Regular physicals can help diagnose heart problems.
Normal asthma occurs when the bronchial openings narrow. These bronchial openings lead to the alveoli in the lungs, where gas exchange occurs. This narrowing occurs as a result of either swelling or muscular contraction. Cardiac asthma, however, occurs when fluid builds up in the lungs--a symptom known as pulmonary edema. This causes wheezing, coughing and shortness of breath (SOB), which can be life-threatening if untreated. Pulmonary edema is a symptom of several other diseases.
Pulmonary Venous Pressure
The immediate cause of pulmonary edema is simply an increase in pulmonary venous pressure, meaning that more blood than usual is in the veins that run between the lungs and the heart. This is known as backward failure. With the rise in pressure, there is little time to compensate for the increased vascular volume; the layer of cells that allows only gases to permeate begins allowing fluid to pass. This fluid builds up in the lungs' spaces, and breathing becomes restricted and difficult.
Cardiac Muscle Dysfunction
Pulmonary edema can occur as a result of several heart muscle problems. The most common cause is abnormal systolic function--problems with the heart during the contraction phase of a patient's heartbeat. Diseases that cause systolic dysfunction include coronary artery disease (CAD), a toxin present in the blood stream, and myocarditis, which is inflammation of the heart muscle. Systolic dysfunction causes increases in pulmonary venous pressure because the volume of blood being pushed from the heart is less than the amount being sent to the heart, causing a back-up in the pulmonary vessels. Diastolic dysfunction can also cause pulmonary edema. Causes of dysfunction during diastole, the relaxation and filling phase of hearbeat, include heart muscle diseases, lack of blood flow and high blood pressure.
Heart Valves
Pulmonary edema can result from problems with the valves in the heart. If the mitral opening narrows--a condition called mitral stenosis--the amount of blood reaching the left ventricle diminishes, resulting in a back-up in the pulmonary veins. The mitral opening separates the left atrium and ventricle. This occurs, most often, as a result of rheumatic heart disease, in which the mitral valves and chordae tendineae thicken and stiffen. Chordae tendineae keep the mitral valve from backing up into the atrium, a condition called mitral valve prolapse. After blood reaches the left ventricle, the aorta carries it on to the rest of the body. If the aortic valve narrows (aortic stenosis), a diminished amount of blood can leave the ventricle. Also, in a condition called aortic regurgitation, blood that reaches the aorta flows back into the ventricle due to dysfunction of the aortic valves. These aortic valve problems can cause the back-up that results in pulmonary edema.
Other Causes
The other causes of cardiac asthma are less common, but worth noting. Narrowing of the renal artery, or renal artery stenosis (RAS), can cause pulmonary edema. In some cases, edema has been the only symptom by which RAS was diagnosed. A benign tumor of the atrial wall, called atrial myxoma, and a blood clot inside the heart, known as an intracardiac thrombus, may also present pulmonary edema as a symptom.
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