CARDIO- Cardiac Cycle Flashcards
what is the cardiac cycle
describes the movement of blood through the heart during one heartbeat
comprises of relaxation of the ventricles (diastole) and contraction of the ventricles (systole)
what are the general principles of the cardiac cycle
blood flows from areas of high pressure to areas of low pressure unless flow is blocked by a valve
valves open and close depending on pressure changes in the chambers
events on the right and left side of the heart are the same
pressure is lower on the right side
outline the flow of blood through the heart
venous return from great veins - right atrium tricuspid valve right ventricle pulmonary arteries lung circulation pulmonary veins left atrium bicuspid valve left ventricle aortic semilunar valve aorta systemic circulation
outline chamber and volume changes in the heart
1- ventricular filling / atria contraction - higher pressure in atria >ventricles - bi / tri valves open
- blood enters ventricles
- atrial contraction - extra filling
2- isovolumetric contraction
- higher pressures in ventricles > atria
- bi / tri valves are closed
- ventricle contraction
3- ejection
- higher pressure in ventricles > aorta / pulmonary artery
- valves open
- blood flows out of heart
- blood enters atria
4- isovolumetric relaxation
- higher pressure in aorta/pulmonary artery >ventricles
- valves close
- ventricle relaxes, expands and is ready to receive
what are heart sounds
vibrations induced by the closure of cardiac valves / vibrations in ventricular chambers / turbulent blood flow through valves
describe 4 heart sounds
s1- lubb - closure of tricuspid valves at the beginning of ventricular systole
s2- dubb - closure of aortic / pulmonary valves at the beginning of ventricular diastole
s3- occasional - turbulent flow into ventricles detected near the end of 1/3 diastole - common in young people
s4- pathological in adults - forceful atrial contraction against a still ventricle - potentially abnormal
describe the pressure changes in the left ventricle during the cardiac cycle
atrial systole - low pressure
ventricular systole - sharp increase in pressure and then decrease in pressure (dome shaped on graph)
ventricular diastole - pressure is low again once mitral valve open
describe the changes in left ventricular volume throughout the cardiac cycle
high in atrial systole - slow increase
mitral valve closes
ventricular systole decrease in volume (starts rapid then slows)
aortic valve closes
ventricular diastole - rapid increase that slows
why is the left ventricle pressure-volume loop an important consideration
work (mechanical energy to increase pressure and movement of blood) = change in ventricular pressure x change in volume
it relates to the amount of energy consumption used to produce stroke volume
area inside the loop = amount of stroke work done
EDV- ESV = stroke volume ~ 80ml
how is the left ventricular pressure loop associated with valve disease
valve stenosis - narrowing of valve = reduced blood flow through it =
aortic stenosis - aortic valve doesn’t fully open - build up of pressure in left ventricle - poor ejection
mitral stenosis - mitral valve doesn’t fully open - poor filling of left ventricle - low EDV - poor SV
describe the pressure changes in the right atria
during diastole - slow rise then rapid rise - then rapid decrease
av valve close
ventricular systole - rapid decrease then rapid increase
then slight decrease - further increase then rapid decrease
what is the clinical relevance of the atrial pressure change
right sided heart failure - poor ejection from right ventricle
more blood volume remains in the right ventricle
increased blood pressure in right ventricle
raised jugular venous pressure - increased height of venous distension
