SUDIPTA BHOWMICK

7/31/2019 SUDIPTA BHOWMICK

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THE CARDIACCYCLE

BY:- SUDIPTA BHOWMICKBPT FINAL YR.



DEFINITION

It is defined as the sequence of co-ordinatedevents which take place during heart beat.

Each heart beat consist of 2 major periods:SystoleDiastole

During systole there is contraction of cardiacmuscle.

During diastole there is relaxation of cardiacmuscle.



DIVISION OF CARDIACCYCLE

Contraction of atria = Atrial systoleRelaxation of atria = Atrial diastole

Contraction of ventricles = Ventricular systoleRelaxation of ventricals = Ventricular diastole

In clinical practice systole means ventricular systole & diastole means ventricular diastole.



Continue….

So cardiac cycle is divided in two phases:--systole

-diastole



SUB DIVISION & DURATIONOF CARDIAC CYCLE

When the heart beats at the normal rate of 72/minthe duration of each cardiac cycle is about 0.8sec.

Duration of systole = 0.27sec

Duration of diastole = 0.53sec



CONTINUE…..

SYSTOLE

Isometric contraction = 0.05secEjection period = 0.22sec

DIASTOLE

Protodiastole = 0.04sec

Isovolumetric relaxation = 0.08secRapid filling phase = 0.11secSlow filling phase = 0.19sec

Atrial systole = 0.11sec



ATRIAL SYSTOLE

The end of diastole



ATRIAL SYSTOLE - HeartIt occurs during last phase of venticular diastole.Also called as second or last rapidfilling phase or presystole.Lasts for 0.11sec,

Prior to atrial systole, blood has beenflowing passively from the atriuminto the ventricle through the openAV valve.During atrial systole the atrium

contracts and tops off the volume inthe ventricle with only a smallamount of blood. Atrial contractionis complete before the ventriclebegins to contract.



ATRIAL SYSTOLEPressures & Volumes

The "a" wave occurs whenthe atrium contracts,increasing atrial pressure

slightly about5mmHg(yellow).Atrial pressure dropswhen the atria stopcontracting.



ATRIAL SYSTOLEECG

An impulse arising from the SA node results in depolarizationand contraction of the atria (the right atrium contracts slightlybefore the left atrium).

The P wave is due to this atrial depolarization.The PR segment is electrically quiet as the depolarizationproceeds to the AV node.This brief pause before contraction allows the ventricles to fill

completely with blood.



ATRIAL SYSTOLEHeart Sounds

A fourth heart sound (S4) abnormal and is associatedwith the end of atrial emptying after atrial contraction.

It occurs with hypertrophic congestive heart failure,massive pulmonary embolism, tricuspidincompetence, or cor pulmonale.



ISOVOLUMETRICCONTRACTION

The Beginning of systole



ISOVOLUMETRIC CONTRACTIONHeart

Last for 0.05secIn the beginning of venticularcontraction semilunar valves areclosed but the AV valves are notfirmly closed.As the contraction starts he IVpressure rises & AV valves closesfirmly.Ventricles contract as a closedchamber.As the presssure rises steeply AVvalve bulges inside the atriaMechanically it is a phase betweenclosing of AV valve & opening of semilunar valve..



ISOVOLUMETRIC CONTRACTIONPressures & Volumes

The AV valves close when thepressure in the ventricles (red)exceeds the pressure in the atria(yellow).As the ventricles contractisovolumetrically -- their volumedoes not change (white) -- thepressure inside increases,approaching the pressure in the aortaand pulmonary arteries (green).The ‘c’wave in atrial pressurecurve(yellow)is seen at this time & isdue to the buldging of AV valveswith in the atrum which causes slightincrease in atrial pressure.



ISOVOLUMETRIC CONTRACTIONECG

Ventricular complex of ECG begins slightly before thisphase,so later half of R WAVE is in this phase.

The QRS complex is due to ventricular depolarization, and itmarks the beginning of ventricular systole. It is so large that itmasks the underlying atrial repolarization signal. the ventriclesto fill completely with blood .



ISOVOLUMETRIC CONTRACTIONHeart Sounds

The first heart sound (S1, "lub") is due to the closingAV valves and associated blood turbulence.



