Systemic-to-pulmonary collateral flow is a well-recognised phenomenon in patients with single ventricle physiology, but remains difficult to quantify. The aim was to compare the reported formula’s that have been used for calculation of systemic-to-pulmonary-collateral flow to assess their consistency and to quantify systemic-to-pulmonary collateral flow in patients with a Glenn and/or Fontan circulation using four-dimensional flow MRI (4D flow MR).

Retrospective case–control study of Glenn and Fontan patients who had a 4D flow MR study. Flows were measured at the ascending aorta, left and right pulmonary arteries, left and right pulmonary veins, and both caval veins. Systemic-to-pulmonary collateral flow was calculated using two formulas: 1) pulmonary veins – pulmonary arteries and 2) ascending aorta – caval veins. Anatomical identification of collaterals was performed using the 4D MR image set.

Fourteen patients (n = 11 Fontan, n = 3 Glenn) were included (age 26 [22–30] years). Systemic-to-pulmonary collateral flow was significantly higher in the patients than the controls (n = 10, age 31.2 [15.1–38.4] years) with both formulas: 0.28 [0.09–0.5] versus 0.04 [−0.66–0.21] l/min/m2 (p = 0.036, formula 1) and 0.67 [0.24–0.88] versus -0.07 [−0.16–0.08] l/min/m2 (p < 0.001, formula 2). In patients, systemic-to-pulmonary collateral flow differed significantly between formulas 1 and 2 (13% versus 26% of aortic flow, p = 0.038). In seven patients, veno-venous collaterals were detected and no aortopulmonary collaterals were visualised.

4D flow MR is able to detect increased systemic-to-pulmonary collateral flow and visualise collaterals vessels in Glenn and Fontan patients. However, the amount of systemic-to-pulmonary collateral flow varies with the formula employed. Therefore, further research is necessary before it could be applied in clinical care.

We aim to assess the safety and efficacy of the transcatheter balloon dilation of superior cavopulmonary anastomosis (SCPA).

SCPA stenosis can lead to impaired pulmonary blood flow, hypoxemia and development of veno-venous collaterals with right-to-left shunt. Balloon dilation of SCPA has been rarely reported and follow-up information is lacking.

We performed a retrospective review of patients who underwent cardiac catheterisation and angioplasty of SCPA and reviewed patient’s demographics, diagnosis, SCPA surgery and post-operative course, catheterisation haemodynamics, procedural technique, angiography, and the findings of follow-up catheterisation.

Between 2008 and 2017, seven patients showed significant narrowing of SCPA and underwent balloon angioplasty, all of whom had undergone bidirectional Glenn (BDG). Indications for cardiac catheterisation included persistent pleural effusion, hypoxemia, and echocardiographic evidence of BDG stenosis or routine pre-Fontan assessment. Five patients had bilateral SCPA. The procedure was successful in all cases with increase in the stenosis diameter from a median of 3.3 mm (range 1.2–4.7 mm) to a median of 4.7 mm (range 2.6–7.8 mm). All patients had at least one follow-up cardiac catheterisation. Only one patient required repeat angioplasty at the 2.3-month follow-up with no further recurrence. Sustained results and interval growth were noted in all other cases during up to 29 months of follow-up. No adverse events were encountered.

Based on our small series, balloon angioplasty of BDG stenosis is feasible and safe and appears to provide sustained improvement with interval growth and only the rare recurrence of stenosis.