Abstract: A system and accompanying method is provided for assessing a ratio of pulmonary to systemic blood flow in patients with a single-ventricle physiology (SVP). A compound dilution curve is recorded in an arterial vessel downstream of the pulmonary artery. A first component of the compound dilution curve is identified, wherein the first component is attributable to the indicator after passing through the single ventricle heart and directly into the arterial vessel A second component of the compound dilution curve is identified, wherein the second component is attributable to the indicator after passing from the single ventricle heart to the lungs, through the single ventricle heart and then to the arterial vessel downstream of the pulmonary artery. Based on the identified components, the pulmonary flow and systemic flow are assessed as corresponding to the identified first component and second component of the compound dilution curve.