PULMONARY REGURGITATION IN THE LATE POSTOPERATIVE FOLLOW-UP OF TETRALOGY OF FALLOT - VOLUMETRIC QUANTITATION BY NUCLEAR-MAGNETIC-RESONANCE VELOCITY MAPPING

Background. Pulmonary regurgitation frequently occurs after surgical c orrection of tetralogy of Fallot. To date, reliable quantitation of pu lmonary regurgitation has not been possible, and therefore the clinica l significance of pulmonary regurgitation is controversial. Nuclear ma gnetic resonance (NMR) velocity mapping allows accurate measurement of volumetric flow. The feasibility and accuracy of NMR velocity mapping to quantify pulmonary regurgitation volumes are studied in patients a fter Fallot repair. Methods and Results. In 18 patients (mean age, 16. 5+/-6.5 years), late (12.6+/-5.2 years) after Fallot surgery, forward and regurgitant volume flow was measured in the main pulmonary artery with NMR velocity mapping. To validate the measurements of pulmonary f orward flow, right ventricular stroke volume was used as an internal r eference standard. Pulmonary regurgitation volumes were compared with the differences between the corresponding right and left ventricular s troke volumes. Ventricular volumes were measured with a multisection g radient echo NMR method. In addition, the relation between pulmonary r egurgitation and right ventricular volumes was studied. Measurements o f pulmonary regurgitation volume with NMR velocity mapping closely cor responded with the tomographically determined volumes (r=.93). Forward pulmonary volume flow was nearly identical to right ventricular strok e volume (r=.98). Pulmonary regurgitation volume was significantly cor related with end-diastolic volume (r=.82, P<.0005), end-systolic volum e (r=.63, P<.01), and stroke volume (r=.89, P<.0005) of the right vent ricle but not with right ventricular ejection fraction (r=-.41, P=NS). Conclusions. NMR velocity mapping is an accurate method for the noninv asive, volumetric quantification of pulmonary regurgitation after surg ical correction of tetralogy of Fallot.