Shunt Fraction (Echo)
The magnitude of an inra- or extracardiac shunt can be estimated by flow ratio between the pulmonary and systemic circulation (Qp/Qs) using echocardiography. It is important to remember that the systemic flow cannot be estimated using the LVOT if there is moderate to severe aortic insufficiency.
Consideration should be made to close shunts with flow rates > 1.5 if no contraindications exist.
Sanders SP et al.
Oh J, Seward JB, Tajik AJ.