The cardiac Cycle and cardiac output.pptx

The presentation explains the normal cardiac function and normal cardiac cycle.

1. Cardiac Cycle and Cardiac Output ’

2. Contents  Cardiac Cycle  Duration Of Cardiac Cycle  Events & phases of Cardiac Cycle  Cardiac Output (CO)  Cardiac Output Measurement  Relationship of CO with BP  Summary

3. Cardiac Cycle  Refers to a complete heartbeat from its generation to the beginning of the next beat.  Cardiac events that occur from – beginning of one heart beat to the beginning of the next are called the cardiac cycle.

4. Cardiac Cycle  Initiated by spontaneous generation of AP in SA node.  Cardiac cycle has :  A period of relaxation - Diastole - during which heart fills with blood.  A period of contraction - Systole - during which blood is ejected.

5. Cardiac Cycle  Systolic Duration=0.3 sec Diastolic duration=0.5sec  During atrial systole , the ventricles are relaxed.  During ventricular systole , the atria are relaxed.  Calculation For 72 beats time is 60 sec For 1 beat=60/72=0.8 sec T otal duration of each cardiac cycle=0.8sec

6. Cardiac Cycle  Systole (0.3 s) includes: Isovolumetric contraction. Ejection.  Diastole (0.5 s) includes: Isovolumetric relaxation. Rapid ventricular filling. Slow ventricular filling (diastasis). Atrial contraction.

7. Cardiac Cycle Systole (0.3 s) Isovolumetric contraction Ejection Reduced Ejection Rapid Ejection Diastole Isovolumic relaxation Rapid ventricular filling Slow ventricular filling (diastasis). Atrial contraction

8. EVENTS IN CARDIAC CYCLE  'Lub-dub,' 'lub-dub' - This is the familiar sound of the heartbeat.  The events in cardiac cycle includes –  Systole- term used to describe the contraction of the heart.  Diastole -term used to describe the relaxation of the heart.

9. Atrial Systole Blood normally flows continually from great veins into atria : 75% flows directly from atria into ventricle BEFORE the atria contracts. 25% of filling of ventricles – atrial contraction.

10. Atrial Systole (The end of diastole) Atrial contraction is complete before the ventricle begins to contract. Atrial pressure drops when the atria stop contracting.

11. Beginning of Ven tricular Systole Isovolumetric Contraction  Atrioventricular (AV) valves close at the beginning.  Mechanically, it’s the interval between the closing of the AV valves and the opening of the semilunar valves (aortic and pulmonary valves).  Electrically, it is the interval between the QRS complex and the end of the T wave (the Q-T interval).

12. Ven tricular Systole The AV valves close when the pressure in the ventricles exceeds the pressure in the atria . As the ventricles contract isovolumetrically- their volume doesn’t change the pressure inside increases, approaching the pressure in the aorta and pulmonary arteries.

13. Ven t . Systole Ejection  The Semilunar valves ( aortic , pulmonary ) open at the beginning of this phase.  at first 2/3 rapid ejection (70%) & remaining 1/3 slow ejection (30%)  ventricles continue to contract - pressure in ventricles exceed that of in aorta & pulmonary arteries &  semilunar valves open - blood is pumped out of ventricles & volume decreases rapidly.

14. Then, pressure in the ventricles falls below the pressure in the arteries. blood in the arteries begins to flow back toward the ventricles. At the end of ejection, the semilunar valves close . Ejection

15. Diastole e, Isovolumetric relaxation  Relaxation of the heart.  Is in this state of relaxation(diastole)- the pressure within the heart is low.  The atrium in diastole has been filling with blood on top of the closed AV valv causing atrial pressure to rise grad .

16. Diastole Rapid Inflow ( Rapid Ven tricular Filling) Pressure & volume of ventricle are low in this phase and This phase lasts for 0.06 sec. AV valves are open - blood accumulated in atria flows into the ventricle . Ventricular volume increases rapidly - blood flows from the atria into the ventricles.

