The heart as a Pump Flashcards
Systole
Chamber contracts and ejects blood
~0.3s
Diastole
Relaxation Phase
~0.5s
*when HR increases, diastole is most affected.
Specific sequence of events
Atrial Systole Isovolumic contraction Rapid Ejection Reduced Ejection Isovolumic relaxation Rapid Filling Reduced filling
Atrial Systole
Soon after the start of the “P” wave; Atrial Depolarization
- top-up ventricles by contracting, completes filling
- Responsible for small increase in A/V pressure and venous volume.
- ‘a’ wave
When is atrial contraction really necessary?
-Contraction not usually necessary as much filling is passive. But at high HR, extra boost is important
Isovolumic Contraction
- Phase between the start of ventricular systole and the opening of the Semilunar valves
- Onset coincides with R-wave peak
- Volume constant but Pressure steeply rises
- c-wave
Rapid Ejection
Semilunar (aortic and pulmonary) valves open
- Rapid increase in aortic flow
- Rapid drop in LV volume
- Atrial pressure drops; base moves towards apex and stretches atria
- Sharp increase in LV and Aortic pressure
Reduced Ejection
-Runoff from aorta to periphery exceeds LV output> aortic P drops > aortic flow drops
- Aortic pressure just > LV pressure
- Forward momentum continues ejection
- Atrial pressure rising (filling from veins)
How much blood is ejected from LV
55%-75%
ESV?
~60mL
Isovolumic Relaxation
- Aortic valve closes due to Pressure-Gradient Reversal. Semilunar also closed
- Incisura
- 2nd heart sound
- Rapid fall in LV pressure, no change volume
- Aortic Pressure remains high
Incisura/dicrotic notch
Small notch of aortic pressure during isovolumic relaxation
-coincides with SL valve closure, as the blood reversal occurs and blood tries to flow back into the LV, there is a increase in Aortic presure due to the elastic recoil of the artery
Rapid FIlling
Major part of V filling
LV rapid increase in LV volume, as blood flows from the atria > ventricles
V pressure is still dropping
3rd Heart sound sometimes heard
Slow filling
Diastasis
- Equalised pressures, slow rise in A and V and venous pressures, and ventricular volume
- Blood returns from peripheral veins > RV and blood from lungs > LV
What are heart sounds?
Due to turbulence cause by valves closing
1st heart sound
Due to AV valves closing. During begining ofisovolumic contraction, rapid P development, opening of semilunar valves and outflow
2nd Heart sound
Due to semilunar valves closing/tensing > resulting vibrations. During Isovolumic relaxation.
Heart Vibrations
Very low frequencies, amplitudes and durations
30-250Hz
Heard via auscultation
Venous pulse/pressure Waves: “a” wave”
Retrograde pressure pulse in jugular when atria contract
Venous pulse/pressure Waves: “c” wave”
during early phase of ventricular systole
Venous pulse/pressure Waves: “v” wave”
gradual pressure increase during reduced ejection and isovolumic relaxation
How to the RV and LV pressures differ
RV pressures are similar to LV, just slightly lower, same with atrial pressures. Also a slight difference in timing.
Same venous pulses
This is due to pulmonary circulation having a lower resistance
Abnormal Heart Sounds:
Regurgitation: Blood leaks back through valve in the wrong direction
Mitral Valve prolapse: mitral valve has “floppy” flaps and doesn’t close tightly. Sometimes causes regurgitation
Stenosis: Valves doesn’t open enough restricting blood flow
Cardiac catherterization
Long thin flexible tube is put in blood vessel in arm, groin or neck and threaded to your heart. Saline filled. Far less invasive
