The document discusses three key determinants of cardiac output: preload, afterload, and contractility. Preload refers to the presystolic stretch of the heart and is reflected by the end-diastolic pressure and volume. Afterload is the pressure the left ventricle must overcome during systole and is often represented by systolic pressure. Contractility determines the strength of the heart's contraction and can be measured by the left ventricular ejection fraction.

1. Cardiac
PRESSURE-VOLUME LOOPS
Dr.Syed Shaheer Haider
PGT Anesthesiology

2. Recalling…
Determinants of Cardiac Output:
1. Preload
2. Afterload
3. Contractility (Inotropy)

3. Recalling…
Preload: It is the presystolic stretch.
Frank-Starling law states that greater the
preload, the greater will be cardiac
output.
End-Diastolic volume is reflected in End-
Diastolic pressure LVEDP=LA pressure.
Pulmonary artery wedge
pressure(PCWP) = LA pressure = PA
diastolic pressure

4. Recalling…
Afterload: Pressure that needs to
overcome for left ventricle (Systole)
Defined as wall stress during systole
Laplace formula:
Wall Stress ð = Pressure x Radius/2h ( Thickness)
Systolic pressure is often used to
denote afterload

5. Recalling…
Contractility: That determines the
strength of contraction
LVEF = Stroke volume
End Diastolic volume
(or)
LVEF = End Diastolic volume – End Systolic volume
End Diastolic Volume

6. Basic Loop