heart.pptx

7/28/2019 HEART.pptx

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CARDIOVASCULAR SYSTEM


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MYOCARDIAL INFRACTION

Coronary heart disease is the greatest single cause fordeath in most cases in the Universe.

The most frequent cause is the myocardial infarction.

Therefore, it is important to understand the

cardiovascular system thoroughly, so as to takesubsequent prevention against the heart disease.

The metabolism process of the cell needs nutrientsand excretes waste products; the circulatory system

provides these nutrients and removes thesewasteproducts.


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Function of the HEART

HEART is the major component of Circulatorysystem.

Heart supplies the power required to circulate theblood throughout the body.

Hearttwo pumps in series.

RHS provides the power required to force bloodthrough the lungs.

LHS provides the power required to force bloodthroughout bodyvia capillaries.


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Simplified block diagram of the circulatory

system


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HEART


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Cell revitalization

The aorta curves in an arch up from the heart, downalong the back bone and into the abdomen; from itother large arteries lead to the head, the digestiveorgans, the arms and the legs.

From these arteries branch the smaller arterioles andfrom these, branch billions of tinycapillaries.

By the time blood has reached the capillaries, it ismoving slowly along channels.

These channels are only about 10 microns in diameter.

Here the blood discharges its load ofdissolved foodand oxygen to the body cells.


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Functional model of the cardiovascular

system


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These cells in turn deposit waste materials such as

carbon-di-oxide into the blood stream. In yieldingoxygen and taking on the waste, the blood turns colourform bright red to dull red or blue.

The blood now starts back to the heart passing fromthe capillaries into thevenules.

The venules converge into larger veins and then intothe two largest veins just above and below the heart,known as venacava.


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HEART


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The blood empties into right atrium.

It is pumped into the right ventricle and then movesout through the pulmonary artery to the lungs.

The lungs then supply the blood with fresh oxygen.

The blood passes form the lungs to the left atrium,

then is pumped into the left ventricle and passes viathe aorta.

This is done for repeating the circulation process.


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This general flow throughout the body is known as thesystemic circulation; the flow to and from thelungs is known as the pulmonary circulation.

The waste products contained in the blood areremoved by the kidneys and liver.

The average quantity of blood in a mans body is aboutfive liters.

This is completely circulated through the body inapproximatelyone minute.

5 L/min


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THE HEART: Anatomy

The heart is a hollow, cone-shaped, muscular pump locatedwithin the mediastinum of the thorax & resting upon thediaphragm.

The heart itself weighs less than half a kilogram, is almost about 15cm long at its maximum dimension.

The heart lies pointed downward to the chest cavity to the left ofthe mid-center body line.

The heart has a covering as well as lining.

Its covering, the pericardium, consists of three layers of fibroustissues with a small space in between, filled with a thin film ofpericardial fluid.


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Septum


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THE HEART

The left and right sides of the heart are separated bythe septum, or dividing wall of tissue.

The entire walls of the heart are made of muscle;within these walls are four hollow chambers, a left andright receiving chamber (atrium) and below them a

left and right pumping chamber (ventricle).


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The Heart Valves

Thetricuspid valve regulates blood flowbetween the right atrium and right

ventricle.

Thepulmonary valve controls bloodflow from the right ventricle into the

pulmonary arteries.

The mitral valve lets oxygen-rich bloodfrom your lungs pass from the leftatrium into the left ventricle.

The aortic valve lets oxygen-rich bloodpass from the left ventricle into theaorta, then to the body.


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Cardiac cycle or the Mechanical activity

It is characterized by the following events.

With a person in a sitting position, the heart beats (orcontracts) about 70 times per minute.

With each beat, a quantity of blood is driven throughthe heart.


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Cardiac cycle or the Mechanical activity

The onset ofsystole is initiated by contraction of themuscles surrounding the atria.

This propels additional blood into the ventricles.

Theventricles then begin to contract, thereby causing arise in pressure within the ventricles.

This increased pressure shutstwo atrioventricular valves(Tricuspid and Bicuspid).

With further contraction, the pressure continues to rise.


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Electrophysiology of the cardiac muscle cell


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HEART


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Systemic circulation

Once the pressure of the systemic and pulmonarycirculations are exceeded, a phase ofventricularejection is begun.

The aortic valve is forced to open.

Then the blood is squeezed into aorta and thence intothe systemic circulation.

This blood flow leading in to the aorta can be

considered as a wave, with a peak pressure about 120mmHg (called the systolic pressure) and a lowpressure about 80 mmHg (called the diastolic

pressure).


