Effective Cardiac Index and Systemic-Pulmonary Collaterals Evaluated by Cardiac Magnetic Resonance Late After Fontan Palliation

The regulation of cardiac output in the Fontan circuit is not completely understood. Systemic-pulmonary collaterals (SPCs) are frequent in patients with univentricular heart, and their clinical significance and management remain controversial. The aims of our study were to identify factors associated with SPCs' flow at late follow-up after Fontan and evaluate the relation between SPCs flow (QSPCs) and the effective cardiac index (CI). From our cardiac magnetic resonance database, we identified all Fontan patients with a complete set of flow measurements allowing calculation of QSPCs and effective CI. QSPCs was calculated as (left pulmonary veins flow + right pulmonary veins flow) − (right pulmonary artery flow + left pulmonary artery flow). Effective CI was calculated as (Aortic flow (QAo) − QSPCs)/BSA. Medical, surgical history, and clinical status were recorded. Sixty-four post-Fontan patients (36 male; mean age 19 ± 10 years) were included in the study. Median QSPCs was 0.7 L/min/m2 (interquartile [IQ] range 0.386-0.983) accounting for a median of 21% (IQ range 13-28) of aortic flow. The effective CI in our population was 2.4 ± 0.6 L/min/m2. QSPCs inversely correlate with left pulmonary artery area (r = −0.37, p = 0.004) and total antegrade pulmonary flow (r = −0.32, p = 0.01). QSPCs correlate with indexed aortic flow (r = 0.6, p <0.001) and inversely correlate with effective CI (r = −0.39, p = 0.002). Effective CI inversely correlates with age at study and age at the Fontan palliation (r = −0.35, p = 0.005, and r = −0.29, p = 0.02, respectively) and positively with ventricular ejection fraction (r = 0.3, p = 0.01). In conclusion, SPCs are common in Fontan patients, correlate inversely with effective CI, and are associated with a reduced antegrade pulmonary flow. In cardiac magnetic resonance evaluation of post-Fontan patients, effective CI should be taken into account rather than the total CI.