Close look at the Potts shunt flow hemodynamics in a patient with severe pulmonary hypertension: 4D‐flow MRI evaluation

Abstract

Surgical or interventional creation of an anastomosis between the left pulmonary artery and the descending aorta, commonly known as the Potts shunt, was originally described as a method of supplementing pulmonary blood flow in infants with congenital heart disease in the spectrum of tetralogy of Fallot. It also represents a therapeutic option for endstage pulmonary arterial hypertension (PAH). The Potts shunt immediately produces a decrease in the pressure difference between the supra-systemic right ventricle (RV) and the systemic circulation, which is a characteristic finding in severe PAH. The baseline reduction in RV afterload is accompanied by facilitating maintenance of cardiac output during intermittent spikes in pulmonary vascular resistance (PVR). The physical position of the anastomosis in the descending aorta relatively spares coronary and cerebral oxygen delivery while improving lower body perfusion, albeit with desaturated blood. However, under conditions when the pulmonary arterial pressure falls below systemic pressures, there is a risk of reversing the direction of blood flow through the anastomosis, creating a left-to-right shunt, which could be deleterious to the pulmonary circulation by volume loading the pulmonary arterial bed. Consequently, intermittent assessment of flow direction and patterns through the Potts anastomosis may guide treatment decisions. Fourdimensional flow magnetic resonance imaging (4D-Flow MRI) permits comprehensive 3D coverage and quantification of time-resolved 3D blood flow in a target circulation. Unlike conventional Doppler echocardiography and 2D phase contrast MRI, 4D-Flow MRI provides velocity data in all spatial directions, which allows for retrospective flow analysis of complex hemodynamic patterns at any plane of interest within the predefined anatomical region. In this study, we describe the use of 4D-Flow MRI for monitoring of comprehensive flow dynamics in a Potts shunt and the adjacent descending aorta and pulmonary arteries.