Intrinsic heart function and food intake

The author reviews the haemodynamic changes in response to exercise, autonomic nervous blockade and food intake. Left ventricular (LV) volume changes are most pronounced during mild exercise, whereas an increase in heart rate is the primary determinant for the increase in cardiac output during mild to heavy exercise. After autonomic blockade the heart possesses intrinsic mechanisms to maintain cardiac output during submaximal exercise. LV en diastolic dilatation results in a preserved stroke volume despite reduced contractility. At rest cardiac output increases postprandially mostly because of a greater stroke volume accomplished by LV end diastolic dilatation, whereas heart rate is only slightly increased. These changes are unique to humans, and are thought to take place secondary to the action of vasoactive peptides from the gastrointestinal tract involved in digestion. The LV volume changes are minimized after autonomic nervous blockade. During exericise cardiac output is also higher after food intake due to a rise in both stroke volume and heart rate, but only in the innervated heart. Thus, most of the haemodynamic changes recorded after food intake are under the influence of the autonomic nervous system.