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Arterial blood pressure waveform

Dicrotic notch-represents a reflected pulse due toslight back pressure built up as the mitral valve

closes

Systolicpressure

Diastolic

pressure

Time

Pressure(mmHg)


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Pulmonary circulation

Similarly, the pulmonary valve is forced open andblood is supplied to the pulmonary circulation.

After the ventricular contents are partially ejected, themuscles surrounding the ventricles relax and theventricular pressure falls.

As soon as these pressures fall below the pressuressustained in the circulatory systems, the aortic andpulmonary valves close, signaling the onset of diastole.


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El t i l t ti l t d ith i th


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Electrical potentials generated with in the

HEART

The muscle contraction is initiated by stimulation. The right atrium consists of a bundle of nerves known

as the Sinoartrialnode (SA node).

This type of nerve system is found nowhere else in thebody.

Its function is to start the heart beat and set its rhythmor pace; this node is also called as cardiac pacemaker ornatural pacemeaker and generate impulses at a normalrate of the heart, about 70bpm at rest.


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The electrical and mechanical output from the heart is

initiated by stimulation from this nodewhich resultsin contraction of the various heart muscles.

Impulses generated by the SA Node stimulate

contraction of the muscles comprising the atria.

These impulses also travel along conducting fibers in

the atrium to the Atrioventricular node (AV Node),stimulating the depolarization of this node.


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The AV Node is located in the lower part of the heart-wall between the two atria on the septum, and acts as adelay line to provide timing between the action of theAtria and Ventricles.

Stimulation of the AV Node causes impulses to be sentto the myocardium or muscles comprising theventricles via the bundle of his, two bundle brancheson each of the septums and the fine purkinjefibers,

which arborize in the ventricular muscle.


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The Conduction System


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Thus the Atria and Ventricles are functionallylinked

only by the AV Node and the conduction system.

The AV delay is provided so that the atrial contractionis complete the ventricular filling before thecontraction of the ventricles.

So, the muscular contractions necessary to maintainthe hearts pumping action are initiated bydepolarization and repolarization of the SA Node and

then depolarization and subsequent repolarization ofthe AV Node.


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When the ventricles are depolarizing, the atria arerepolarizing.

These depolarizations and repolarizations generateexternal action potentials which can be recorded at the

surface of the body. These external potentials generated from within the

heart are known as the electrocardiogram or ECG.


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Heart Electrical Activity (ECG)

1)Depolarization of the SA node and a resultingcontraction of the muscles surrounding the atria.

This results in externalaction potential known as Pwave.

2)Immediately following this depolarization,repolarization of the atria occurs.

However, for some reason, this does not generate a pronounced actionpotential.

This potential is known as the TA wave and is rarelyobserved in practice.


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Electrical activity produced by depolarization of theSA node travels through fibers within the atrium to the

AVnode.

The time taken for this electrical stimulation to travelform the SA node to the AV node is known as theatrioventricular conduction time and is typicallybetween 120ms and 220ms.


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When this stimulation reaches theAV node, this nodedepolarizes and the depolarization is conducted down

through the bundle of His to the myocardium musclecausing ventriculardepolarization.

The external action potential is referred to as QRS

complex.

Immediately following this depolarization, the cellsconcerned repolarize.

This results in ventricular repolarization or the Twave.


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Many ECG waveforms also show an additional waveoccurring after the T wave.

This is designated the U wave (after potentials) andits origin is unknown.


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Electrophysiology of the heartDifferent waveforms for each of the specialized cells


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ECG WAVEFORM


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ECG parameters: Amplitude

P-wave 0.25 mv

R-wave 1.60 mv

Q-wave 25% R- wave

T-wave 0.1-0.5 mv


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ECG parameters: Duration

P-R interval 0.12-0.22 s

Q-T 0.35-0.44 s

S-T 0.05-0.15 s

P-wave 0.11 s

QRS 0.09-0.10 s


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Detail of the QRS complex, showingventricular activationtime (VAT) and amplitude
http://en.wikipedia.org/wiki/QRS_complexhttp://en.wikipedia.org/wiki/Ventricular_activation_timehttp://en.wikipedia.org/wiki/Ventricular_activation_timehttp://en.wikipedia.org/wiki/Ventricular_activation_timehttp://en.wikipedia.org/wiki/Ventricular_activation_timehttp://en.wikipedia.org/wiki/Ventricular_activation_timehttp://en.wikipedia.org/wiki/Ventricular_activation_timehttp://en.wikipedia.org/wiki/QRS_complex


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http://en.wikipedia.org/wiki/File:ECG_priciple_slow.gif

Feature Description Duration


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RR intervalThe interval between an R wave and the nextR wave: Normal resting heart rate is between60 and 100 bpm.

