Cor pulmonale, also known as pulmonary heart disease, is a type of heart disease where the right side of the heart enlarges and fails over time due to high blood pressure in the lungs or pulmonary hypertension. It develops in response to lung diseases like chronic obstructive pulmonary disease (COPD) that cause restricted breathing and low oxygen levels in the blood. Symptoms include leg swelling, fatigue, dizziness, and chest pain.