Factors affecting cardiac output
Since the CO is defined by SV and HR, changes in either of these factors can alter the cardiac output.
Factors affecting stroke volume:
- Preload, which depends on venous tone and blood volume
- Contractility (or inotropy), which depends on autonomic innervation and hormones
- Afterload, which depends on ventricle outflow tract resistance and/or arterial vascular resistance
An increase in preload or contractility/inotropy will result in an increased stroke volume; the fvia increase in the EDV, the latter mediated by a decrease in ESV. An increase in afterload will evoke a decrease in stroke volume via an increase in ESV.
Factors affecting heart rate:
Autonomic innervation and hormones are the main determinants of heart rate.