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 whether 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 (r2 = 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.NEW & NOTEWORTHY This study shows that patients with single ventricles exhibit lower longitudinal systolic function than healthy subjects. The longitudinal contribution to stroke volume was about 40% compared with ∼80% in a normal right ventricle and 60% in a normal left ventricle. This difference is likely related to the passive blood flow through the lungs and did not change after Fontan completion. Furthermore, atrioventricular coupling seems to be preserved despite previous pericardiotomies.