Dynamic basis for sympathetic cardiac augmentation

Analysis of optically recorded cardiovascular pressure pulses during sympathetic stimulation of the heart reveal a multiplicity of direct influences on the myocardium. An increased rate of pressure rise and pressure fall along with a shortened duration of contraction and relaxation indicates more synchronous myocardial contraction and a direct sympathetic influence on conductile and contractile tissues. Heart rate changes denote the well known action on nodal tissue. A decreased duration of contraction and relaxation significantly increases time available for cardiac filling, and thus permits augmented cardiac ejection without necessitating change in end-diastolic volume. The increased force and shortened duration of contraction and relaxation during sympathetic stimulation may be present even in the absence of increased ejection and augmentation of arterial pressure pulses.