Ventricular function Flashcards
Stroke volume =
SV=EDV-ESV
Define afterload
Pressure at which the ventricles have to contract against
Describe Frans Starlings law relating to the heart
As EDV increases pressure increases, maximum potential pressure increases, greater stretch, greater stoke volume.
Define inotropic
Force of contraction
Define chronotropic
Relates to heart rate/ rhythm
Does an increase in heart rate increase or decrease the inotropic state
Increase
What effect does increase in HR have on SV and why
It decreases it due to reduced filling time. This effect is only evident at high rates
Describe why the left and right sides of the heart pump essentially the same volumes over time
Because the cardivascular system is a closed circuit.
Three mechanisms for altering ventricular performance
Factors affecting preload
Factors affecting afterload
Factors affecting the inotropic state
Factors affecting the HR
Name factors that affect preload
Blood volume Venous tone (vasoactive drugs) Posture Diastolic interval (HR) Atrial contraction Intrathoracic pressure Intrapericardial pressure Ventricular compliance
Name factors that affect afterload
Sytemic pressure (hypertension)
Vasocontricion
Aortic stenosis
Ventricular geometry (wall stress La place)
Factors that effect the inotropic state
ANS Catecholamines Force-frequency relationship AP changes Cardiomyopathy Positive inotropic drugs (digitalis) Cardiac depressant drugs External ion concentrations
Factors that affect the HR
Neural, ANS
Reflexes
Higher centres
Circulating catecholamines
Ejection fraction formula
Ejection fraction = EDV-ESV/EDV *100
What is a method for determining ejection fraction
Echocardiography
