Cor Pulmonale (Right Heart Enlargement and Failure): Due to pulmonary hypertension, the right ventricle of the heart must work excessively to pump blood through narrowed or obstructed pulmonary arteries. Over time, this leads to a thickening of the right ventricular walls (hypertrophy) and, initially, an enlargement to hold more blood. However, these compensatory mechanisms create a continuous extra load and stress on the right heart, ultimately causing the right ventricle to become insufficient and leading to heart failure.