Events Of The Cardiac Cycle Flashcards
Describe the valves of the heart
AV valve tricuspid - separates right atrium and ventricle
Pulmonary - right ventricle and lungs
AV valve (mitral) bicuspid - left atrium and left ventricle
Aortic valve - left ventricle and aorta
Volume output of rhs and lhs
Volume output = the same
Pressure generated of each side
Why?
LHS: 120 mmHg
RHS: 30 mmHg
Lungs have lower resistance circulation compared to the rest of the body
What determines the direction of flow?
Unidirectional valves
What opens/closes the valves ?
Pressure differences across them
Eg. Higher pressure on lhs
Describe what happens in atrial systole
Rise in atrial pressure (AV valves open) and atria empty blood into ventricles
Aortic pressure decreases
Left ventricular pressure increases as some blood is pushed through and therefore LV volume also increases
When describe what happens in isovolumetric ventricular contraction
Ventricular pressure < aortic therefore aortic valve shut
Aortic pressure still decreasing
Left atrial pressure decreases and ventricular increases, exceeds it, therefore AV valve closes
When is the first heart sound?
When the AV valves closes when ventricular pressure exceeds atrial
Describe ventricular ejection
Ventricular pressure > aortic pressure
Therefore aortic valve opens and blood ejected
This causes aortic pressure to rise (but is still less than ventricular)
LV volume decreases by around 50%
Describe isovolumic ventricular relaxation
Ventricular pressure < aortic pressure therefore aortic valve closes
Ventricular pressure still > atrial therefore AV valve still shut
(Pressure falls but no filling)
Atrial pressure increasing again due to volume of blood entering
Describe ventricular filling
Ventricular pressure < atrial pressure therefore AV valve opens again and blood enters the ventricle
When is the second heart sound?
When aortic valve closes
Ventricular pressure < aortic
When will fluid flow?
When there is a pressure gradient
What is p wave associated with?
Atrial systole
What is QR wave associated with ?
Ventricular depolarisation
What is RS wave associated with?
Isovolumetric ventricular relaxation
What do pulsation of internal jugular vein reflect? And why?
Right atrial pressure changes
No valves present
Describe the ACV wave of jugular venous pulse
A - rise in pressure associated with atrial systole
V - rise in pressure as atrium fills during ventricular systole
C - pressure wave during isovolumetric ventricular contraction causing bulging of AV tricuspid valve
What happens to the JV pulse if there is heart failure on RHS?
higher
Potential 3rd sound of heart
Vibration of ventricular wall filling
4th heart sound
Associated with ventricle filling during atrial systole
When does the aortic valve open and close?
Opens during systole and closes at the start of diastole
Dup
When does the mitral valve open and close?
Opens during diastole closes start of systole
What occurs between lub dup
Systole
What happens between dup and lub
Diastole
What can abnormal heart sounds be caused by ?
Excessive noise causes turbulence
Due to: high flow, flow in different directions
1. Stenosis
2. Leaky/incompetent valve
Stenosis
Narrowing which creates a steep pressure gradient (high flow across valve)
Noise during systole, when valve opens
Eg. Aortic stenosis
Leaky valve
Flow can occur in different directions
Murmur when valve should be closed
Eg. Aortic regurgitation (diastolic murmur)
Shh after dup
