Monitoring and evaluation of the surgical Potts shunt physiology using 4-dimensional flow magnetic resonance imaging

Objective: The reversed Potts shunt is an increasingly applied mode of surgical palliation of severe pulmonary hypertension (PH). However, the long-term flow hemodynamic effect of the Potts shunt physiology and desirable long-term hemodynamic end points are not defined. The purpose of this descriptive study was to analyze a series of pediatric patients who underwent surgical Potts shunt as a part of end-stage PH palliation using 4-dimensional (4D)-flow magnetic resonance imaging (MRI) to (1) quantitate the flow through the anastomosis, (2) correlate the shunting pattern with phases of cardiac cycle and PH comorbidities, and (3) describe chronologic changes in shunting pattern. Methods: This was a 2-center study evaluating 4 patients seen in the Pulmonary Hypertension Clinic at Children's Hospital Colorado who were evaluated and selected to undergo surgical reverse Potts shunt at Washington University School of Medicine and were serially followed using comprehensive imaging including cardiac MRI and 4D-flow MRI. Results: After the procedure, each child underwent 2 4D-flow MRI evaluations. Pulmonary pressure offload was evident in all patients, as demonstrated by positive systolic right-to-left flow across the Potts shunt. All patients experienced some degree of the flow reversal, which occurs primarily in diastole. Interventricular dyssynchrony further contributed to flow reversal across the Potts shunt. Lastly, systemic and pulmonary blood mixing in the descending aorta results in secondary helical flow persisting throughout the diastole. Conclusions: 4D-flow MRI demonstrates that children who have undergone a Potts shunt for severe PH can experience shunt flow reversal. Cumulatively, this left-to-right pulmonary shunt adds to right ventricular volume overload. We speculate that a valved conduit may decrease the left to right shunting and improve overall cardiac output.