Effects of High Hydrostatic Pressure on the Cardiac Muscle Part I. On the Isolated Frog Heart

When high hydrostatic pressure was applied to isolated frog heart, following changes were observed on the cardiac action: 1) At relatively low pressure, heart rate increased, but at moderate high pressure, it decreased. 2) There occurred no change of conduction time, namely P-Q interval. 3) Upon appling pressure, the amplitude of action potential of ventricle muscle, i.e. the height of R wave augumented.