Unilateral absence of the pulmonaryartery (UAPA) is a heart defect that is present from birth. The pulmonary arterytakes blood from the heart to the lungs. In the absence of a pulmonaryartery, other blood vessels compensate by supplying blood to thelungs. Pressure can build inside these vessels and lead to heart and lungcomplications. UAPA can be left sided orright sided. It most often occurs alone, but can occur with other heartanomalies and birth defects. Signs and symptoms include repeat lunginfections, lower exercise tolerance, shortness of breath, chest pain, andfluid in the lungs. Risk for these symptoms increase with age.Complications of UAPA include, hemoptysis (coughing up blood), respiratory hemorrhage,and high blood pressure in the arteries to the lung (pulmonaryhypertension). Serious complications may be triggered by stress onthe body, such as pregnancy and altitude sickness.