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Cavopulmonary Assist Using a Percutaneous, Bi-conical, Single Impeller Pump: a New Spin for Fontan Circulatory Support
Mark D. Rodefeld1, Brandon Coats2, Travis Fisher2, John Brown1, Steve Frankel2; 1Department of Surgery, Indiana University School of Medicine, Indianapolis, IN; 2Purdue University Department of Mechanical Engineering, West Lafayette, IN
READER COMMENTS
Objective: In a univentricular Fontan circulation, a delicate balance exists between the systemic venous and pulmonary arterial circulations. Modest augmentation (2-5 mmHg) of existing cavopulmonary flow would reduce systemic venous pressure, improve ventricular filling, and substantially improve hemodynamic status. A reasonable means of providing high-volume, low-pressure flow in this unique situation does not exist. We hypothesized that an expandable single impeller pump, based on the von Karman viscous pump principle, is ideal for this function.
Methods: A 3-dimensional computational fluid dynamics (CFD) model of the total cavopulmonary connection (TCPC) was created. The impeller was represented by an actuator disk (a 2-sided conical disk) positioned in the center of the TCPC intersection with rotation in the vena caval axis. Flow was modeled under 3 conditions: 1) passive flow with no disc present; 2) passive flow with a non-rotating disk, and 3) flow with a rotating disc (1K, 5K, and 10K rpm). Flow patterns, pressure gradient, and flow rate were estimated for each case. In vitro performance of a flexible 2-sided conical disk impeller and protective cage was assessed by measuring pressure rise and induced flow rate at 5K, 10K, and 15K rpm.
Results: The presence of an actuator disc alone (nonrotating) stabilizes TCPC flow patterns and offsets the hydraulic energy loss which occurs when no disk is present at all. Disk rotation (5K, 10K, and 15K rpm) from a dynamic flow of 4.4 L/min (adult Fontan cardiac output) induced significant flow increases (1.1, 1.7, and 1.9 L/min) with a pressure differential of 1.4, 1.8, and 2.0 mmHg across the TCPC. In vitro videography confirms bidirectional inflow and outflow augmentation. Experimental flow rates correlate closely to CFD predictions.
Conclusion: A simple percutaneous rotary pump, comprised of a single expandable bi-conical disk impeller and protective cage, is ideal to provide cavopulmonary assist. With a single impeller, flow is augmented in all 4 axes, in the ideal pressure range, with no venous pathway obstruction. It can apply to both the 3-way “ T ” (bidirectional Glenn) and the 4-way “ + ” (TCPC) conditions. In patients with established univentricular Fontan circulations, this provides a previously unavailable bridge-to-recovery or -transplant option. It can also provide temporary perioperative support and enable compression of univentricular palliative procedures at any stage by substantially improving physiologic status after Fontan conversion.


Cavopulmonary assist
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