Poster T14 - The Impact of Simple Surface Geometry Design Alterations on Impella Sheath Flow Dynamics

Introduction: Mechanical circulatory support (MCS) devices are used to maintain blood flow in cases of severe heart failure and complex percutaneous coronary intervention (PCI). Impella, a commonly used MCS device developed by Abiomed Inc., requires large-bore femoral access which can result in complications including limb ischemia. Altering surface geometry of the introducer sheath may improve blood flow to the lower extremity, mitigating these complications and improving patient outcomes.

Materials and

Methods: A replica of the Abiomed 14 French Impella control sheath was reproduced using computer-aided design (CAD) software and a 3D printer. Five novel 14 French sheaths were then designed with continuous surface volume cutouts to create channels of varying profiles and quantities. The designs included a narrow single channel, narrow double channel, narrow triple channel, wide single channel, and wide double channel sheath. A testing apparatus was built using a pump, power source, Arduino Uno, latex tubing, and hall effect fluid flow sensors proximal, distal, and in parallel with a simulated arteriotomy insertion point simulated using ballistic gel (Figure 1). Water was used to simulate blood. The flow at each point was measured for every sheath. A linear regression analysis was performed to analyze the correlation between flow rate and independent variables including cutout volume (VC), surface area of the sheath (SA), and number of channels (NC).

Results, Conclusions, and Discussions: Results
The cutout volumes (CV) of the narrow single channel, narrow double channel, narrow triple channel, wide single channel, and wide double channel sheath were 35.99 mm3, 71.50 mm3, 106.91 mm3, 59.75 mm3, and 106.81mm3 respectively. The testing rig produced a mean proximal flow of 710 ±6 ml/min (CI 95%). Flow distal to the replica or control sheath was 192 ml/min. The flow distal to the narrow single channel, narrow double channel, narrow triple channel, wide single channel, and wide double channel sheath was 179 ml/min, 238 ml/min, 275 ml/min, 226 ml/min, and 207 ml/min respectively (Figure 2). The coefficients for the fitted regression model were 0.49 ( p=0.000) for VC, 0.02 for SA (p= 0.71), -3.4 for NC (p= 0.61) . The R-squared value was 0.63 and standard error was 28.2.
Conclusion
Alterations of Impella sheath surface geometry demonstrated measurable differences in fluid flow distal to the sheaths. Statistically, cutout volume was the only identified factor that affected flow rate distal to the simulated arteriotomy. Larger volume cutouts resulted in more flow preservation. The surface area of the cutout and the number of channels did not influence the flow rate.
As expected, the single wide channel outperformed the single narrow channel. However, interestingly, the double narrow channel surpassed the double wide channel in flow rate performance, suggesting that other aspects may influence flow rate outside of cutout volume alone.
Discussion
Simple alterations to the surface geometry of the Impella sheath may one day lead to a reduction in serious complications associated with this often life-saving tool, including that of critical limb ischemia. Further research is necessary to determine the ideal surface geometry for preservation of flow distal to the arteriotomy and into the lower extremity.

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