Introduction: The hybrid procedure (HP) - bilateral pulmonary artery bands+ductal stent - is an alternative palliation for high-risk hypoplastic left heart syndrome (HLHS) patients. Assessment and management of atrial restriction here is debated and we sought to identify useful echocardiographic parameters. Methods: Patients undergoing HP for HLHS were identified. Echocardiograms at birth, immediately after HP and pre-and post-atrial intervention were reviewed as well as time-matched echocardiograms in HP patients not requiring atrial intervention. Atrial septal parameters and systolic (Svel), diastolic (Dvel) and mean velocities were recorded on both bands and systolic to diastolic velocity ratio (Svel:Dvel), pulsatility index (PI) and velocity time integral (VTI) calculated. Results: Fifteen HP were compared to 5 controls. Age effect was not significant. There was a significant rise in peak Svel and changes in Dvel, Svel:Dvel and PI over time (<0.05). Although the pattern of change similar, the fall in Dvel and rise in Svel:Dvel and PI was more significant on the left. Compared to controls, transatrial gradient and VTI were significantly increased initially post-hybrid (median 0.4m/s vs 0.7m/s p=0.04; 29.1cm vs 64.6cm p=0.018) but not significantly different prior to septostomy when the only significant differences were seen with all left band parameters. Conclusions: After HP the transatrial gradient alone cannot be used. Significant changes in band Doppler parameters were not apparent in the control group but were principally seen in the left band with reduction in Dvel and increase in Svel:Dvel and PI in those undergoing an atrial intervention.