Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 59 5 2021 07 05 280 284 Ghazaleh Doostparast Torshizi Department of Pediatrics, Division of Environmental Pediatrics, NYU Langone Medical Center, New York, NY, USA. AND Department of Pediatrics, Hakim Hospital, Neyshabur University of Medical Sciences, Neyshabur, Iran Mahboobe Gholami Department of Midwifery, Hakim Hospital, Neyshabur University of Medical Sciences, Neyshabur, Iran Behzad Alizadeh Department of Pediatrics Cardiology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran 2020 06 24 2021 04 16 Down syndrome (DS) is a genetic impairment associated with comorbidities such as Congenital Heart Disease (CHD). Pulmonary Arterial Hypertension (PAH) is a complication of CHD in most patients. Due to insufficient documents about the prevalence of PAH in DS with CHDs compared to non-DS (NDS)+CHD patients, this study aimed to compare the prevalence of PAH between DS-CHD and NDS-CHD patients. This is a cross-sectional study conducted on DS-CHD patients referred to the Pediatric and Congenital Cardiology Division at Imam Reza training hospital in Mashhad, Iran, between April 2015 and February 2016. The comparison group included NDS-CHD children matched in terms of age and gender. A comprehensive Echocardiography was run for all patients to determine the types of CHD and pulmonary arterial pressure. Seventy-seven patients were enrolled in the study (47 in the DS-CHD group and 30 in the NDS-CHD group). 48.9% of the DS-CHD patients and 23.3% of the NDS-CHD group developed PAH, which revealed a significantly higher rate of PH among DS-CHD patients (P=0.025). Our findings denote a higher prevalence of PAH among DS-CHD patients compared to NDS-CHD patients. Such an observation is a meaningful warning for DS patients to take early necessary medical or corrective therapies for CHD in order to prevent complications and irreversible pulmonary vascular disease. https://acta.tums.ac.ir/index.php/acta/article/view/8575