Ventricular assist devices

Thoracic and abdominal devices radiologists should recognize: pictorial review

OBJECTIVE

Surgical, interventional, and diagnostic devices are continually being developed and often have unexpected radiographic appearances. The purpose of this article is to familiarize the radiologist with several devices that may be placed in the thorax and abdomen.

CONCLUSION

The radiologist's familiarity with the radiographic appearance of devices placed in the chest and abdomen is essential for accurate image interpretation and identification of postprocedure complications.

Flow simulation of a diaphragm-type ventricular assist device with structural interactions

A numerical simulation of the fluid and structure interactions was performed for a diaphragm-type Ventricular Assist Device (VAD). The simulation was included two incompressible fluids and three elastic solid regions. The detailed information of both fluid and solid dynamic are crucial to evaluate the performance of the device. Localization of potential points prone to hemolysis and thrombus formation and disturbed flow with creation of recirculation zones are vary important. Here, the HeartSaver VAD was modeled as a two dimensional chambers with an inlet and an outlet elastic valves, an elastic sac-shape membrane, driving fluid and blood. A pulsatile velocity condition was applied at the inlet of the driving fluid chamber. As the results, the flow characteristics affecting the blood cells including velocity, pressure, wall shear stress and the elastic valves operation were presented in details.

Three-dimensional magnetic resonance flow analysis in a ventricular assist device

OBJECTIVE

The assessment of flow characteristics inside ventricular assist devices by magnetic resonance imaging techniques may provide insight into the mechanisms underlying the high rate of thromboembolic events after implantation of a ventricular assist device. Furthermore, these investigations may form the basis to optimize the device's design and its need for anticoagulation. The purpose of this study was to integrate a clinical routine ventricular assist device into a flow circuit with realistic geometric and pulsatile inflow conditions. Combination with flow-sensitive magnetic resonance imaging at 3 T permitted the detailed analysis of local and global 3-dimensional flow dynamics in a realistic environment.

METHODS

A commercially available ventricular assist device was integrated into a magnetic resonance-compatible flow circuit. Flow-sensitive 3-dimensional magnetic resonance imaging was performed to measure time-resolved 3-directional flow velocities in the entire device. Advanced computer-aided 3-dimensional flow visualization methods were used to derive a comprehensive picture of flow dynamics within the ventricular assist device system.

RESULTS

On the basis of the ventricular assist device model system, magnetic resonance imaging, and flow visualization, the first 4-dimensional functional magnetic resonance imaging analysis of flow characteristics inside an operating clinical routine ventricular assist device chamber system is reported. Detailed visualization of flow patterns and local changes in flow characteristics were successfully performed and revealed locally accelerated, vortical, and helical flow regions inside the geometry of the device.

CONCLUSIONS

Complex flow patterns such as vortex formation and locally accelerated flow demonstrate the potential of the presented method to further deepen the understanding of complex and regionally different flow characteristics inside ventricular assist devices.