Cardiac function curve (of Guyton)

• An expression of Frank-Starling curve
  * But NOT the actual Frank-Starling curve
  * Original Frank-Starling curve shows relationship between preload and stroke volume, and is not affected by afterload.
• Dependent on characteristics of the heart
• Shows effects of increases in right atrial pressure (independent variable) on the cardiac output (dependent variable).
• Due to heterometric autoregulation (i.e. autoregulation that is related to length of fibre)
  * cf. homometric autoregulation - independent of fibre length

Shifts in the cardiac function curve

Increased contractility

--> Cardiac function curve moves up

Increased peripheral resistance

--> Cardiac function curve moves down