In pulmonary hypertension , failure of the left ventricle of the heart causes the lungs to be overloaded with fluid .
Because PDE5 is also present in the arterial wall smooth muscle within the lungs , PDE5 inhibitors have also been explored for the treatment of pulmonary hypertension , a disease in which blood vessels in the lungs become overloaded with fluid , usually as a result of failure of the right ventricle of the heart.