So pressure chambers that are occurring in the ventricle chamber are now being transferred into the aortic chamber. So pressure in the aorta, will now go up to 120 mmHg, since the pressure in the Left ventricle has now reached 120-121 mmHg. Fig. 9 And during this phase, blood is being very rapidly ejected. But nothing lasts forever.

Let’s recap what happened in this phase. The left atria: His humble chamber is still working as a TANK. It is still receiving blood from the lungs. In the beginning, there was an A wave produced by an increase in pressure by atrial contraction. Then in the next phase of Isovolumetric contraction prodced a C wave. Then, the accumulation of venous blood created a continuous V wave. When Ventricle is contracting, the atrium is acting as a reservoir or a TANK.   The left ventricle: pressure has increased past the aortic pressure, so the aortic value is now opened and blood is now being ejected rapidly into the aorta The aorta: The aorta stretches out.

Fig 10 are the various pressure waves up to this point. A wave = atrial contraction pressure C wave = onset of ventricular contraction V wave = Showing how the pressure is increasing by the atrium accumulating venous blood.

Pressure waves

A recap of this PHASE in which the ventricle is injecting blood into the arterial tree, especially the aorta… Elastic compliance of the aorta must not be under-stated, as this elasticity allows for greater pressure and volume into the arterial tree. The ventricle and aorta are acting as the same chamber. This phase is called RAPID VENTRICULAR EJECTION PHASE After that phase The ventricle starts RELAXING.

Next phase time: Next Phase is called: Slow-Ventricular ejection Phase Fig. 11 With the continuation of Ventricular contraction, the mitral value will remain CLOSED. The pressure in the ventricle remains higher than that of the atrium. Still, atrium is acting as a tank. V wave is still continuing to rise Ventricle is still contracting, but since blood is less, the pressure in the ventricle is not as much and is falling. And the aortic valve is still open. No we are entering into the phase when the ventricular pressure is starting to fall. Naturally, the ejection has become slow. Still the intra-ventricular pressure is greater than the aortic pressure, so there is some ejection of blood into the aorta. Pressure is starting to fall in the ventricle and hence pressure in the aorta is starting to fall. As the aortic is an elastic tube, blood is still being pushed into the arterial tree.

NEXT PHASE Fig 12 Left ventricle starts RELAXING It means the onset of ventricular Diastole Now the pressure in the left ventricle starts falling down The left atrium is still acting as a tank for Lung blood The mitral valve is still closed The V wave is still continuing There is now IVR or Isovolumetric relaxation. No blood is coming into the ventricle and no blood is going out of the ventricle. During this phase This is ISOVOLUMETRIC RELAXATION PHASE Onset of systole is ISOVLOUMETRIC CONTRACTION Onset of Diastole is ISOVOLUMETRIC RELAXATION: Pressure is rapidly falling so that the ventricular pressure is less than the atrial pressure.

Next Phase Fig 13 Pressure in the left ventricle really becomes less than the pressure in the left Atrium Still, the innocent atrium is working as a tank, taking in blood from the lungs Next Phase: The aortic valve is now closed, and the ventricle and aorta are now disconnected. The aorta is still working, though. It is still squeezing blood into the arterial tree. Meanwhile, the ventricle is relaxing And while the ventricle is relaxing, the pressure in the ventricle has become less than that of the atrium But still the ventricle has blood left over after the last ejection. This blood left over is called End Systolic Volume. As soon as the pressure in the ventricle becomes less than pressure in the atrium, what really happens, the mitral valve will OPEN. As soon as the mitral valve opens, now the atrium and ventricle are connected. Now all the blood in the atrium is going into the left ventricle and the V wave is dropping. This blood into the ventricle is called RAPID VENTRICICULR FILLING, but this is occurring without atrial contraction. This is PASSIVE filling Rapid Passive Ventricular Filling Phase (RPVF) (Ventricular diastole)

