Diffuse Alveolar Hemorrhage in Cardiac Diseases.

Diffuse alveolar hemorrhage (DAH) is a rare condition with reported mortality ranging between 20 and 100%. There are many etiologies of DAH. Cardiac diseases are likely underreported causes of DAH. Heart failure and mitral valve diseases are the most common cardiac causes of DAH. The DAH results from pulmonary venous hypertension leading to stress failure of the pulmonary capillaries. There is also a contribution of the bronchial circulation. The Alveolar-capillary membrane or blood-gas barrier is an extremely thin structure that allows rapid and passive diffusion of oxygen from the inhaled air to the pulmonary capillaries while preventing pulmonary edema and DAH with chronic elevation of the transmural hydrostatic pressure. The purpose of this manuscript is to inform the clinician about this rare cause of DAH, which may be overlooked unless specifically sought after. We also discuss the pathophysiologic aspects of DAH and the safety mechanisms in place to prevent such occurrences.