events as blood enters the atria and leaves the
ventricles
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? The events includes
1. Changes in the pressures in different chambers of the heart
2. Changes in the volume in different chambers of the heart
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3. Changes in the aortic, pulmonary arteries4. Heart sounds
5. ECG changes
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Cardiac Cycle0.5 sec
0.1 sec
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0.7 sec
0.3 sec
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Phases of Cardiac CycleVentricular Systole
? Isovolumetric contraction
? Rapid ejection
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? Slow ejectionPhases of Cardiac Cycle
Ventricular Systole
? Isovolumetric contraction
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? Rapid ejection? Slow ejection
Ventricular Diastole
? Isovolumetric relaxation
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? Rapid filling? Slow filling (Diastasis)
? Filling d/t Atrial Systole
Phases of Cardiac Cycle
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Ventricular Systole
? Isovolumetric contraction
? Rapid ejection
? Slow ejection
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Ventricular Diastole
? Isovolumetric relaxation
? Rapid filling
? Slow filling (Diastasis)
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Start
? Filling d/t Atrial Systole
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Cardiac Cycle
Phases
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Cardiac CyclePhases
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Cardiac CyclePhases
Cardiac Cycle
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Phases
Cardiac Cycle
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Phases
Phases of Cardiac Cycle
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Ventricular Systole? Isovolumetric contraction
? Rapid ejection
? Slow ejection
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Ventricular Diastole? Isovolumetric relaxation
? Rapid filling
? Slow filling (Diastasis)
? Filling d/t Atrial Systole
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Ventricular Systole? Isovolumetric contraction phase
? Rising ventricular pressure results in closing of AV valves (1st
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heart sound ? "lubb")
? Ventricles are contracting but no blood is leaving
? Ventricular pressure not great enough to open semilunar valves
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? Ventricular ejection phase opens semilunar valves? Ventricular ejection phase
? Semilunar valves opens
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? Rapid Ejection (70% blood)? Slow ejection (30% blood)
Ventricular Diastole
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? Isovolumetric relaxation? volume does not change as ventricles relax, pressure
drops and AV valves open
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? Ventricular fil ing
? Rapid ventricular filling:as blood flows from full atria
? diastasis: as blood flows from atria in smaller volume
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? atrial systole pushes final 20-25 ml bloodPhases of Cardiac Cycle
Ventricular Systole
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Duration (approximate)? Isovolumetric contraction
0.05 sec
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? Rapid ejection
0.10 sec
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? Slow ejection0.15 sec
Ventricular Diastole
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? Isovolumetric relaxation0.10 sec
? Rapid filling
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0.10 sec
? Slow filling (Diastasis)
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0.20 sec? Filling d/t Atrial Systole
0.10 sec
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Normal Volume of Blood in Ventricles
? Atrial systole pushes final 20-25 ml blood (20%)
? After atrial contraction, 110-120 ml in each ventricle
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(end-diastolic volume)
? Contraction ejects ~70 ml (stroke volume output)
? Thus, 40-50 ml remain in each ventricle (End
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systolic volume)
? The fraction ejected is then ~60% (ejection fraction)
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A Simple Model of Stroke Volume
Ventricular Pressures
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? Blood pressure in aorta is 120 ? 80 mm Hg
? Blood pressure in pulmonary trunk is 25 ? 8 mm Hg
? Ventricular pressure usually not increases during diastole
? Right Atrial pressure changes reflected in Jugular vein
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Jugular venous pulse waves
Jugular venous pulse waves
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? a-wave is due to atrial systole which causes increase in
the intra-atrial pressure
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? C-wave occurs during the isometric contraction of theventricles due to bulging of the tricuspid valve
? V-wave is due to accumulation of blood during late part
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of the ventricular systole or protodiastolic phase and
isometric relaxation of the ventricles
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Jugular venous pulse waves
? X-wave is due to downward displacement of the A-V
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valve (tricuspid valve) and the AV ring during maximumejection phase of ventricular contraction
? Y-wave is due to opening of the AV valve (tricuspid
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valve) during maximal ventricular filling phase
Jugular venous pulse waves
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? "a-c" interval measures the time of conduction of the cardiac impulsefrom the right atrium to the ventricles
? The a-c interval corresponds to the P-R interval of the ECG
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? The "a-c" interval is prolonged in cases of delayed conductivity in the
AV bundle which is an early sign of heart block
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? In partial heart block, the number of "a" waves is greater than thenumber of the "c" or "v" waves.
? In atrial fibril ation, the "a" wave is absent.
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Putting it all together!
Putting it all together!
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Thank You