Lecture 10: The heart as a pump Flashcards
Describe the phases of the cardiac cycle:
Atrial systole Isovolumetric contraction Ejection - Rapid ejection - Reduced ejection Isovolumetric relaxation Filling - Rapid filling - Reduced filling
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Explain
What is isovolumetric contraction?
The phase between start of ventricular systole and the opening of the semilunar valves.
- Sharp rise in pressure, no change in volume. (Isometric contraction at this stage, isotonic during ejection)
What does the onset of isovolumetric contraction co-incide with?
- Peak of R wave
- S1
- Earliest rise in ventricular pressure
What can ventricular ejection be divided into?
Early: Rapid ejection phase
Later: Reduced ejection phase
What are the three characteristics of the ejection phase?
- Sharp rise in ventricular and aortic pressure (b/c valves open) -> Terminated at the peak of pressure wave
- Dec. ventricular volume
- Inc. aortic blood flow
Describe the reduced ejection phase
The flow from the aorta is greater than the flow from the ventricle therefore the pressure in the aorta declines.
- Reversal of the ventricular-aorta pressure gradient duing continuous LV flow.
- Decceleration of the flow from the LV into the aorta.
Describe isovolumetric relaxation:
- Closure of aortic valve produces insura (notch) on the P curve (and S2)
- Period b/w semilunar closure and AV opening
- Rapid decrease in P w/o change in volume
Describe the rapid filling phase: (passive)
- AV valves open and blood flows into ventricles (pressure gradient)
(reduced filling phase follows (Diastasis)
Describe diastasis: (passive)
- Slow ventricular filling
- (Follows rapid filling phase)
- Gradual rise in atrial and venous pressures as volume increases.
(length of passive filling determined by heart rate)
Describe atrial systole:
- Occurs just after P wave
- Completes ventricular filling
- Contributes to ventricular filling dependant on HR
What are venous pulse waves?
Atrial P waves
Describe the venous pulse waves:
a wave - Reterograde pressure pulse in jugular when atria contract
c wave - during early phase of ventricular systole
v wave - gradual pressure increase during reduced ejection and isovolumic relaxation
What does JVP show us?
Indirect measure of central venous pressure (venous hypertension)
(raised right atrial pressure results in distension of internal jugular vein)
What are cardiac causes of raised JVP?
Right sided HF
Tricuspid regurgitation
Constrictive pericarditis