NOW THE NEXT PHASE. Fig 14 Ventricular diastole will continue The aortic valve is closed Ventricle is disconnected from the aorta The mitral valve is open In the ventricle: The blood left over from the last contraction is end systolic volume And rapid passive ventricular filling blood After blood accumulated blood has fallen into the ventricle The next phase: Now lungs supplying the atrium with oxygenated blood The mitral valve is open. The blood from the lungs will not be stored in the atrium The blood from the lungs goes into the ventricle It means the atrium is not working as a tank. Now atrium is just working as a conduit or a pipe between the venous return of oxygen rich blood from the lungs to the left ventricle This is Passive Slow filling because there is no atrial contraction Slow Passive Ventricular filling Phase: Diastasis Slow Passive ventricular filling phase is the longest Diastole phase Diastasis Phase

SA NODE FIRES: NEXT STAGE: ATRIAL CONTRACTS: BACK TO PHASE ONE Fig 2 ATRIAL CONTRACTS: ACTIVE VENTRICULAR FILLING PHASE: END OF CYCLE

When your heart rate is around 72 per minute: Atrial systole is only When your heart rate is around 72 per minute: Atrial systole is only .1 sec During atrial diastole, the atrium works as a simple tank Ventricular systole: is about .3 sec. ventricular diastole is about .5 seconds If your heart beats about 72 beats per minute, then ventricular diastole and systole is about .8 seconds

Summary of the cardiac cycle How many stages of cardiac cycle have we discussed? Atrial contraction: Atrial systole Atrial Diastole with the onset of ventricular contraction Venous blood accumulating via atrial diastole Ventricular systole but sill atrial diastole Ventricular diastole started but stull atrial diastole Still atrial diastole Also atrial diastole Atrial diastole is very long

Sounds of the cardiac cycle

Displaying the Cardiac Cycle via the Wiggers Diagram

What is a Wiggers Diagram Representing? The horizontal line represents the time scale The vertical line is showing the pressure changes The cardiac cycle = three parameters that need to be checked straight away: The relationship of the pressure changes in the atrium, pressure changes in the ventricle, and pressure changes in the aorta

Now we will incorporate the concept of heart sounds within the cardiac cycle The most important event is the left ventricle contraction The onset of left ventricular contraction will cause the closure of the mitral valve If you keep in mind the right side of the heart, the right ventricle will close the tricuspid valve when it contracts the same time that the left ventricle contracts. The closure of the mital and tricuspid valves at the onset of ventricular systole produces the sound which is called FIRST HEART SOUND.

First heart sound is produced with the onset of ventricular systole Closure of the mitral valve and tricuspid valve Then: during the next phase, the ventricle contracts there is increased pressure in the left ventricle, and more pressure than the aorta, then the aortic valve will open And opening of the of the aortic valve will produce NO sound Healthy valves, when they open, do not produce any sound. The next ejections phases will produce no sound also. Then: left ventricular diastole starts The ventricular pressure rapidly drops. The aorta will close the aortic valve. One the left side of the heart, the aortic valve closes, And on the right side of the heart the pulmonary valve closes So, the closure of the aortic valve and the pulmonic valve produces a sound called the second heart sound.

So S1 is produced by closure of mitral and tricuspid valves in the beginning of ventricular systole And S2 is produced by the closure of the aortic and pulmonic valves at the end of ventricular systole and at the beginning of ventricular diastole Between S1 and S2 there is ventricular systole Sometimes when there is rapid ventricular filling at the beginning of ventricular diastole, the heart makes a humble sound called S3 Then if an atrium is pumping against the hypertrophic ventricle, the atrium contraction can produce a sound: If an atrium is pumping against a stiffened ventricle, Hypertrophic ventricle, then the atri has to work harder to pump the blood into that ventricle. Strong pumping of the atri can produce a sound: S 4 which is a pathological sound. All of the above phases that are shown on the left heart, occur in the right heart. Except: the pressure within the right side of the heart is less than the pressure within the left side of the heart.

For example: Outflow tracts pressure: The pressure in the pulmonary artery varies between 8 and 25 mmHg Pressure in the aorta varies between 80 and 120 mmHg Left ventricular pressure varies from 0-120 Right ventricular pressure varies from 0-25 The cardiac events on the right side of the heart is similar than that of the left side of the heart: the only difference are the pressures. NOW: The heart sounds with the phases of the cardiac cycle. There are murmurs when the valves do not function properly, but that is not what we are reviewing now.

S3 is the sound caused by rapid ventricular filling S4 is pathologic (hypertrophic ventricle – forced contraction of the right atrium: stiffened ventricle

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