Infants with single ventricle congenital heart disease demonstrate increasing head growth after bidirectional Glenn; however, the expected growth trajectory has not been well described.

1) We will describe the pattern of head circumference growth in the first year after bidirectional Glenn. 2) We will determine if head growth correlates with motor developmental outcomes approximately 12 months after bidirectional Glenn.

Sixty-nine single ventricle patients underwent bidirectional Glenn between 2010 and 2016. Patients with structural brain abnormalities, grade III–IV intra-ventricular haemorrhage, significant stroke, or obstructive hydrocephalus were excluded. Head circumference and body weight measurements from clinical encounters were evaluated. Motor development was measured with Psychomotor Developmental Index of the Bayley Scales of Infant Development, Third Edition. Generalised estimating equations assessed change in head circumference z-scores from baseline (time of bidirectional Glenn) to 12 months post-surgery.

Mean age at bidirectional Glenn was 4.7 (2.3) months and mean head circumference z-score based on population-normed data was −1.13 (95% CI −1.63, −0.63). Head circumference z-score increased to 0.35 (95% CI −0.20, 0.90) (p < 0.0001) 12 months post-surgery. Accelerated head growth, defined as an increase in z-score of >1 from baseline to 12 months post-surgery, was present in 46/69 (66.7%) patients. There was no difference in motor Psychomotor Developmental Index scores between patients with and without accelerated head growth.

Single ventricle patients demonstrated a significant increase in head circumference after bidirectional Glenn until 10–12 months post-surgery, at which time growth stabilised. Accelerated head growth did not predict sub-sequent motor developmental outcomes.