Role of arterial pressure in the oedema of heart disease.

The primary function of the heart is maintenance of the arterial pressure that is essential for perfusion of the tissues. Cardiac output is mainly regulated by control systems acting through the arterial pressure, whereby the heart matches its output to the perfusion of the tissues, in which blood is distributed according to local vascular resistances. When the heart is disabled, the body intensifies to an abnormal degree the renal, nervous, and endocrine mechanisms through which arterial pressure is maintained. As a result, the kidneys retain excess salt and water; the volume of extracellular liquid, including the plasma, expands; and the systems that limit the blood volume are overridden.