RAPID EJECTION



RAPID EJECTIONHeart

As soon as the IV pressureexceeds hydrostatic

pressue of aorta,thesemilunar (aortic andpulmonary) valves openand due to contraction of ventricles, blood is ejectedout rapidly from bothventricles.Lasts for 0.13sec.



RAPID EJECTIONPressures & Volumes

Volume in the ventriclesdecreases rapidly (white).Aortic pressure rises

steeply but it remainslower than that of ventricles.As more blood enters the

arteries the presssure therebuilds until the flow of blood reaches the peak.



RAPID EJECTIONECG

ST segment occurs in this phase



RAPID EJECTIONHeart Sounds

None



REDUCED EJECTION

The end of systole



REDUCED EJECTIONHeart

It is end of systole.Lats for about 0.15sec.

During this rate of ventricular ejection falls,total blood ejected is lessthan that in rapid ejection

phase.



REDUCED EJECTIONPressures & Volumes

After the peak in ventricular andarterial pressures (red and green),blood flow out of the ventriclesdecreases and ventricular volumedecreases more slowly (white).The rate of run off exceeds the rateof inflow into the aorta, so aorticblood pressue falls.mean while ventricular pressure alsofalls & a time comes when IVpressure falls below the aorticpressure. This marks the end of ejection phase.



REDUCED EJECTIONECG

The T wave is due to ventricular repolarization.The end of the T wave marks the end of ventricular systole electrically .



REDUCED EJECTIONHeart Sounds

None



PROTODIASTOLE

It is the first stage of ventricular diastole.Lasts for 0.04secDue to ejection of blood, the pressure in pressure in aorta

& pulmonary artery increases & pressure in ventriclesdrop.When the IV pressure decreases than aortic & pulmonarypressure the semilunar valves closes.

AV valves are already closed so no other changes occur inheart during this phase.



ISOVOLUMETRICRELAXATION



ISOVOLUMETRIC RELAXATIONHeart

Starts with the closure of semilunar valve.Lasts for 0.08sec

AV valves are still closed.Therefore the ventricles act asclosed cavity & at the sametime ventricles start relaxing.

Hence here is no change inlength & volume of musclefibres.



ISOVOLUMETRIC RELAXATIONPressures & Volumes

Throughout this phase the atrium indiastole has been filling with bloodon top of the closed AV valve,causing atrial pressure to risegradually (yellow).The "v" wave is due to the back flowof blood after it hits the closed AVvalve.The pressure in the ventricles (red)continues to drop and may reach0mmHg.Ventricular volume (white) is at aminimum and is ready to be filledagain with blood.



ISOVOLUMETRIC RELAXATIONECG

No Deflections



ISOVOLUMETRIC RELAXATIONHeart Sounds

The second heart sound (S2, "dup") occurs when thesemilunar (aortic and pulmonary) valves close. S2 isnormally split because the aortic valve closes slightlyearlier than the pulmonary valve.



RAPID VENTRICULAR

FILLING



RAPID VENTRICULAR FILLINGHeart

Once the AV valves open,blood flows from the atrium toventricles with a gush.

About 70% filling of theventricles occurs during thisphase.Lasts for about 0.19sec



RAPID VENTRICULAR FILLINGPressures & Volumes

Ventricular volume (white)increases rapidly as bloodflows from the atria into the

ventricles.The atrial pressure fallsslightly but still remains morethan that of ventricles.



RAPID VENTRICULAR FILLINGECG

No Deflections



RAPID VENTRICULAR FILLINGHeart Sounds

A third heart sound (S3) is usually abnormal and is due torapid passive ventricular filling. It occurs in dilatedcongestive heart failure, severe hypertension, myocardialinfarction, or mitral incompetence.



REDUCED VENTRICULARFILLING

(Diastasis)



REDUCED VENTRICULAR FILLINGHeart

After the sudden rush of blood, the ventricles fillingslows.

About 20% of the fillingoccur s during this phase.It lasts for 0.19sec



REDUCED VENTRICULAR FILLINGPressures & Volumes

Ventricular volume (white)increases more slowly now.The ventricles continue to fill

with blood until they arenearly full.



REDUCED VENTRICULAR FILLINGECG

No Deflections is seen but it usually corresponds the phasebetween the end of T wave & next P wave.



REDUCED VENTRICULAR FILLINGHeart Sounds

None



THANK YOU

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