VENOUS PRESSURE IN CARDIAC DECOMPENSATION

The most important development in recent years in cardiodynamics is the discovery of the relationship between venous pressure and heart activity. The older conception, based largely on theoretical deductions from the physical conditions of the circulation and on data derived from studies of mechanical circulation schemata, was that the heart output modified venous pressure by varying the rapidity with which blood was taken from the veins and pumped into the arteries. In this conception it is clear that cardiac activity is the primary factor, and changes in venous pressure are the result. In the modern conception the order of these is reversed, and it is now recognized that the venous pressure is the main factor in regulating cardiac activity. An increased venous return causes increased cardiac output; a reduced return with a lower pressure tends to result in reduced cardiac activity. There is thus a self-regulating mechanism which tends to