The heart and lungs work together. The heart pumps oxygen-rich blood from the lungs into the arteries and pumps deoxygenated blood from the veins into the lungs for reoxygenation. COPD decreases oxygen levels and causes the lung's blood vessels to narrow making it difficult for the heart to pump blood into the lungs. Over time, the heart muscle weakens and pumps less effectively. This is a type of heart failure.