title: Effects of exercise and respiration on blood flow in total cavopulmonary connection: a real-time magnetic resonance flow study.
abstract: BACKGROUND
  Little is known about blood flow and its relationship to respiration during exercise in patients with total cavopulmonary connection (TCPC).
  
  
  RESULTS
  We studied 11 patients 12.4+/-4.6 years (mean+/-SD) of age 5.9+/-2.8 years (mean+/-SD) after TCPC operation. Real-time MRI was used to measure blood flow in the superior vena cava (SVC), inferior vena cava (IVC), and ascending aorta under inspiration and expiration during supine lower-limb exercise (rest, 0.5 and 1.0 W/kg) on an ergometer bicycle. IVC and aortic flow increased from 1.60+/-0.52 and 2.99+/-0.83 L/min per m2 at rest to 2.58+/-0.71 and 3.97+/-1.20 L/min per m2 at 0.5 W/kg and to 3.25+/-1.23 and 4.62+/-1.49 L/min per m2 at 1.0 W/kg (P< or =0.05). SVC flow remained unchanged. Resting flow in the IVC was greater during inspiration (2.99+/-1.25 L/min per m2) than during expiration (0.83+/-0.44 L/min per m2) (inspiratory/mean flow ratio, 1.9+/-0.5), and retrograde flow was present during expiration (11+/-12% of mean flow). The predominance of inspiratory flow in IVC diminished with exercise to an inspiratory/mean flow ratio of 1.5+/-0.2 (P< or =0.05) and 1.4+/-0.3 at 0.5 and 1.0 W/kg, respectively.
  
  
  CONCLUSIONS
  In the TCPC, circulation IVC and aortic but not SVC flows increase with supine leg exercise. Inspiration facilitates IVC flow at rest but less so during exercise, when the peripheral pump seems to be more important.
authors.affiliation: Department of Cardiothoracic and Vascular Surgery, Skejby Hospital, Aarhus University Hospital, DK-8200 Aarhus N, Denmark. vibeke.hjortdal@dadlnet.dk
authors.forename: V E
authors.initials: VE
authors.lastname: Hjortdal
authors.forename: K
authors.initials: K
authors.lastname: Emmertsen
authors.forename: E
authors.initials: E
authors.lastname: Stenbøg
authors.forename: T
authors.initials: T
authors.lastname: Fründ
authors.forename: M Rahbek
authors.initials: MR
authors.lastname: Schmidt
authors.forename: O
authors.initials: O
authors.lastname: Kromann
authors.forename: K
authors.initials: K
authors.lastname: Sørensen
authors.forename: E M
authors.initials: EM
authors.lastname: Pedersen
mesh_terms: D001011:Aorta / Q000502:physiology; D001783:Blood Flow Velocity; D002648:Child; D004452:Echocardiography; D004562:Electrocardiography; D015444:Exercise / Q000502:physiology; D005080:Exercise Test; D005260:Female; D018729:Fontan Procedure; D018610:Heart Bypass, Right; D006330:Heart Defects, Congenital / Q000503:physiopathology / Q000601:surgery; D006339:Heart Rate; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D012119:Respiration; D012146:Rest / Q000502:physiology; D013318:Stroke Volume; D014682:Vena Cava, Inferior / Q000502:physiology; D014683:Vena Cava, Superior / Q000502:physiology