Study on Hemodynamics of Transcatheter Aortic Valve Replacement]

The patient-specific aortic silicone model was established based on CTA data. The digital particle image velocimetry (DPIV) test method in the modified ViVitro pulsatile flow system was used to investigate the aortic hemodynamic performance and flow field characteristics before and after transcatheter aortic valve replacement (TAVR). The results showed that the hemodynamic parameters were consistent with the clinical data, which verified the accuracy of the model. From the comparative study of preoperative and postoperative effective orifice area (0.33 cm2 and 1.78 cm2), mean pressure difference (58 mmHg and 9 mmHg), percentage of regurgitation (52% and 8%), peak flow velocity (4.60 m/s and 1.81 m/s) and flow field distribution (eccentric jet and uniform jet), the immediate efficacy after TAVR is good. From the perspective of viscous shear stress and Reynolds shear stress, the risk of hemolysis and thrombotic problems was low in preoperative and postoperative patient-specific models. This study provides a set of reliable DPIV testing methods for aortic flow field, and provides biomechanical basis for the immediate and long-term effectiveness of TAVR from the perspective of hemodynamics and flow field characteristics. It has important application value in clinical diagnosis, surgical treatment and long-term evaluation.

Microscale imaging of cilia-driven fluid flow

Cilia-driven fluid flow is important for multiple processes in the body, including respiratory mucus clearance, gamete transport in the oviduct, right-left patterning in the embryonic node, and cerebrospinal fluid circulation. Multiple imaging techniques have been applied toward quantifying ciliary flow. Here, we review common velocimetry methods of quantifying fluid flow. We then discuss four important optical modalities, including light microscopy, epifluorescence, confocal microscopy, and optical coherence tomography, that have been used to investigate cilia-driven flow.