To take the simplest example, what if something weakens the left ventricle so that it pumps a little less blood out of the lungs with each beat than the right ventricle pumps in [see figure]
This could happen for many reasons.
weakening of the heart muscle, a leaky valve, excessively high blood pressure. Imagine that the difference is as little as a drop and try some simple arithmetic to see what happens.
This could happen for many reasons.
weakening of the heart muscle, a leaky valve, excessively high blood pressure. Imagine that the difference is as little as a drop and try some simple arithmetic to see what happens.
A drop of blood equals about 0.1 cubic centimeter (cc). If the heart is beating 80 times a minute, there will be 8 cc of extra blood trapped in the lungs in 1 minute. In 1 hour there will be almost a pint of extra blood trapped in the lungs. This extra volume of blood will compress the small air passages. In addition, watery fluid will leak out of the overloaded capillaries into the tissue spaces between the air passages, with further compression.
There won't be room for a normal exchange of air, and the patient will become short of breath. (The medical term for shortness of breath - ”dyspnea”comes from the Greek stem dys, implying "abnormal" or "difficult", and pneumon, meaning "air".) Thus there is only one symptom of failure of the left ventricle: shortness of breath, or dyspnea.
This dyspnea can take several forms. It may appear very gradually, so that a golfer notes that he has to stop more often to get his breath, until one day he can hardly walk to the first tee. The patient, in effect, has become seriously disabled. This process can take weeks or it may progress very rapidly, in a matter of days, to the point at which the patient is confined to a chair or to a bed.
The dyspnea of left heart failure can take a terrifying, life-threatening form. The process of engorgement of the lungs can progress so rapidly that the air cells or alveoli actually fill with fluid. This condition is called acute pulmonary edema and it is a genuine medical emergency. The victim often wakens at night gasping, blue, and near death: the fluid has been quietly accumulating during sleep, and by the time the patient wakens there is barely enough oxygen exchange to sustain life. Without medical treatment, acute pulmonary edema is always fatal; with adequate medical measures, the patient can be out of danger in 10 or 15 minutes.
The dyspnea of left heart failure can take a terrifying, life-threatening form. The process of engorgement of the lungs can progress so rapidly that the air cells or alveoli actually fill with fluid. This condition is called acute pulmonary edema and it is a genuine medical emergency. The victim often wakens at night gasping, blue, and near death: the fluid has been quietly accumulating during sleep, and by the time the patient wakens there is barely enough oxygen exchange to sustain life. Without medical treatment, acute pulmonary edema is always fatal; with adequate medical measures, the patient can be out of danger in 10 or 15 minutes.
