CVS 3 - Mechanical properties of the heart 2 Flashcards
What are the two main phases of the heart beat?
Systole - 2 subparts
Diastole - 4 subparts
State the phases of the cardiac cycle
(Diastole)
1. Slow filling (of atria and ventricules, AV valves opened)
2. Atrial systole
(Systole)
3. Isovolumetric ventricular contraction -
(unchanged volume, all valves closed isometric contraction)
4. Ventricular ejection - semilunar open
(Diastole) - rapid ejection + reduced ejection
5. Isovolumetric ventricular relaxation
6. Rapid filling then back to reduced filling (step 1)
What happens during slow ventricular filling?
Phase: Atria and ventricles relaxed, blood filling ventricles slowly
Valves: AV open, semilunar closed
What happens during atrial systole?
Phase: Atria contract, top off ventricles with blood
Valves: AV open, semilunar closed
P wave: atrial depolarisation
S4: Abnormal heart sound
What happens during isovolumetric ventricular contraction?
Phase: Contraction of ventricles with no change in volume
Valves: AV closes as pressure in ventricles exceeds atria
QRS: Ventricular depolarisation
S1: “lub” from the closure of the AV valves
What happens during ventricular ejection (aka ‘rapid ejection’ + ‘reduced ejection’)?
Rapid ejection:
Phase: Ventricles contract –> pressure within exceeds aortic and pulmonary artery
Valves: Semilunar open –> blood leaves heart
RV contraction pushes tricuspid valve into atrium –> creates wave in jugular vein – “C” wave
The ventricular pressure exceeds the aortic and pulmonary pressures so the aortic and pulmonary valves open and blood rapidly flows out into the aorta and pulmonary artery.
Then reduced ejection:
Phase: Blood flow from ventricles decreases
Valves: SL BEGIN to close because blood starting to flow back from arteries due to lower ventricular pressure
T wave: Ventricular repolarisation
Marks the end of systole. Ventricular pressure begins to fall
T wave on the ECG due to the repolarisation of the ventricles. There are NO heart sounds because none of the valves are shutting.
What happens during isovolumetric ventricular relaxation?
Phase: Atria filling with blood
Valves: SL shut, AV shut (Shutting of atrial valve creates dichrotic notch in atrial reading)
S2: “dub” from SL valves closing
What happens during rapid ventricular filling?
Phase: Ventricles filling
Valves: AV valve open
S3: Abnormal, due to mitral incompetence
What is ejection fraction?
SV/EDV - the proportion of the blood in the heart that is pumped out in one contraction
What ECG change is seen in atrial systole?
P wave - atrial depolarisation
What abnormal heart sound could be heard during atrial systole and what could it be a result of?
S4 - this could be due to tricuspid incompetence, pulmonary embolism or congestive heart failure
How does atrial pressure change during atrial contraction?
Atrial pressure shows a small increase - a wave
Describe the pressure and volume changes that take place during isovolumic contraction.
The valves are all closed so there is no change in volume but the pressure increases dramatically.
What heart sound will be heard during isovolumic contraction?
S1 - closing of the atrioventricular valves
What ECG change is seen during isovolumic contraction?
QRS complex - ventricular depolarisation