The purpose of this study is to describe the evolution of pulmonary artery hypertension after repair of complete atrioventricular canal defect and to determine the time to normalisation of pulmonary artery pressure in both patients with and without Trisomy 21. This is a single centre, retrospective analysis of patients with complete atrioventricular canal defect admitted for surgical repair at the University of Maryland Medical Center from 2005 to 2015. T-test or Mann-Whitney test and Chi-Square or Fisher's exact tests were used to compare the two groups (patients with Trisomy 21 and those without). Repeated measures of analysis of variance and serial measurement analysis were performed. Twenty-nine patients meeting the inclusion criteria underwent repair of complete atrioventricular defects during the study period. The right ventricular pressure estimate remained elevated over time and did not show a significant difference between the two groups. Right ventricular to systolic blood pressure ratios for all patients remained > 0.5 over the time periods assessed. Our study suggests that in patients with complete atrioventricular canal defects, the right ventricular pressure remains elevated and does not normalise on echocardiograms performed up to one year after surgery, suggesting a sustained elevation in pulmonary vascular resistance.