Lecture 11 Cardiac Cycle Flashcards
Starting from isometric/isovolumic contraction, what is the sequence of closing and opening of valves in the cardiac cycle?
VENTRICULAR PRESSURE CURVE:
From beginning of isovolumic contraction (when ventricles are pumping - remember both ventricles pump at the same time!): Mitral Valve Closes Aortic Valve Opens Aortic Valve Closes Mitral Valve Opens Mitral Valve Closes
By stages: REMEMBER DURING IC AND IR = all 4 valves are closed.
- Isovolumic contraction: Mitral valve closing to Aortic Valve opening
- Systole: Aortic valve opening to Aortic valve closing
- Isometric Relaxation: Aortic valve closing to Mitral valve opening
- Diastole: Mitral valve opening to Mitral valve closing
Why is it important for the cardiac conduction system to pause at the AV node?
Depolarization pauses at the AV node to allow for VENTRICULAR FILLING!
What is the hangout interval (when the pressure gradient is reversed = starts to fall) also known as?
protodiastole
*the heart has started to rapidly eject blood so it takes a few miliseconds for the aortic valve to close
What is the pressure in the heart (LVED) at the end of diastole?
4-12 mm Hg
*Because the heart has been filling the pressure has gone up a bit
Is diastole almost twice as long as systole and why?
Yes! To allow for filling the heart with blood
What is the dichrotic notch in aortic pressure and what causes it?
a high frequency oscillation in the aortic pressure
caused by the reverberation of the aortic valve closing
The Wigger’s Diagram (Cardiac Cycle Diagram) shows what pressures, volumes and sounds?
aortic pressure ventricular pressure atrial pressure ventricular volume heart sounds (phonocardiogram) EKG
What happens to the aortic pressure curve i.e. mean pressure and pulse as blood goes from the Aorta to arteries, arterioles, capillaries and veins?
Mean Pressure goes down (bec/ of reflected waves), lose high frequency components and you get higher highs and lower lows and
Pulse widens for 2-3 generations
What factors influence arterial pressures?
changes in:
- stroke volume
- heart rate
- aortic distensibility
- peripheral resistance
- ejection velocity
If you have a low HR but the same CO, how does your Stroke Volume and Pulse Pressure compare to HR?
SV is high
PP is high
What is pulse pressure?
Systolic Pressure - Diastolic Pressure
If its harder to eject blood/takes a longer time to eject blood, then your pulse pressure will be lowered!
What is peak systolic pressure for systemic circulation and peak systolic pressure for the pulmonary artery?
Systolic Pressure = can reach up to 120 mmHg
Pulmonary Artery systolic pressure = can reach up to 25 mmHg
What is protodiastole aka “hangout interval”?
the interval between Aortic valve closing and crossing of Aortic pressure and Left ventricle pressure curves
What is the c wave of atrial pressure?
first upward deflection of the atrial pressure during isometric contraction which is caused by bulging of AV valves
What is the v wave of atrial pressure?
LA pressure falls SLOWLY
*remember when LVP falls below atrial pressure, mitral valve opens
What is the a wave?
atria contraction caused by atria depolarizing (P wave of EKG)
What is the ejection fraction?
ratio of SV to EDV
In normal heart should be at least 1/2
What is residual volume?
volume of blood remaining in the heart after systole
What is systolic reserve capacity?
volume of blood remaining the heart after systole that could be pumped during a maximal contraction
What type of filling does atrial contraction produce?
active ventricular filling = 20% of all filling in the resting state (so not much represents active filling) but can be greater with rapid heart rates
When the mitral valve opens at the beginning of diastole, what type of filling is occurring?
Rapid passive ventricular filling
What is the diastolic filling pattern?
RAPID passive ventricular filling –> SLOW passive ventricular filling (= DIASTASIS) –> atrial contraction produces ACTIVE filling
