Objective To assess flow dynamics after total cavopulmonary connection (TCPC).

Design Cross-sectional study.

Setting Aarhus University Hospital.

Patients Seven patients (mean age 9 (4–18) years) who had previously undergone a lateral tunnel TCPC mean 2 (0.3–5) years earlier.

Interventions Pressure recordings (cardiac catheterisation), flow volume, and temporal changes of flow in the lateral tunnel, superior vena cava, and right and left pulmonary arteries (magnetic resonance velocity mapping).

Results Superior vena cava flow was similar to lateral tunnel flow (1.7 (0.6–1.9)v 1.3 (0.9–2.4) l/min*m²) (NS), and right pulmonary artery flow was higher than left pulmonary artery flow (1.7 (0.6–4.3) v 1.1 (0.8–2.5) l/min*m², p < 0.05). The flow pulsatility index was highest in the lateral tunnel (2.0 (1.1–8.5)), lowest in the superior vena cava (0.8 (0.5–2.4)), and intermediate in the left and right pulmonary arteries (1.6 (0.9–2.0) and 1.2 (0.4–1.9), respectively). Flow and pressure waveforms were biphasic with maxima in atrial systole and late ventricular systole.

Conclusions Following a standard lateral tunnel TCPC, flow returning via the superior vena cava is not lower than flow returning via the inferior vena cava as otherwise seen in healthy subjects; flow distribution to the pulmonary arteries is optimal; and some pulsatility is preserved primarily in the lateral tunnel and the corresponding pulmonary artery. This study provides in vivo data for future in vitro and computer model studies.