title: Respiratory Effects on Fontan Circulation During Rest and Exercise Using Real-Time Cardiac Magnetic Resonance Imaging.
abstract: BACKGROUND
  It is known that respiration modulates cavopulmonary flows, but little data compare mean flows under breath-holding and free-breathing conditions to isolate the respiratory effects and effects of exercise on the respiratory modulation.
  
  
  METHODS
  Real-time phase-contrast magnetic resonance combined with a novel method to track respiration on the same image acquisition was used to investigate respiratory effects on Fontan caval and aortic flows under breath-holding, free-breathing, and exercise conditions. Respiratory phasicity indices that were based on beat-averaged flow were used to quantify the respiratory effect.
  
  
  RESULTS
  Flow during inspiration was substantially higher than expiration under the free-breathing and exercise conditions for both inferior vena cava (inspiration/expiration: 1.6 ± 0.5 and 1.8 ± 0.5, respectively) and superior vena cava (inspiration/expiration: 1.9 ± 0.6 and 2.6 ± 2.0, respectively). Changes from rest to exercise in the respiratory phasicity index for these vessels further showed the impact of respiration. Total systemic venous flow showed no significant statistical difference between the breath-holding and free-breathing conditions. In addition, no substantial difference was found between the descending aorta and inferior vena cava mean flows under either resting or exercise conditions.
  
  
  CONCLUSIONS
  This study demonstrated that inferior vena cava and superior vena cava flow time variance is dominated by respiratory effects, which can be detected by the respiratory phasicity index. However, the minimal respiration influence on net flow validates the routine use of breath-holding techniques to measure mean flows in Fontan patients. Moreover, the mean flows in the inferior vena cava and descending aorta are interchangeable.
authors.affiliation: Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia.
authors.forename: Zhenglun
authors.initials: Z
authors.lastname: Wei
authors.affiliation: Division of Cardiology and Department of Radiology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
authors.forename: Kevin K
authors.initials: KK
authors.lastname: Whitehead
authors.affiliation: Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia.
authors.forename: Reza H
authors.initials: RH
authors.lastname: Khiabani
authors.affiliation: Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia.
authors.forename: Michael
authors.initials: M
authors.lastname: Tree
authors.affiliation: Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia.
authors.forename: Elaine
authors.initials: E
authors.lastname: Tang
authors.affiliation: Division of Cardiology and Department of Radiology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Paridon
authors.affiliation: Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Fogel
authors.affiliation: Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia. Electronic address: ajit.yoganathan@bme.gatech.edu.
authors.forename: Ajit P
authors.initials: AP
authors.lastname: Yoganathan
mesh_terms: D000293:Adolescent; D001011:Aorta / Q000000981:diagnostic imaging / Q000503:physiopathology*; D001783:Blood Flow Velocity; D003199:Computer Systems; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D018729:Fontan Procedure; D018056:Hemorheology; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D011652:Pulmonary Circulation; D011673:Pulsatile Flow; D012119:Respiration; D015656:Respiratory Mechanics; D012146:Rest / Q000502:physiology*; D035441:Thoracic Wall / Q000000981:diagnostic imaging; D014684:Venae Cavae / Q000000981:diagnostic imaging / Q000503:physiopathology*; D055815:Young Adult