Trouble with the human body may be approached from the point of view of its structure or its function. The heart may be enlarged, or its valves may leak or be narrowed, or its blood supply may be inadequate because of blocking. The changes in structure produce changes in function which are reflected in symptoms. From the functional point of view the heart may beat too fast or too slowly, or irregularly. Its beat may be weak or strong. The heart may be overactive or underactive.
When the heart is overactive people complain of palpitation. The heart sounds are loud and the pulse is full and bounding. Signs of an overactive heart may be seen when one has had severe exercise or emotional stress. With excessive action of the thyroid gland the heart beats more rapidly, as it does also with severe anemia. Whenever there is fever or lack of oxygen the heart becomes overly active.
When the circulation of blood through the blood vessels is insufficient because of failure of the heart, which means underactivity, the symptoms include apathy and lassitude, sometimes faintness, and collapse. If a sudden hemorrhage occurs the circulation fails. With failure of the heart the blood pressure falls and the skin becomes cold, clammy, dry, and inelastic.
In heart failure congestion of the lungs follows, with shortness of breath and the difficulty with breathing that occurs because of fluid. The doctor can hear with his stethoscope sounds in the lung that show the congestion. The patient coughs to get rid of the congestion.