Flow during exercise in the total cavopulmonary connection measured by magnetic resonance velocity mapping.
OBJECTIVE
To measure caval and pulmonary flows at rest and immediately after exercise in patients with total cavopulmonary connection (TCPC).


METHODS
An observational study using the patients as their own controls.


METHODS
Using a combination of magnetic resonance (MR) phase contrast techniques and an MR compatible bicycle ergometer, blood flow was measured in the superior vena cava, the tunnel from the inferior vena cava, and in the left and right pulmonary arteries during rest and on exercise (0.5 W/kg and 1.0 W/kg).


METHODS
Eleven patients aged 11.4 (4.6) years (mean (SD)) were studied 6.3 (3.8) years after TCPC operation.


METHODS
Volume flow measured in all four branches of the TCPC connection during rest and exercise.


RESULTS
Systemic venous return (inferior vena cava plus superior vena cava) increased from 2.5 (0.1) l/min/m2 (mean (SEM)) to 4.4 (0.4) l/min/m2 (p < 0.05) during exercise, with even distribution to the two pulmonary arteries. At rest, inferior vena caval flow was higher than superior vena caval flow, at 1.4 (0.1) v 1.1 (0.1) l/min/m2 (p < 0.05). During exercise, inferior vena caval flow doubled (to 3.0 (0.3) l/min/m2) while superior vena caval flow only increased slightly (to 1.4 (0.1) l/min/m2) (p < 0.05). The increased blood flow mainly reflected an increase in heart rate. The inferior vena caval to superior vena caval flow ratio was 1.4 (0.1) at rest and increased to 1.8 (0.1) (p < 0.05) at 0.5 W/kg, and to 2.2 (0.2) at 1.0 W/kg (p < 0.05).


CONCLUSIONS
Quantitative flow measurements can be performed immediately after exercise using MR techniques. Supine leg exercise resulted in a more than twofold increase in inferior vena caval flow. This was equally distributed to the two lungs, indicating that pulmonary resistance rather than geometry decides flow distribution in the TCPC circulation.
Pedersen
E M
EM
Department of Cardiology, Aarhus University Hospital, Aarhus, Denmark. erik.morre@iekf.au.dk
Stenbøg
E V
EV
Fründ
T
T
Houlind
K
K
Kromann
O
O
Sørensen
K E
KE
Emmertsen
K
K
Hjortdal
V E
VE
D001783:Blood Flow Velocity; D002648:Child; D015444:Exercise / Q000502:physiology*; D005260:Female; D018729:Fontan Procedure / Q000379:methods*; D006330:Heart Defects, Congenital / Q000503:physiopathology* / Q000601:surgery; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D018810:Magnetic Resonance Angiography / Q000379:methods; D008297:Male; D011182:Postoperative Care; D011651:Pulmonary Artery / Q000502:physiology*; D011652:Pulmonary Circulation / Q000502:physiology*; D013318:Stroke Volume / Q000502:physiology; D014682:Vena Cava, Inferior / Q000502:physiology; D014683:Vena Cava, Superior / Q000502:physiology*