17. Diastole Diastasis Pressure in atria and ventricles rises slowly as blood continues to return to the heart. This decreases the rate of blood flow from atria to ventricles causes slow filling of ventricles called diastasis .

18. Diastole Diastasis Also called reduced filling phase. During rapid filling and diastasis phase about 75% of blood passes from atria to ventricles. Then next cycles begins with atrial contraction. Then Atrial Diastole begins – where the atria are relaxed after the contraction ( period of atrial relaxation for rest of cardiac cycle) having duration of 0.7 sec.

19. Figure: Events of the Cardiac Cycle

20. Cardiac Cycle Cardiac cycle https://www.youtube.com/watch?v=IS9TD9fHFv0 Cardiac output https://www.youtube.com/watch?v=vFRkSB46bl8

21. Cardiac Output  Cardiac output (Q or CO ) is the volume of blood being pumped by the heart, in particular by a left or right ventricle in the time interval of one minute.  The amount of blood the heart pumps through the circulatory system in a minute.  A normal adult has a cardiac output of about 4.7 liters of blood per minute.

22. Cardiac Output  The stroke volume output and the heart rate determine the cardiac output.  Doctors think about cardiac output in terms of the following equation: Cardiac output = stroke volume × heart rate (ml/min) (ml/beat) (beats/min)  Where, stroke volume = the amount of blood put out by the left ventricle of the heart in one contraction heart rate = number of times your heart beats per minute .

23. Cardiac Output  The cardiac output is usually expressed in liters/minute.  Someone weighing about 70 kg (154 lbs), the cardiac output at rest is about 5 liters/minute.  In a resting male, CO = 70mL/beat x 75 beats/min = 5.25L/min .  A number of clinical methods available for measurement of CO - having unique strengths and weaknesses & relative comparison.  Is limited by the absence of a widely accepted "gold standard" measurement.

24. Cardiac Output Relationship with BP As Cardiac output is made up of heart rate and stroke volume - at rest these are relatively constant.  With exercise the heart beats faster - more blood is pumped out with each beat contributing to a rise in BP .  Changes in the volume of blood within the cardiovascular system will also affect B P .

25. Cardiac Output Relationship with BP A person was severely dehydrated or lost a large quantity of blood through a wound there would be less blood for the heart to pump, thereby reducing cardiac output and BP .  For a typical, fit young person, the cardiac output might go up to about 20 liters/min at the peak of exercise .  for a world- class athlete in an endurance sport, the maximum cardiac output might be around 35 liters/min .

26. Summary Cardiac Cycle : all events associated with one heartbeat , including diastole (relaxation phase) and systole (contraction phase) of both the atria and the ventricles. During a cardiac cycle - Each heart chamber goes through systole and diastole. Correct pressure relationships are dependent on careful timing of contractions.

27. Summary The sequence of events in one cardiac cycle is –  1st is atrial systole,  Followed by atrial diastole and ventricular systole,  Finally, ventricular diastole.

28. Summary  Atrial systole (duration 0.1 sec) : Contraction of atria , increases pressure inside atria to 4- 6 mmHg in right atrium and abt. 7- 8mmHg in left atrium.  Then there is a period of atrial relaxation for rest of cardiac cycle about duration 0.7 sec.  Ventricular contraction (0.3 sec):Rising ventricular pressure exceeds the atrial pressure causing closure of AV valves(tricuspid & mitral valves) - responsible for generating 1st heart sound .  Ventricular relaxation (0.5 sec) : called heart’s state of relaxation , the pressure within the heart is low . blood passively flows through the atria and into the ventricles.

29. Summary Video https://www.youtube.com/watch?v=vFRkSB46bl8

30. Cardiac output:  The cardiac output is simply the amount of blood pumped by the heart per minute.  Necessarily, the cardiac output is the product of the heart rate , which is the number of beats per minute, and the stroke volume , which is amount pumped per beat. Summary

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