title: Three-dimensional left atrial blood flow characteristics in patients with atrial fibrillation assessed by 4D flow CMR.
abstract: OBJECTIVE
  To apply 4D flow cardiac magnetic resonance (CMR) for the volumetric measurement of 3D left atrial (LA) blood flow to evaluate its potential to detect altered LA flow in patients with atrial fibrillation (AF) and to investigate associations of changes in systolic and diastolic LA flow with the current clinical risk score (CHA2DS2-VASc) used for the assessment of thromboembolic risk in AF.
  
  
  RESULTS
  4D flow CMR was performed in 40 patients with a history of AF (in sinus rhythm during CMR scan, age = 61 ± 11 years), 20 age-appropriate controls (59 ± 7 years), and 10 young healthy volunteers (24 ± 2 years) to measure in vivo time-resolved 3D LA blood flow. LA velocities were characterized with respect to atrial function and timing by calculating normalized LA flow velocity histograms during ventricular systole, early diastole, mid-late diastole, and the entire cardiac cycle. Mean, median, and peak LA velocity steadily decreased when comparing young volunteers, age-appropriate controls, and AF patients by 10-44% and 8-26% for early diastole and the entire cardiac cycle, respectively (P < 0.01 for all comparisons except median velocity for young vs. older volunteers and peak velocity for older volunteers and AF patients). There were moderate but significant inverse relationships between increased CHA2DS2-VASc score and reduced mean LA velocity (early diastole: r = -0.37, P < 0.001; entire RR-interval: r = -0.33, P = 0.005), median LA velocity (r = -0.33, P = 0.003; r = -0.25, P = 0.017), and peak velocity (r = -0.36, P = 0.001; r = -0.45, P < 0.001). LA flow indices also correlated significantly with age and LA volume (R2= 0.44-0.62, P < 0.001), but not with left ventricular ejection fraction.
  
  
  CONCLUSIONS
  Left atrial 4D flow CMR demonstrated significantly reduced LA blood flow velocities in patients with AF. Further study is needed to determine whether these measures can improve upon the CHA2DS2-VASc score for stroke risk prediction and enhance individual decisions on anticoagulation in patients with AF.
authors.affiliation: Feinberg Cardiovascular Research Institute, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.|Department of Radiology, Northwestern University Feinberg School of Medicine, 737 N. Michigan Avenue Suite 1600, Chicago, IL 60611, USA.|Division of Cardiology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Lee
authors.affiliation: Department of Radiology, Northwestern University Feinberg School of Medicine, 737 N. Michigan Avenue Suite 1600, Chicago, IL 60611, USA mmarkl@northwestern.edu.|Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, IL, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Markl
authors.affiliation: Feinberg Cardiovascular Research Institute, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.|Division of Cardiology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
authors.forename: Jason
authors.initials: J
authors.lastname: Ng
authors.affiliation: Department of Radiology, Northwestern University Feinberg School of Medicine, 737 N. Michigan Avenue Suite 1600, Chicago, IL 60611, USA.
authors.forename: Maria
authors.initials: M
authors.lastname: Carr
authors.affiliation: Feinberg Cardiovascular Research Institute, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
authors.forename: Brandon
authors.initials: B
authors.lastname: Benefield
authors.affiliation: Department of Radiology, Northwestern University Feinberg School of Medicine, 737 N. Michigan Avenue Suite 1600, Chicago, IL 60611, USA.
authors.forename: James C
authors.initials: JC
authors.lastname: Carr
authors.affiliation: Feinberg Cardiovascular Research Institute, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.|Division of Cardiology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.|Center for Cardiovascular Innovation, Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Goldberger
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D001281:Atrial Fibrillation / Q000000981:diagnostic imaging* / Q000503:physiopathology; D016279:Atrial Function, Left / Q000502:physiology; D001783:Blood Flow Velocity / Q000502:physiology; D016022:Case-Control Studies; D019561:Echocardiography, Four-Dimensional / Q000379:methods*; D019560:Echocardiography, Three-Dimensional / Q000379:methods*; D005260:Female; D006801:Humans; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D008875:Middle Aged; D016011:Normal Distribution; D011379:Prognosis; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D018709:Statistics, Nonparametric; D013318:Stroke Volume; D055815:Young Adult
keywords: 4D flow CMR; atrial fibrillation; cardiovascular MRI; flow; stroke