PPT CARDIAC CYCLE BY DR QAZI IMTIAZ RASOOL

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DR QAZI IMTIAZ RASOOL EX. H.O.D, DEPARTMENT OF PHYSIOLOGY GOVT; MEDICAL COLLEGE SRINAGAR KASHMIR INDIA

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CARDIAC CYCLE:

CARDIAC CYCLE DR QAZI IMTIAZ RASOOL

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Objectives: By the end of this lecture, you should : Describe events in cardiac cycle. Describe atrial pressure changes during cardiac cycle. Describe ECG changes during cardiac cycle. Describe heart sounds during cardiac cycle. Identify Clinical Correlations.

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THE CARDIAC CYCLE Definition: It is the cardiac events that occur from the beginning of one heart beat to the beginning of the next beat. These events consists of periods of contraction called "systole" and a period of relaxation called "diastole" . Duration: Assuming a heart rate of 75 beat/min. the average duration of each cycle is 0.8 (60 / 75) second. When heart rate increases, the duration of each cardiac cycle decreases, including contraction and more of relaxation phases

EVENTS IN CARDIAC CYCLE :

EVENTS IN CARDIAC CYCLE 1 ELECTRIC CHANGES 2 MECHANICAL CHANGES 3 PRESSURE CHANGES 4 VOLUME CHANGES 5 PHONOCARDIOGRAPHIC CHANGES 6 VASCULAR CHANGES

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I- Atrial systole. (during which the ventricle is relaxed) II- Ventricular systole, (during which the atrium is relaxed) It occurs in 3 phases : a- Isometric (or isovolumetric ) contraction phase . b- Maximum ejection phase . c- Reduced ejection phase . III- Ventricular diastole, (during which the atrium is relaxed) (i.e., relaxation of the whole heart). It occurs in 4 phases 1.Protodiastolic phase 2. Isometric (or isovolumetric ) relaxation phase 3. Rapid filling phase. 4. Reduced filling phase. Phases of the cardiac cycle:

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Each cycle is initiated by spontaneous generation of an action potential in the sinus node . AP from SAN travels rapidly through both atria and then through the A-V bundle into the ventricles. Delay in A- Vnode of 0.1 second during passage of the cardiac impulse from the atria into the ventricles. This allows the atria to contract before ventricular contraction, thereby pumping blood into the ventricles before the strong ventricular contraction begins.

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N ARROWING ORIFICES;- i.e , S,V,C,.I,V,C, pulmonary Inertia of the blood keeps itv moving some regurgitation of blood into the veins. DURATION ;- 0.1 sec VALVES;- A-V valve open, Semilunar closed VENTRICULAR VOLUME;- i ncreases INTRAVENTRICULAR PRESSURE ↑ slightly due to rush of blood from the atria, then decreases again as the ventricles are still relaxed (it dilate) E.C.G; - P wave starts 0.02 second before atrial systole SOUNDS ;- 4 th I- Atrial Systole ( primer pumps for ventricles)

Clinical application:

Clinical application Heart operate under most conditions even without this extra 20 % effectiveness because it normally can pump 300 to 400 % more blood than is required by the resting body. Atria failing is unlikely to be noticed unless a person exercises; then acute signs of heart failure occasionally develop, especially shortness of breath.

II- VENTRICULAR SYSTOLE 1. - Isometric (or isovolumetric) contraction phase. :

II- VENTRICULAR SYSTOLE 1. - Isometric (or isovolumetric ) contraction phase . Immediately after ventricular contraction, pressure rises abruptly, causing the A-V valves to close. additional 0.02 to 0.03 sec. is required for sufficient pressure to open semilunar valves against the pressures in the aorta and pulmonary artery. contraction in the ventricles, but there is no emptying. as a closed chamber ( period of isovolumic or isometric contraction, ) DURATION ;- 0.05 sec VALVES;- A-V valve closed, Semilunar closed INTRAVENTRICULAR PRESSURE rapidly (close AV VALVES) 0 80mm

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II- VENTRICULAR SYSTOLE 2. 2 PERIOD OF EJECTION left ventricular pressure above 80 mm Hg (right 8 ) push the semilunar valves open., 70 % in1st 1/3 rd as period of rapid ejection for 0.15 sec 30 % 2 nd 2/3 rd . period of slow ejection. For 0.1 sec. VALVES;- A-V valve closed ,Semilunar open VENTRICULAR VOLUME;- deceases INTRAVENTRICULAR PRESSURE pressure is slightly higher than the aortic pressu

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PROTO means FIRST 0.04 sec. Period of start of relaxation It ends when momentum of the ejected blood is overcome and the aortic and pulmonary valves close , setting up transient vibrations in the blood and blood vessel walls III- Ventricular diastole , (i.e., relaxation of the whole heart ) 1. Protodiastolic phase

II- VENTRICULAR DIASTOLE 2. Isometric (or isovolumetric) Relaxation phase:

II- VENTRICULAR DIASTO LE 2. Isometric (or isovolumetric ) Relaxation phase Ventricular muscle continues to relax, The ventricle is now a completely closed chamber even though the ventricular volume does not change, giving rise to the period of isovolumic or isometric relaxation . DURATION ;- 0.03-0.06 sec VALVES;- A-V valve closed, Semilunar closed INTRAVENTRICULAR PRESSURE rapidly decreases

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pressures decrease rapidly back to their low diastolic levels . A-V valves open. 70 % ventricular filling sudden rush of blood from the atrium to ventricle causes= 3rd heart sound pressure gradient facilitates passive process . Duration 0.09 sec E.C.G U wave may be present SOUND 3 rd INTRAVENTRICULAR PRESSURE rapidly increases II- VENTRICULAR DIASTO LE 3 . Initial Rapid Filling Phase :

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II- VENTRICULAR DIASTO LE 4 . Diastasis (slow Filling Phase ) 0.19 second middle third of diastole 5% P ressure falls in the atrium , intraventricular pressure. 4. pressure gradient decreases. – stop FAST HEART RATE -diastasis is affected .

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Systolic B.P. in the left ventricle = 130 mmHg Diastolic B.P in the left ventricle = zero Systolic B. P. in the right ventricle = 35 mm Hg Diastolic B. P. in the right ventricle = zero Systolic B. P. in the aorta = 120 mm Hg Diastolic B. P. in the aorta = 80 mm Hg Systolic B. P. in pulmonary artery = 30 mm Hg Diastolic B. P. in pulmonary artery = 10 mm Hg . end-diastolic volume . EDV 110 to 120 ml stroke volume SV 70 ml end-systolic volume . ESV 50 ml

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