Pulmonary edema, which is abnormal accumulation of fluid in the lungs, often occurs as a result of heart failure. Pulmonary edema occurs when the left ventricle of the heart, which receives oxygenated blood from the lungs, weakens and pumps less efficiently than normal. Because less blood leaves the heart with each contraction, fluid backs up into the top chamber of the heart, the left atrium and then into the lungs, because it has nowhere else to go. Damage to the left ventricle causes cardiac-related pulmonary edema, also called congestive heart failure.
Cardiomyopathy
Cardiomyopathy means damage to the heart muscle. Cardiomyopathy can have primary, meaning directly related to heart damage, or secondary causes. Cardiomyopathy may fall into one of three classifications: dilated, hypertrophic or restrictive. In dilated or congestive cardiomyopathy, the most common form, the heart muscle in the left ventricle stretches and pumps more weakly than normal, allowing blood to back up into the lungs. Hypertrophic cardiomyopathy occurs when the left ventricle thickens and enlarges. Around one in 500 people inherit hypertrophic cardiomyopathy, making it the most common inherited heart disease, the American Heart Association explains. In restrictive cardiomyopathy, the ventricle become stiff and less elastic, allowing less blood flow into the ventricle with each heartbeat.
Coronary Artery Disease
Coronary artery disease causes about half of all cases of pulmonary edema related to congestive heart failure, The Merck Manuals Online Medical Library reports. Plaque buildup in the arteries that supply blood to the heart decreases oxygen flow to the heart, which results in damage to the oxygen-starved muscle. The left ventricle pumps less efficiently and blood backs up into the lung. A previous heart attack can also leave the heart muscle permanently damaged.
Heart Valve Disorders
Problems with the valves that control blood flow through the heart can also cause pulmonary edema. Problems with the aortic valve and mitral valve most often lead to congestive heart failure. Blood flow through the left side of the heart is controlled by the mitral valve, which is found between the left atrium and left ventricle, while the aorta directs blood flow to the aorta from the left ventricle.
The mitral valve most commonly prolapses, or becomes floppy, and falls back into the atria during a heartbeat, the National Heart, Lung and Blood Institute explains. This allows blood to backflow into the atria rather than staying in the ventricle. The aortic valve can prolapse or become stenotic, which allows less blood to pass from the left ventricle through the aorta during each heartbeat. Fluid backs up in the ventricle, then into the atria and, eventually, into the lungs.
