Cardiac Output — Contractility

Myocardial contractility

• Ability of myocardium to contract (or myofibrils to shorten) against a given afterload, with a given preload

dP/dT

• Change in pressure / change in time
• Measure of contractile force exerted by the myocardium at the start of systole
• One of the oldest measures of global myocardial contractility
• Measured via doppler analysis of mitral regurgitant jet
• Limited by
  • Requirement for MR jet
  • Affected by preload, afterload and contractility

ESPVR

• Line created with a series of LV pressure volume loops where preload was varied with a fixed afterload. The point at which aortic valve closure occurred was plotted.
• This is a surrogate for contractility on the pressure-volume loop.
• Invasive and impractical

EF

• Fraction of end-diastolic volume which is ejected (stroke volume / end-diastolic volume)
• 60% in normal heart (70ml/120ml)

Sakurai 2016

Answer by Sakurai