Poster Presentation & Flash Talk 46th Annual Meeting of the Fetal and Neonatal Physiological Society 2019

4D flow magnetic resonance imaging in neonatal piglets: A tool for visualizing and quantifying ductus arteriosus blood flow (#114)

Eric M. Schrauben 1 , Jack R.T. Darby 2 , Mary J. Berry 3 , Megan Quinn 2 , Stacey L. Holman 2 , Mitchell C. Lock 2 , Mike Seed 4 5 , Christopher K. Macgowan 1 6 , Janna L. Morrison 2
  1. Translational Medicine, Hospital for Sick Children, Toronto, Ontario, Canada
  2. Early Origins of Adult Health Research Group, School of Pharmacy & Medical Sciences, University of South Australia, Adelaide, SA, Australia
  3. Centre for Translational Physiology & Department of Pediatrics and Child Health, University of Otago, Wellington, New Zealand
  4. Division of Cardiology, Hospital for Sick Children, Toronto, Ontario, Canada
  5. Department of Paediatrics, University of Toronto, Toronto, Ontario, Canada
  6. Medical Biophysics, University of Toronto, Toronto, Ontario, Canada

Fetal and postnatal circulation differs due to the need to deliver oxygen- and nutrient-rich blood from the placenta to organs such as the fetal heart and brain. This is enabled through additional pathways including the ductus arteriosus (DA). Upon birth, lung aeration rapidly decreases pulmonary vascular resistance, increasing pulmonary blood flow while closing the DA. However, this often takes 2-3 days; in preterm neonates DA closure is even more delayed1. Abnormal persistent opening of the DA can induce left-to-right blood shunting, termed ‘ductal steal,' and may lead to pulmonary hypertension and compromised perfusion of vital organs.

Here we present an in vivo technique to comprehensively visualize and quantify DA blood flow. Twenty-one neonatal piglets were either delivered preterm (106 days; n=5) or at term (112 days; n=16). A carotid arterial catheter was placed for cardiac cycle-triggered MRI. Anaesthesia was maintained via continuous propofol infusion. MRI used a volumetric phase contrast technique, 4D flow MRI2, which enables whole volume blood flow visualization and measurement (Figure 1). At term, the DA was open in 10 piglets and closed in 6; open DA was observed in 4/5 preterm piglets. Blood flow was measured in 7 major vessels. Patterns of ductal steal were observed in n=7 of the term neonates.

The optimal clinical care for persistent DA flow in preterm infants remains uncertain. Defining vascular biomechanics in clinically relevant translational models of human preterm birth will provide novel insights and ultimately a platform for clinical innovation.

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Figure 1. a:  Ductus arteriosus (DA) flow visualization with steal of aortic flow (dotted black arrow). b-d: Blood flow waveforms (mean±SEM) over groups of neonatal piglets. Observed differences in term piglets with reversed DA flow include retrograde diastolic flow in the descending aorta (distal to the DA, c) and higher pulmonary blood flow (d).

  1. Benitz, W.E., Patent Ductus Arteriosus in Preterm Infants. Pediatrics, 2016. 137(1): p. e20153730.
  2. Markl, M., et al., 4D flow MRI. J Magn Reson Imaging, 2012. 36(5): p. 1015-36.