Feasibility of quantification of the distribution of blood flow in the normal human fetal circulation using CMR: a cross
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RESEARCH
Open Access
Feasibility of quantification of the distribution of blood flow in the normal human fetal circulation using CMR: a cross-sectional study Mike Seed1,3*, Joshua F P van Amerom2, Shi-Joon Yoo3, Bahiyah Al Nafisi3, Lars Grosse-Wortmann1, Edgar Jaeggi1, Michael S Jansz2 and Christopher K Macgowan2
Abstract Background: We present the first phase contrast (PC) cardiovascular magnetic resonance (CMR) measurements of the distribution of blood flow in twelve late gestation human fetuses. These were obtained using a retrospective gating technique known as metric optimised gating (MOG). Methods: A validation experiment was performed in five adult volunteers where conventional cardiac gating was compared with MOG. Linear regression and Bland Altman plots were used to compare MOG with the gold standard of conventional gating. Measurements using MOG were then made in twelve normal fetuses at a median gestational age of 37 weeks (range 30–39 weeks). Flow was measured in the major fetal vessels and indexed to the fetal weight. Results: There was good correlation between the conventional gated and MOG measurements in the adult validation experiment (R=0.96). Mean flows in ml/min/kg with standard deviations in the major fetal vessels were as follows: combined ventricular output (CVO) 540±101, main pulmonary artery (MPA) 327±68, ascending aorta (AAo) 198±38, superior vena cava (SVC) 147±46, ductus arteriosus (DA) 220±39,pulmonary blood flow (PBF) 106±59, descending aorta (DAo) 273±85, umbilical vein (UV) 160±62, foramen ovale (FO)107±54. Results expressed as mean percentages of the CVO with standard deviations were as follows: MPA 60±4, AAo37±4, SVC 28±7, DA 41±8, PBF 19±10, DAo50±12, UV 30±9, FO 21±12. Conclusion: This study demonstrates how PC CMR with MOG is a feasible technique for measuring the distribution of the normal human fetal circulation in late pregnancy. Our preliminary results are in keeping with findings from previous experimental work in fetal lambs. Keywords: Regional blood flow, Magnetic resonance imaging, Circulation
Background Galen (AD 129–200) first described the presence of the ductus arteriosus, foramen ovale and placenta in the human fetus. However, it was not until 1628 that William Harvey introduced the concept of a fetal circulation with the right and left heart ejecting in parallel and shunting at the foramen ovale and arterial duct * Correspondence: [email protected] 1 Department of Paediatrics, Division of Paediatric Cardiology, University of Toronto, Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada 3 Department of Diagnostic Imaging, University of Toronto, Hospital for Sick Children, Toronto, Canada Full list of author information is available at the end of the article
bypassing the lungs [1]. In the second half of the twentieth century the distribution of the fetal circulation was studied in detail, initially by Dawes who made blood gas and flow measurements using plethysmography and intravascular flow probes in fetal lambs [2]. Rudolph and H
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