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DOI: 10.1055/s-0036-1571669
Competing Flow between Partial Circulatory Support and Native Cardiac Output: a computational Fluid Dynamics-Study
Objectives: A better understanding of hemodynamic alternations caused by competing blood flows in heart failure patients with partial circulatory support is necessary to optimize effectiveness of treatment. In-vivo flow information is difficult to obtain in this patient group. Computational fluid dynamics (CFD) simulations are an alternative method to gain insight into basic principles of flow phenomena. Circulite Synergy Micro-pump® is such a partial circulatory assist device that connects the left atrium with the right subclavian artery (RSA).
Methods: For 10 patients the lumina of the aorta, supra-aortic vessels and the Circulite outflow cannula were segmented from computed tomography angiographic image data. CFD simulations were performed for a cardiac cycle with constant inflow from the Circulite pump (velocity 1m/s).
Patients were divided into two groups depending on the medial angle of the outflow cannula relative to the RSA (Group1, average angle: 97.89°, n = 6; Group2: 141.62°, n = 4).
Blood flow, velocity magnitude and wall shear stress (WSS) were temporally averaged in the innominate artery (IA) and ascending aorta.
Significant differences in velocity and WSS between groups were assessed with the Student's t-test (significance p< 0.05).
Results: In all 10 cases we found reversed flow in the IA during diastole caused by the Circulite device. In systole the native cardiac output causes antagonizing flow in the IA (and RSA), mostly around the origin of the right carotid artery leading to decreased velocity and WSS (negative correlation to velocity and WSS in the ascending aorta; Pearsońs r -0.898 respectively -0.870).
Comparing the 10 cases depending on their anastomosis angle, the cases with a wider angle showed significantly less antegrade flow from the heart in the IA during systole (shorter time and lower average velocity: 0.084s versus 0.181s and 0.085m/s versus 0.364m/s).
Conclusion: Antagonizing flow from the heart and the Circulite pump in the IA show that effectiveness of this partial support device is not optimal yet. Synchronizing the device with the cardiac cycle could be one way to increase effectiveness of future partial support devices.
Fig. 1 Velocity in Innominate artery. Colour coded representation of superior-inferior velocity in innominate artery (arrows) in peak systole (black line in diagram), left for Group 1 (perpendicular angle; red in inset); right for Group 2 (wide angle; red in inset); middle: graph of velocity in the innominate artery over the whole cardiac cycle (average of each group) (positive velocity values indicate flow from the heart to the periphery) showing higher velocity in Group 1 (left) in systole.