4.4 Cardiac Haemodynamics Flashcards
(11 cards)
What are the main functions of the heart
To maintain blood pressure and blood flow
Describe the 3 components of arterial blood pressure
systolic blood pressure - the highest pressure in the arteries during ventricular systole, represents the force exerted on artery walls when the heart pumps blood
diastolic blood pressure - the lowest pressure in the arteries during diastole, represents the resistance of blood vessels when the heart is at rest
‘mean’ blood pressure - average arterial pressure throughout 1 heart cycle,
How does the arterial pulse occur
The arterial pulse can be felt and it is intimately related to the mechanical events occurring in the cardiac cycle. During systole, blood is ejected into the arteries, generating a pressure wave creating a pulse
What factors influence arterial pulse
heart related factors (e.g stroke volume, heart rate, heart rhythm)
artery related factors (e.g elasticity of vessels, peripheral resistance, blood volume)
systemic factors (e.g body position, temperature, metabolism, drugs)
What can general blood flow be equated to
Blood flow = Cardiac Output = Heart Rate x Stroke volume
How is blood flow through a specific organ determined
flow through an organ = change in pressure/resistance
This is the concept driving Starlings law of the heart
What is Starling’s law of the heart
the greater the stretch of the ventricle (ventricular filling) during diastole, the greater the stroke work achieved during systole (greater force of contraction)
-The starling law is a function of the length tension relation in muscle (does not require neural regulation.
What is stroke work and how is it calculated
Stroke work represents the force of contraction the heart generates to eject blood during systole.
change in left ventricular pressure x Stroke volume
What are 2 ways that Starlings Law can be portrayed
through pressure volume relationship graphs and through Starlings Curves (plotting pressure against time)
What is preload
degree of stretch of the ventricular muscle fibers at the end of diastole (before the heart contracts) as the blood fills the chamber
What is afterload
the resistance the heart has to overcome to eject blood during systole.
