EXPERIMENTAL WALL SHEAR ESTIMATION AS A MEANS OF PREDICTING THROMBUS FORMATION WITHIN A 50CC PENN STATE BLOOD PUMP

摘要

The use of ventricular assist devices (VADs) as a means of cardiac support for patients with diminished heart function has been investigated since the 1960s [1]. While VAD therapy has had success in assisting the failing heart, thrombus formation within these devices is one of various complications that still limit its long term use. Research has shown that thrombus deposition in VADs is a function of the underlying fluid mechanics within these devices. Areas of flow stasis, high blood residence time, and wall shear rates under 500 s~(-1) are important flow characteristics driving thrombosis [2]. Particle image velocimetry (PIV) has proven to be a useful flow visualization technique to identify areas in which detrimental flow patterns are likely. In addition to velocity measurements, an estimation of wall shear rate based on experimental PIV studies can help predict thrombus propensity within a Penn State 50cc device. The accuracy of the wall shear rate measurement by PIV is highly dependent on the magnification of the system. Provided particle density is sufficient at near wall locations, we can improve the accuracy of wall shear rate measurements with increased magnification [3]. The outcomes of this study will be compared with similar computational modeling and in vivo studies to better predict thrombus formation within VADs. Clot formation has already been shown to occur along the front bottom edge of the pump in vivo. Previous measurements in this region have reported wall shear rates below 250 s~(-1) suggesting that areas of low wall shear correlate to thrombus formation [4]. Higher magnification PIV allows these regions to be studied in greater detail.