In this condition, increased resistance to the blood flow through the LUNGS occurs. This is usually the result of lung disease, and the consequence is an increase in pulmonary artery pressure, pressure in the right side of the heart and that in the veins bringing blood to the heart. Chronic BRONCHITIS or EMPHYSEMA commonly constricts the small arteries in the lungs, thus causing pulmonary HYPERTENSION. Other people at risk of the condition are those with SCLERODERMA, PORTAL HYPERTENSION, congenital heart disease and previous PULMONARY EMBOLISM. (See also EISENMENGER SYNDROME.)