title: 4D flow MRI assessment of right atrial flow patterns in the normal heart - influence of caval vein arrangement and implications for the patent foramen ovale.
abstract: OBJECTIVE
  To investigate atrial flow patterns in the normal adult heart, to explore whether caval vein arrangement and patency of the foramen ovale (PFO) may be associated with flow pattern.
  
  
  METHODS
  Time-resolved, three-dimensional velocity encoded magnetic resonance imaging (4D flow) was employed to assess atrial flow patterns in thirteen healthy subjects (6 male, 40 years, range 25-50) and thirteen subjects (6 male, 40 years, range 21-50) with cryptogenic stroke and patent foramen ovale (CS-PFO). Right atrial flow was defined as vortical, helico-vortical, helical and multiple vortices. Time-averaged and peak systolic and diastolic flows in the caval and pulmonary veins and their anatomical arrangement were compared.
  
  
  RESULTS
  A spectrum of right atrial flow was observed across the four defined categories. The right atrial flow patterns were strongly associated with the relative position of the caval veins. Right atrial flow patterns other than vortical were more common (p = 0.015) and the separation between the superior and inferior vena cava greater (10±5mm versus 3±3mm, p = 0.002) in the CS-PFO group. In the left atrium all subjects except one had counter-clockwise vortical flow. Vortex size varied and was associated with left lower pulmonary vein flow (systolic r = 0.61, p = 0.001, diastolic r = 0.63 p = 0.002). A diastolic vortex was less common and time-averaged left atrial velocity was greater in the CS-PFO group (17±2cm/sec versus 15±1, p = 0.048). One CS-PFO subject demonstrated vortical retrograde flow in the descending aortic arch; all other subjects had laminar descending aortic flow.
  
  
  CONCLUSIONS
  Right atrial flow patterns in the normal heart are heterogeneous and are associated with the relative position of the caval veins. Patterns, other than 'typical' vortical flow, are more prevalent in the right atrium of those with cryptogenic stroke in the context of PFO. Left atrial flow patterns are more homogenous in normal hearts and show a relationship with flow arising from the left pulmonary veins.
authors.affiliation: Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: Jehill D
authors.initials: JD
authors.lastname: Parikh
authors.affiliation: Department of Congenital Cardiology, Freeman Hospital, Newcastle upon Tyne, United Kingdom.
authors.forename: Jayant
authors.initials: J
authors.lastname: Kakarla
authors.affiliation: Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom.
authors.forename: Bernard
authors.initials: B
authors.lastname: Keavney
authors.affiliation: Department of Congenital Cardiology, Freeman Hospital, Newcastle upon Tyne, United Kingdom.|Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: John J
authors.initials: JJ
authors.lastname: O'Sullivan
authors.affiliation: Medical Sciences Division, University of Oxford, Oxford, United Kingdom.
authors.forename: Gary A
authors.initials: GA
authors.lastname: Ford
authors.affiliation: Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Blamire
authors.affiliation: Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: Kieren G
authors.initials: KG
authors.lastname: Hollingsworth
authors.affiliation: Department of Congenital Cardiology, Freeman Hospital, Newcastle upon Tyne, United Kingdom.|Medical Sciences Division, University of Oxford, Oxford, United Kingdom.
authors.forename: Louise
authors.identifier: http://orcid.org/0000-0003-3422-5497
authors.initials: L
authors.lastname: Coats
mesh_terms: D000328:Adult; D001013:Aorta, Thoracic / Q000033:anatomy & histology / Q000502:physiology; D004452:Echocardiography; D005260:Female; D054092:Foramen Ovale, Patent / Q000503:physiopathology*; D064368:Healthy Volunteers; D006325:Heart Atria / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006339:Heart Rate; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D055815:Young Adult