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Published on: March 11, 2021
Completion of Fontan circulation does not affect the low longitudinal contribution to stroke volume in patients with
Pia Sjöberg1,2, Petter Frieberg1,2, Zahraa Alsafi3,4
1Clinical Physiology, Department of Clinical Sciences, Lund, Lund University, Lund, Sweden.
Insights
Single ventricle patients maintain atrioventricular coupling after Fontan operation. However, their ventricular function shows a lower longitudinal and higher radial contribution to stroke volume, a change not altered by the Fontan circulation.
Area of Science:
- Cardiovascular Physiology
- Pediatric Cardiology
- Medical Imaging
Background:
- Ventricular function is critical in single-ventricle patients, but surgical interventions and volume load shifts can alter the interplay between longitudinal and radial function.
- Understanding cardiac mechanics in these complex patients is essential for optimizing care.
Purpose of the Study:
- To quantify the longitudinal and radial contributions to stroke volume in single-ventricle patients before and after the Fontan operation.
- To evaluate the integrity of atrioventricular coupling in these patients, considering their history of multiple pericardiotomies.
Main Methods:
- Cardiac magnetic resonance (CMR) imaging was performed on twelve children before and after Fontan circulation.
- Endocardial and epicardial borders were delineated to calculate the percentage of stroke volume from longitudinal and radial function.
- Pulmonary venous blood flow was assessed throughout the cardiac cycle.
Main Results:
- Longitudinal function showed a strong correlation with atrial filling (r²=0.90, ICC=0.92).
- The contribution of longitudinal function to stroke volume was approximately 40% before and 39% after the Fontan operation, with no significant change (p=0.092).
- All patients lacked the typical late systolic pulmonary venous flow peak, indicative of altered ventricular dynamics.
Conclusions:
- Single-ventricle patients demonstrate preserved atrioventricular coupling despite multiple surgeries.
- The ventricle exhibits a reduced longitudinal and increased radial contribution to stroke volume due to passive pulmonary blood flow, a pattern unchanged by the Fontan procedure.
Abstract:
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.
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