A patient with pulmonary embolism develops hemoptysis. What is the pathophysiologic cause?

In pulmonary embolism, an embolus occludes a pulmonary artery, blocking blood flow to a segment of lung tissue. When this ischemia is prolonged and severe enough, the affected lung tissue undergoes infarction — cell death due to oxygen deprivation. The infarcted tissue loses its structural integrity, and blood from damaged capillaries leaks into the airways and alveoli, producing hemoptysis. This explains why hemoptysis, while not present in all pulmonary embolism cases, occurs specifically when infarction has taken place. Pleural effusion involves fluid accumulation in the pleural space and can cause dyspnea and pleuritic chest pain but does not directly cause coughing up blood. Bronchospasm is a narrowing of the airways that causes wheezing and air trapping but does not produce blood in the sputum. Infection such as pneumonia can cause hemoptysis, but in the clinical context of a known pulmonary embolism, the pathophysiologic mechanism is tissue infarction, not an infectious process. Recognizing the direct link between vascular occlusion, downstream ischemia, and tissue necrosis leading to bleeding into the airways is essential for understanding why hemoptysis develops in pulmonary embolism.