1. What are the events that occur during one heart beat?
   Oxygen-poor blood (shown in blue) flows from the body into the right atrium.    Blood flows through the right atrium into the right ventricle.   
                                
Cardiac Cycle: one complete heartbeat, consisting of the contraction/relaxation of both atria, followed by the contraction/relaxation of both ventricles. The average duration is 0.8 sec.
                                
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What are the events that occur during one heart beat?

2. The Cardiac Cycle: Definitions
Systole: phase of myocardial contraction (atrial systole, ventricular systole); during systole, the pressure in a chamber is elevated and blood is ejected
Diastole: phase of myocardial relaxation; during diastole, the pressure in a chamber falls and the chamber fills with blood
Systole
Diastole

3. Cardiac cycle points to remember:
1. The purpose of the myocardium is to contract to provide pressure for the ejection of blood (systole) and to relax to reduce pressure and allow filling (diastole).
2. Blood moves from regions of high pressure to regions of low pressure.
3. The contraction of the myocardium is coordinated by the cardiac conduction system.
4. The valves of the heart (atrioventricular and semilunar) ensure that blood moves in a forward, not backward, direction.
The cardiac cycle

4. 75 Event Value # cardiac cycles/minute
Duration of one cardiac cycle second
Duration of sec
Duration of atrial diastole
Duration of ventricular systole
Duration of sec.
Duration of cardiac quiescence (the atria and ventricles are in diastole at the same time) 75
atrial systole
0.7 second
0.3 second
ventricular diastole
0.4 second
Note: the events of the cardiac cycle are traditionally described in terms of the left heart. Pressure changes occurring in the right heart are 1/5th as great as the changes in the left heart

6. The Cardiac Pressure Curve
End Diastolic Volume (EDV)
The volume of blood received by a ventricle during the period of ventricular filling
End Systolic Volume (ESV)
The volume of blood remaining in a ventricle after the period of ventricular ejection

7. Early Ventricular diastole
Ventricle Diastole
Ventricular Systole
Early Ventricular diastole
Passive ventricular filling
Active ventricular filling
Period of isovolumetric contraction
Period of ejection
Period of isovolumetric relaxation
Blood flow
From atrium into ventricle
Contraction of atrium pumps additional 20-25% of blood
Ventricles begin to contract – no volume change
Ventricle continue to contract – blood ejected into aorta
Pressures
Atrial>ventricular
Ventricular >aorta
Atrial starting to rise
Valve state
A-V open (pressure in atrium greater than pressure in ventricle
Semilunar closed (pressure in aorta > pressure in ventricle
A-V open
Semilunar -
A-V closes (pressure in ventricle is greater than atrium)
A-V closed (pressure in ventricle>pressure in atrium
Semilunar opens– why?
ECG
Pre-P wave
P-wave
QRS
T-wave
Heart Sound
Comments
End Diastolic volume
Period of isovolumetric contraction – all valves closed, ventricular volume does not change (an isometric contraction?)
End-systolic
Volume
Ventricular pressure > atrial
Why? Atrial systole
Why? Atrial pressure > than ventricular pressure
Closed -pressure in aorta is still > than ventricle
Closed -pressure in aorta > than ventricle
Pressure in ventricle is now > than aorta
none
none
1st heart sound
none
The volume of blood received by a ventricle during the period of ventricular filling
The volume of blood remaining in a ventricle after the period of ventricular ejection

8. Mid Ventricular Diastole a. The atria and ventricles are in diastole
b. Atrial pressure is ventricular pressure
Thus, blood moves from atria into ventricles through open AV valves
Note: the ventricles receives about of its final blood volume during this time
Late Ventricular Diastole
the atria contract and eject the remaining volume of blood into the ventricles
Note: the ventricles receive the remaining blood during atrial systole
greater than
75%
25%
The arteries during this entire time period are pressure as blood circulates to smaller vessels
losing

9. Ventricular Systole Ventricular pressure as the ventricles contract
When ventricular pressure is greater than atrial pressure, the AV valves
When ventricular pressure is greater than arterial pressure, the semilunar valves and blood is ejected into the arteries
close
open
Isovolumetric Period of Contraction:
period of time, during ventricular systole, after the AV valves close but before the semilunar valves open, when ventricular volume remains unchanged

10. Early Ventricular Disatole
Ventricular pressure falls during ventricular diastole
When ventricular pressure is less than arterial pressure, the semilunar valves close
When ventricular pressure is less than atrial pressure, the atrioventricular valves open ; the ventricles begin to fill
Isovolumetric Period of Relaxation
Period of time, during ventricular diastole, after the semilunar valve closes but before the AV valve opens, when ventricular volume remains unchanged

11. A Few Other Things .. Dicrotic Notch:
A brief rise in arterial pressure that results from arterial blood rebounding off of newly closed semilunar valves
End Diastolic Volume (EDV)
The total volume of blood that a ventricle receives during its filling period
End Systolic Volume (ESV)
The total volume of blood left in a ventricle after ventricular contraction
Stroke Volume (SV)
The total volume of blood that ejected into arteries as a result of ventricular contraction

12. There are two easily and consistently heard heart sounds:
Normal valves have two characteristcs:
1. Unimpeded flow Unidirectional flow
First Sound (S1) Second Sound (S2)
Generated By closure of the closure of the
Sounds like “lub” “dup”
When heard at the beginning of ventricular at the beginning of ventricular
semilunar valves
AV valves
systole
diastole

13. Valve Abnormalities Stenosis:
a significant amount of pressure must be generated to eject blood though a narrowed valve
this can lead to:
1. Increased residual volume of blood in a chamber
2. Cardiac cell hypertrophy
3. Low pulse pressure
A narrowed valve
Rheumatic mitral stenosis: note thickened leaflets and shortened chordae
Calcification of the aortic semilunar valve

14. Note the turbulance (red spirals) of the blood as it flows through the stenotic aortic semilunar valve
It is the turbulance that creates the mumur

15. At which point in the cardiac cycle would you expect to hear a murmur associated with
Stenosis of the mitral valve?
b. Stenosis of the aortic semilunar valve?
Answer choices are:
Ventricular diastole
Ventricular systole
Ventricular diastole
Ventricular systole

16. Insufficiency (Incontinence):
This can lead to:
1. The backward flow of blood
2. Increased volume of blood in the affected chamber
3. Cardiac cell hypertrophy
4. Low pulse pressure
A valve that does not close properly
Ruptured chords – mitral valve prolapse secondary to a Haemophilus infection

17. At which point in the cardiac cycle would you expect to hear a murmur associated with
Insufficient mitral valve?
Insufficient aortic semilunar valve?
Answer choices are:
Ventricular diastole
Ventricular systole
Ventricular systole
Ventricular diastole

18. Causes of valve abnormalities include:
Coronary atherosclerosis (papillary muscle dysfunction)
Rheumatic fever (most common cause, mitral valve)
Autoimmune diseases
Congenital malformations of valves
Connective tissue defects (eg, Marfan’s syndrome)
Aging (calcification)