Cardiac cycle Flashcards
What is a Wiggers diagram?
Shows changes in pressure, volume, electrical activity, sound
during the cardiac cycle
How does a Wiggers diagram of the left side of the heart compare to that of the right side of the heart?
Very similar
except left side is at higher pressures
What are the phases of the cardiac cycle?
Systole
Diastole
What is systole?
Contraction and ejection of blood from ventricles
What is diastole?
Relaxation and filling of ventricles
What are the phases of systole?
Isovolumetric contraction
Rapid ejection
Reduced ejection
What are the phases of diastole?
Isovolumetric relaxation
Rapid filling
Reduced filling
Atrial contraction
What happens in atrial contraction?
P wave on ECG - atrial depolarisation
A wave in atrial pressure - atrial pressure increases
EDV in ventricular volume - ventricular volume increases to EDV
Atrial contraction accounts for what percentage of ventricular filling?
10%
What is EDV?
End diastolic volume
volume in left ventricle at end of diastole
What is the average EDV?
120ml
What happens in isovolumetric contraction?
QRS complex in ECG - ventricular depolarisation
Increase in ventricular pressure - ventricle contracting
S1 sound - closure of mitral valve (tricuspid valve too) as intraventricular pressure exceeds atrial pressure
C wave in atrial pressure - atrial pressure increases due to closure of mitral valve, slight inversion into atria
What is meant by isovolumetric in isovolumetric contraction/relaxation?
Both valves are closed
no change in volume of blood in left ventricle
What happens in rapid ejection?
Increase in ventricular pressure - ventricle contracting
Aortic valve opens - intraventricular pressure exceeds aortic pressure
Increase in aortic pressure - filling with blood from ventricle
Decrease in ventricular volume - ventricle ejecting blood into aorta
X descent in atrial pressure - atrial pressure decreases as base of atria pulled down
What happens in reduced ejection?
T wave on ECG - ventricular repolarisation
Decrease in ventricular pressure - ventricle relaxing
Decrease in aortic pressure - less blood entering it from ventricle, blood begins to leave it
V wave in atrial pressure - atrial pressure increases as it fills with blood from venous return
What hapens in isovolumetric relaxation?
Decrease in ventricular pressure - ventricle relaxing
S2 sound - aortic valve closure as aortic pressure exceeds intraventricular pressure, backflow of blood, valve closes
Dicrotic notch in aortic pressure - increase in aortic pressure, walls of aorta pulled inwards as valve closes
ESV in ventricular volume - end systolic volume, volume of blood in ventricles at end of systole
What is the average ESV?
40ml
What happens in rapid filling?
Mitral valve opens - atrial pressure exceeds intraventricular pressure
Y descent in atrial pressure - atrial pressure decreases as it empties of blood
Increase in ventricular volume - increases as ventricle fills with blood from atria
S3 sound - ventricular filling
How do the ventricles fill with blood from the atria in rapid filling?
Passively
When is the S3 sound normal? When is it a sign of pathology?
Normal in children
Sign of pathology in adults
What happens in reduced filling?
Increase in ventricular volume - slowly increases called diastasis, reach 90% of EDV
What is the pressure in the left atrium?
8-10mmHg
What is the pressure in the LV?
120/10mmHg
What is the pressure in the aorta?
120/80mmHg
What is the pressure in the right atrium?
0-4mmHg
What is the pressure in the pulmonary artery?
25/10mmHg
What is the pressure in the RV?
25/4mmHg
How do the pressures of the systemic and pulmonary circulations compare to each other?
Systemic circulation at high pressure
Pulmonary circulation at low pressure
If the cardiac cycle is 0.9s long, how long is systole? How long is diastole?
Systole = 0.35s
Diastole = 0.55s
A change in heart rate is accommodated by change in duration of systole or diastole or both?
Diastole
