Normal and adverse pulmonary arterial flow patterns after the Fontan procedure and correlation with invasive CMR (iCMR) hemodynamics: A retrospective observational study.

Background: Branch pulmonary artery flow patterns in the Fontan circulation manifest oscillations reflecting venous pressure changes. The clinical importance of variation in branch pulmonary artery flow patterns and the relationship with the single ventricle performance is not understood. We describe insights gained from simultaneous hemodynamic and phase contrast magnetic resonance using interventional CMR (iCMR) in these patients.

Method: Twenty-seven patients with Fontan circulation referred for iCMR were studied using phase-contrast velocity mapping. The isovolumetric relaxation period (IVRT) was assessed using standard or velocity-encoded cine imaging of the atrioventricular valve (AVV) and aortic valve. We qualitatively assessed branch pulmonary artery flows considering four patterns: IVRT flow reversal, IVRT flow reaching baseline, and normal - phasic flow or continuous flow. We further collected comprehensive left and right heart iCMR hemodynamic and flow data, including pressures, aortopulmonary collateral (APC) burden, and degree of AVV regurgitation.

Results: Most patients underwent extracardiac Fontan palliation and did not have significant APC burden. Cardiac cycle analysis demonstrated that flow reversal and flow reaching baseline correlated with IVRT (v-wave timing on SVC pressure). Further analysis showed statistically significant difference in pulmonary capillary wedge pressure (PCWp) v-wave (P = .008) among the described groups. Notably, patients with IVRT flow reversal pattern had higher PCWp v-wave and most had severe AVV regurgitation.

Conclusion: Branch pulmonary artery IVRT flow reversal and IVRT baseline patterns in patients with Fontan circulation may represent indirect signs of single ventricle poor performance and severe AVV regurgitation.