Figure 2.

Pulmonary regurgitation measured by MRI through-plane velocity mapping in repaired tetralogy of Fallot. (a) Cine imaging aligned with the right ventricular outflow tract showed no effective pulmonary valve. Mapping of velocities through (b) a plane transecting the main pulmonary artery showed (c) systolic forward flow, diastolic reversed flow and late diastolic forward flow at the time of atrial systole. Absence of effective valve action typically results in a regurgitant fraction of ∼35–45%, only occasionally exceeding 50%, for example if exacerbated by branch pulmonary artory stenosis or otherwise increased resistance distal to compliant arterial segments. RV, right ventricle.