The heart and lung are intricately linked. When the heart is affected by disease, the lungs will often show some related pathological or clinical conditions and vice versa. Pulmonary heart disease is by definition a condition when the lungs cause the heart to fail. The left ventricle in combination with the other structures in the "left heart" pumps blood throughout the body. The right ventricle (and structures of the "right heart") pumps blood to the lungs where it is oxygenated and returned to the left heart for distribution. In normal circumstances, the right heart pumps blood into the lungs without any resistance. The lungs usually have minimal pressure and the right heart easily pumps blood through. However when there is lung disease present, like emphysema, chronic obstructive lung disease (COPD) or pulmonary hypertension- the small blood vessels become very stiff and rigid. The right ventricle is no longer able to push blood into the lungs and eventually fails. This is known as pulmonary heart disease. Pulmonary heart disease is also known as right heart failure or cor pulmonale. The chief cause of right heart failure is the increase in blood pressure in the lungs (pulmonary artery).