CAM201 Lecture Notes - Lecture 4: Systolic Geometry, Valvular Heart Disease, Heart Valve

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8 Jun 2018
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Basics of the Cardiac Cycle
Contraction and relaxation cause cyclic alterations in the pressures within the heart chambers.
Pressure differences between heart chambers lead to the flow of blood between chambers
and also the major blood vessels in contact with the heart.
The flow of blood through the heart is unidirectional because of the presence and properties
of the heart valves.
There are 5 basic steps to a cardiac cycle
1. Diastole - Relaxation and Filling
Muscle:
Atria relaxed
Ventricles relaxed
Pressure:
Ventricular pressure is less than atrial
pressure
Ventricular pressure is much less than
pulmonary artery and aortic pressure
Valves
AV valves open
Semilunar valves closed
Blood flow:
Blood flows passively into both atria and
ventricles down the pressure gradient
High flow rate because of low resistance
2. Atrial Systole/Ventricular Diastole
Muscle:
Atria contract
Ventricles relaxed
Pressure:
Ventricular pressure is less than atrial
pressure
Ventricular pressure is much less than
pulmonary artery and aortic pressure
Valves
AV valves open
Semilunar valves closed
Blood flow:
Active blood flow into ventricles as atria
contract
3. Ventricular Systole - Isovolumic Contraction
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Muscle:
Atria relax
Ventricles contracting
Pressure:
Ventricular pressure is greater than atrial
pressure
Ventricular pressure is rising but still lower
than pulmonary artery and aortic pressure
Valves
AV valves snap shut
Semilunar valves closed
Blood flow:
Ventricular volume does not change, ie. No
blood flow (isovolumic)
4. Ventricular Systole - Ejection
Muscle:
Atria relax
Ventricles contracting
Pressure:
Ventricular pressure is greater than atrial
pressure
Ventricular pressure is greater than
pulmonary artery and aortic pressure
Valves
AV valves snap shut
Semilunar valves open
Blood flow:
Blood ejected into pulmonary artery and
aorta from both left and right ventricles
The volume of blood ejected = stroke
volume
Atria begin to fill passively with blood
5. Ventricular Diastole
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Muscle:
Atria relax
Ventricles relaxing
Pressure:
Ventricular pressure is greater than atrial
pressure
Ventricular pressure has fallen below
pulmonary artery and aortic pressure
Valves
AV valves closed
Semilunar valves closed
Blood flow:
Ventricular volume does not change, ie. No
blood flow (isovolumic)
Then the cycle restarts
Wiggers Diagram
The diagram illustrates the coordinated variation in each factor/values as the heart beats
The Wiggers diagram contains:
o Details of pressure changes in the LEFT side of the heart
o Details of volume changes in the LEFT side of the heart
o An ECG
o Phonocardiogram (heart sounds)
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Document Summary

Blood flow: blood flows passively into both atria and ventricles down the pressure gradient, high flow rate because of low resistance, atrial systole/ventricular diastole. Pressure: ventricular pressure is less than atrial pressure, ventricular pressure is much less than pulmonary artery and aortic pressure. Blood flow: active blood flow into ventricles as atria contract, ventricular systole - isovolumic contraction. Pressure: ventricular pressure is greater than atrial pressure, ventricular pressure is rising but still lower than pulmonary artery and aortic pressure. Blood flow: ventricular volume does not change, ie. no blood flow (isovolumic, ventricular systole - ejection. Pressure: ventricular pressure is greater than atrial pressure, ventricular pressure is greater than pulmonary artery and aortic pressure. Blood flow: blood ejected into pulmonary artery and aorta from both left and right ventricles, the volume of blood ejected = stroke volume, atria begin to fill passively with blood, ventricular diastole.

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