Flashcards in Physiology of Heart Failure Deck (17):
What determines cardiac output, CO = ?
CO = HR x SV
How does contractility, preload and afterload affect SV?
contractility - inc SV
preload - inc SV
afterload - dec SV
How is afterload estimated?
by systolic ventricular (arterial) pressure
True or False: Contractility is independent of the preload and afterload.
What is the SV = ?
SV = EDV - ESV
What is the ejection fraction, EF = ? What is it normally?
EF = SV/EDV
What is compliance = ?
compliance = change in volume/change in pressure
Describe total tension in heart, active tension and passive tension.
Total tension = tension during systole
Passive tension = tension during diastole
Active tension = total tension - passive tension
Describe the Frank-Starling mechanism and how it relates to heart failure.
The force of contraction increase with increase in preload (muscle stretch) to an optimum point, then it decreases.
In heart failure, SV is dec so EDV is increased. This inc in EDV (inc preload) stretches the myocardium and generates a greater force of contraction, which increases the SV. This is a temporary compensatory mechanism in heart failure.
At lower work rates, which mechanism (Frank-Starling or contractility) has a greater contribution to increasing stroke volume? What about at higher work rates?
At lower work rates, Frank-Starling mechanism has the greatest contribution to increasing stroke volume. At higher work rates, contractility has the greater influence on increasing stroke volume.
What is the effect of increased contractility on SV?
It will increase SV at every level of EDV.
What happens to contractility in heart failure?
What is normal JVP (ASA?) How do you calculate RA pressure from JVP?
normal JVP is <4-5 cm ASA
JVP + 5 cm = RA pressure
How do you differentiate the JVP from carotid pulse? ** EXAM
varies with respiration
varies with position
changes with abdominal compression
What are the seven events of the cardiac cycle?
1 - atrial systole
2 - isovolumetric ventricular contraction
3 - rapid ventricular ejection
4 - reduced ventricular ejection
5 - isovolumetric ventricular relaxation
6 - rapid ventricular filling
7 - reduced ventricular filling or diastasis
What is the effect of preload on EDV?
inc preload inc EDV