Terms related to cardiac performance

Question 1

Preload

Answer 1

The ventricular wall tension at the end of diastole. In clinical terms, it is the stretch on the ventricular fibers just before contraction, often approximated by the end-diastolic volume or pressure.

Question 2

Afterload

Answer 2

The ventricular wall tension during contraction; the force that must be overcome for the ventricle to eject its contents.

Question 3

Contractility (inotropic state)

Answer 3

Property of heart muscle that accounts for changes in the strength of contraction, independent of the preload and afterload. Reflects chemical or hormonal influences on the force of contraction.

Question 4

Stroke volume (SV)

Answer 4

Volume of blood ejected from the ventricle with each systolic contraction.
SV = end-diastolic volume – end-systolic volume

Question 5

Ejection Fraction

Answer 5

The fraction of end-diastolic volume ejected from the ventricle during each systolic contraction (normal range = 55%-75%)
EF = stroke volume / end-diastolic volume

Question 6

Cardiac Output (CO)

Answer 6

Volume of blood ejected from the ventricle per minute.
CO = SV x heart rate

Question 7

Compliance

Answer 7

The ability of a heart chamber to expand and accommodate an increase in blood volume with a given increase in pressure. Intrinsic property of a chamber that describes its pressure-volume relationship during filling. Reflects the ease or difficulty with which the chamber can be filled.

Compliance = change of volume / change of pressure