Completion of Fontan circulation does not affect the low longitudinal contribution to stroke volume in patients with single ventricles

Ventricular function is vital in patients with single ventricles but repeated surgeries and changes in ventricular volume load may change the relation between longitudinal and radial function. To expand the knowledge of cardiac mechanics in this population, the aim of this study was to assess longitudinal and radial contribution to stroke volume using cardiac magnetic resonance (CMR) imaging in patients before and after Fontan operation. We also aimed to assess if the atrioventricular coupling was intact in these patients despite multiple pericardiotomies. Twelve children underwent CMR before and after completion of Fontan circulation. Endocardial borders of the atria and the ventricle as well as the epicardial border of the heart were delineated. The percentage of the stroke volume attributed to longitudinal and radial function was calculated and pulmonary venous blood flow during the cardiac cycle was assessed. Longitudinal function correlated strongly with atrial filling (r 2 =0.90, ICC=0.92) and its contribution to stroke volume was 40 38-49 % before and 39 33-45 % after completion of Fontan circulation (p=0.092). All patients lacked the late systolic flow peak in the pulmonary veins corresponding to the lack of a normal right ventricle. In conclusion, patients with single ventricles exhibit preserved atrioventricular coupling but the ventricle has lower longitudinal and higher radial contribution to stroke volume as a consequence of the passive pulmonary blood flow relative to healthy hearts. Completion of Fontan circulation does not change this relationship.