Role of Autonomic Hormones on Left Ventricular Performance Continuously Analyzed by Electronic Computers

Ventricular responses during spontaneous activity by intact dogs have been studied by using electronic computors to continuously analyze ventricular function in terms of various parameters, including effective ventricular pressure, changes in left ventricular circumference or diameter, rate of change in ventricular dimensions, myocardial "power," myocardial "stroke work," "eumulative work" per unit time and heart rate. Simultaneous recordings of these various factors permit characterization and direct comparison of the nature and sequence of left ventricular responses during infusion of autonomic hormones, spontaneous activity or exercise. Intravenous infusion of catechol amines in "physiologic doses’ produces changes in ventricular performance which differ significantly from those observed during exercise, particularly with reference to heart rate. The left ventricle appears to be directly influenced by neural reflexes, some of which are probably initiated by higher centers of the nervous system.