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Published on: January 7, 2021
MRI Phase-Contrast Blood Flow in Fasting Pediatric Patients with Fontan Circulation Correlates with Exercise Capacity
Christopher Z Lam1, Dawn David1, Laura Acosta Izquierdo1
1Department of Diagnostic Imaging (C.Z.L., D.D., L.A.I., P.P., G.B.C., M.S., S.J.Y.), Division of Cardiology, Department of Paediatrics (A.I.D., E.J.S.M., R.R.C., R.M.W., M.S., S.J.Y.), and Division of Gastroenterology, Department of Paediatrics (S.C.L.), Hospital for Sick Children, University of Toronto, 555 University Ave, Toronto, ON, Canada M5G 1X8; Department of Medical Imaging, University of Toronto, Toronto, Canada (C.Z.L., L.A.I., G.B.C., S.J.Y.); Joint Department of Medical Imaging, University Health Network, Toronto, Canada (R.M.W.); and Peter Munk Cardiac Centre, University Health Network, Toronto General Hospital, Toronto, Canada (R.M.W.).
Insights
Pediatric patients with Fontan circulation show lower systemic blood flow on MRI compared to healthy children. This reduced blood flow is linked to decreased exercise capacity in these patients.
Area of Science:
- Cardiovascular Imaging
- Pediatric Cardiology
- Medical Physics
Background:
- The Fontan procedure is a palliative surgery for single-ventricle congenital heart defects.
- Assessing regional blood flow in pediatric patients post-Fontan circulation is crucial for understanding hemodynamics.
- Fasting conditions may influence blood flow measurements in cardiac MRI studies.
Purpose of the Study:
- To evaluate regional blood flow in pediatric patients with Fontan circulation using MRI.
- To establish reference ranges for systemic blood flow in fasting pediatric Fontan patients.
- To explore correlations between blood flow parameters and clinical status.
Main Methods:
- Retrospective analysis of clinical cardiac MRI data from pediatric patients (<18 years) who underwent the Fontan procedure.
- MRI scans were performed after at least 4 hours of fasting.
- Regional blood flow was quantified and compared to healthy volunteers, with statistical analysis including Mann-Whitney U, Kruskal-Wallis, chi-squared, and Spearman rank correlation tests.
Main Results:
- Fifty-five pediatric patients were included, with a median age of 14 years.
- Patients with Fontan circulation exhibited significantly lower ascending aortic, inferior vena cava, and total systemic blood flow compared to healthy controls (P < .001).
- Lower Fontan blood flow correlated inversely with pre-Fontan pulmonary artery pressure and ventricular end-diastolic pressure, and positively with post-Fontan oxygen consumption.
Conclusions:
- MRI provides reference ranges for regional systemic blood flow in fasting pediatric Fontan patients.
- Pediatric patients with Fontan circulation have reduced systemic blood flow compared to healthy individuals.
- Lower fasting blood flow in Fontan circulation is associated with diminished exercise capacity.
Purpose:
To assess regional blood flow in fasting pediatric patients with Fontan circulation by using MRI and to explore associations with clinical parameters.
Materials And Methods:
In this retrospective study, pediatric patients who had undergone the Fontan procedure (<18 years of age) and had undergone clinical cardiac MRI, performed after at least 4 hours of fasting, between 2018 and 2021 were included. Regional blood flow was compared with published healthy volunteer data (n = 19) and assessed in relation to hemodynamic parameters and clinical status. Data are presented as medians, with first to third quartiles in parentheses. Mann-Whitney U, Kruskal-Wallis, χ2, and Spearman rank correlation tests were used.
Results:
Fifty-five patients (38 boys) with median age at MRI of 14 years (IQR, 11-16 years) and median time from Fontan procedure to MRI of 10 years (IQR, 8-12 years) were included. Patients after Fontan procedure had lower ascending aortic, inferior vena cava, and total systemic blood flow compared with healthy volunteers (3.00 L/min/m2 [IQR, 2.75-3.30 L/min/m2] vs 3.61 L/min/m2 [IQR, 3.29-4.07 L/min/m2]; 1.73 L/min/m2 [IQR, 1.40-1.94 L/min/m2] vs 2.24 L/min/m2 [IQR, 2.06-2.75 L/min/m2]; 2.78 L/min/m2 [IQR, 2.45-3.10 L/min/m2] vs 3.95 L/min/m2 [IQR, 3.20-4.30 L/min/m2], respectively; P < .001). Portal vein flow was greater than hepatic vein flow in 25% of patients. Fontan blood flow was inversely correlated with pre-Fontan mean pulmonary artery pressure (Spearman rank correlation coefficient [r ]= -0.42, P = .005) and ventricular end diastolic pressure (r = -0.33, P = .04) and positively correlated with post-Fontan percent predicted oxygen consumption at peak workload (r = 0.34, P = .02).
Conclusion:
Reference ranges are provided for regional systemic blood flow derived by using MRI in fasting pediatric patients with Fontan circulation, who had lower systemic blood flow compared with healthy volunteers. Lower fasting Fontan blood flow correlated with lower exercise capacity.Keywords: Pediatrics, Heart, Congenital, MR Imaging, Hemodynamics/Flow Dynamics, Cardiac Supplemental material is available for this article. © RSNA, 2022.
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