Obstruction of systemic pulmonary arterial shunts by diagnostic cardiac catheters

Accurate assessment of pulmonary artery pressure and pulmonary vascular resistance are essential in children who may be candidates for Fontan's operation.^1,2 In many such children, pulmonary blood flow is supplied primarily or entirely by systemic pulmonary arterial shunts. Because such shunts are frequently <5 mm in diameter, we proposed that passage of diagnostic cardiac catheters across these structures could partially obstruct the shunts, resulting in artifactually low measured pulmonary artery pressure and calculated pulmonary vascular resistance. This hypothesis was tested in an artificial circulation model and confirmed by clinical observations.