No abstract

Heart failure continues to be a major global health problem causing significant health issues and deaths. Left Ventricular Assist Device (LVAD) was developed as an alternative to heart transplant to support the patients with severe end stage heart failure. Despite the current advancement of LVAD, constant improvements are always being made in making it smaller LVADs tailored for patients with smaller physiology while still maintaining the flow ventricular pump capability to the body. This study evaluated the effect of using a smaller sized LVAD using Computation Fluid Dynamics (CFD) and compared with the initial pump size at their respective designed rotating speed. Two model variants were studied, the initial design with 44.8mm diameter impeller (2000 rpm rotating speed) and the smaller 37.0 mm diameter impeller (2500 rpm rotating speed). These designs were compared by their key criteria mechanical performances particularly the produced pressure difference along a range of flowrate and the efficiency curve. At the required flowrate of 5 L/min, the smaller sized 37.0 mm impeller was able to deliver the flowrate at a slightly higher pressure difference of 114.60 mmHg as compared to the 44.8 mm impeller at 106.01 mmHg. In overall, both model variant produced similar pressure-flowrate curve with the 37.0 mm impeller performing marginally better at higher flowrates. Efficiency was able to be maintained at 49-60 percent despite being a smaller impeller at a faster rotating speed. Miniaturizing the LVAD has been numerically demonstrated to be feasible to produce the needed flow output at the required pressure difference without affect efficiency significantly .

Spiral flow-inducing cannula has been shown in previous research to exhibit a considerable effect on flow hemodynamic. However, there is still room for improvement. In this study, several design variations were tested to determine which variants were the best in terms of flow reduction. Computational Fluid Dynamics (CFD) software was used to simulate flow within a spiral flow-inducing cannula with several variations from chamber width and angle differences. The variants were compared against each other by using several flow parameters and a selection method was employed to determine which model was the best. It was found that a variant that has the widest chamber (14 mm) and biggest angle opening (70°) from the chamber to the cannula tube was the best in several parameters, and as such was chosen as the best variant. When compared with the standard straight cannula, the reduction in flow output was recorded to be 30% which is deemed significantly. In conclusion, spiral flow cannula recorded better hemodynamic effects with lower outflow velocity and wall shear stress value.

The rise of heart failure in the setting of shortage heart donor had brought to the emergence of development of left ventricular assist device (LVAD). However, patients are still encountering severe complications such as stroke and device thrombosis due to the hemodynamic changes. This study aimed to compare the hemodynamic characteristic between the standard and spiral LVAD outflow cannula. Two different anastomosis sites (2cm and 3cm) from sino-tubular junction are used and a spiral inducing chamber is attached to the cannula to promote spiral flow. The result showed that spiral LVAD cannula exhibit a lower output velocity with 37% percentage difference and lower region of low WSS value.