Some children are born with defects in their heart and its chambers (congenital heart disease). An untreated congenital heart disease can cause heart failure in children. Some children may have hypertension as a result of a congenital heart disease in which their main blood vessel that carries blood from their heart to all of the organs of their body is narrowed (coarctation of aorta). Pulmonary hypertension is also a relatively common complication of congenital heart diseases like ventricular septal defect (hole in the wall that separates the two lower chambers of your heart), atrial septal defect (hole in the wall that separates the two upper chambers of your heart), persistent ductus arteriosus (failure of closure of the opening between the two major blood vessels leading from the heart after birth), etc.