Caval contribution to flow in the branch pulmonary arteries of Fontan patients with a novel application of magnetic resonance presaturation pulse

Background-A complete understanding of fluid mechanics in Fontan physiology includes knowledge of the caval contributions to right (RPA) and left (LPA ) pulmonary arterial blood flow, total systemic Venous return, and relative blood flow to each lung. Methods and Results-Ten Fontan patients underwent cine MRT. Three cine scan s of the pulmonary arteries were performed: (1) no presaturation pulse, (2) a presaturation pulse labeling inferior vena cava (IVC) blood (signal void ), and (3) a presaturation pulse labeling superior vena cava (SVC) blood. T he relative signal decrease is proportional to the amount of blood originat ing from the labeled vena cava. This method was validated in a phantom. Whe reas 60+/-6% of SVC blood flowed into the RPA, 67+/-12% of IVC blood flowed toward the LPA. Of the blood in the LPA and RPA, 48+/-14% and 31+/-17%, re spectively, came from the IVC. IVC blood contributed 40+/-16% to total syst emic venous return. The distributions of blood to each lung were nearly equ al (RPA/LPA blood=0.94+/-11). Conclusions-In Fontan patients with total cavopulmonary connection, SVC blo od is directed toward the RPA and IVC blood is directed toward the LPA. Alt hough the right lung volume is larger than the left, an equal amount of blo od flow went to both lungs. LPA blood is composed of equal amounts of IVC a nd SVC blood because IVC contribution to total systemic venous return is sm aller than that of the SVC, This technique and these findings can help to e valuate design changes of the systemic venous pathway to improve Fontan hem odynamics.