0.6 to 1.2s

P wave

During normal atrial depolarization, the mainelectrical vector is directed from the SA node

towards the AV node, and spreads from therightatrium to the left atrium. This turns intothe P wave on the ECG.

80ms

PR interval

The PR interval is measured from thebeginning of the P wave to the beginning ofthe QRS complex. The PR interval reflects the

time the electrical impulse takes to travel fromthe sinus node through the AV node andentering the ventricles. The PR interval is,therefore, a good estimate of AV nodefunction.

120 to 200ms

PR segment

The PR segment connects the P wave and the

QRS complex. The impulse vector is from theAV node to the bundle of His to the bundlebranches and then to the Purkinje fibers. Thiselectrical activity does not produce acontraction directly and is merely travelingdown towards the ventricles, and this showsup flat on the ECG. The PR interval is moreclinically relevant.

50 to 120ms
http://en.wikipedia.org/wiki/RR_intervalhttp://en.wikipedia.org/wiki/R_wavehttp://en.wikipedia.org/wiki/Beats_per_minutehttp://en.wikipedia.org/wiki/P_wave_(electrocardiography)http://en.wikipedia.org/wiki/Atrium_(anatomy)http://en.wikipedia.org/wiki/Atrium_(anatomy)http://en.wikipedia.org/wiki/Atrium_(anatomy)http://en.wikipedia.org/wiki/Atrium_(anatomy)http://en.wikipedia.org/wiki/P_wave_(electrocardiography)http://en.wikipedia.org/wiki/Beats_per_minutehttp://en.wikipedia.org/wiki/R_wavehttp://en.wikipedia.org/wiki/RR_interval


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QRS complex

The QRS complex reflects the rapiddepolarization of the right and leftventricles. They have a large musclemass compared to the atria, so the

QRS complex usually has a muchlarger amplitude than the P-wave.

80 to 120ms

J-point

The point at which the QRS complexfinishes and the ST segment begins, itis used to measure the degree of STelevation or depression present.

N/A

ST segment

The ST segment connects the QRScomplex and the T wave. The STsegment represents the period whenthe ventricles are depolarized. It isisoelectric.

80 to 120ms


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T wave

The T wave represents the repolarization(or recovery) of the ventricles. Theinterval from the beginning of the QRScomplex to the apex of the T wave is

referred to as the absolute refractoryperiod. The last half of the T wave isreferred to as the relative refractoryperiod (or vulnerable period).

160ms

ST interval The ST interval is measured from the Jpoint to the end of the T wave. 320ms

QT interval

The QT interval is measured from thebeginning of the QRS complex to theend of the T wave. A prolonged QT

interval is a risk factor for ventriculartachyarrhythmias and sudden death. Itvaries with heart rate and for clinicalrelevance requires a correction for this,giving the QTc.

Up to 420ms in heart rate of 60 bpm
http://en.wikipedia.org/wiki/ST_intervalhttp://en.wikipedia.org/wiki/ST_interval


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U wave

The U wave is hypothesized tobe caused by the repolarizationof the interventricular septum.

They normally have a lowamplitude, and even more oftencompletely absent. They alwaysfollow the T wave and alsofollow the same direction inamplitude. If they are tooprominent, suspecthypokalemia, hypercalcemia or

hyperthyroidism usually.[29]

J wave

The J wave, elevated J-point or

Osborn wave appears as a latedelta wave following the QRS oras a small secondary R wave. Itisconsidered pathognomonic ofhypothermia or hypocalcemia.[30]
http://en.wikipedia.org/wiki/Electrocardiographyhttp://en.wikipedia.org/wiki/Pathognomonichttp://en.wikipedia.org/wiki/Hypothermiahttp://en.wikipedia.org/wiki/Hypothermiahttp://en.wikipedia.org/wiki/Hypocalcemiahttp://en.wikipedia.org/wiki/Electrocardiographyhttp://en.wikipedia.org/wiki/Electrocardiographyhttp://en.wikipedia.org/wiki/Hypocalcemiahttp://en.wikipedia.org/wiki/Hypothermiahttp://en.wikipedia.org/wiki/Hypothermiahttp://en.wikipedia.org/wiki/Pathognomonichttp://en.wikipedia.org/wiki/Electrocardiography


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A Wiggers diagram, showing the cardiac cycle events occuring in the left

ventricle.


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In the atrial pressure plot: wave "a" corresponds to atrial

contraction, wave "c" corresponds to an increase in pressure fromthe mitral valve bulging into the atrium after closure, and wave"v" corresponds to passive atrial filling.

In the electrocardiogram: wave "P" corresponds to atrialdepolarization, waves "QRS" correspond toventriculardepolarization, and wave "T" corresponds toventricularrepolarization.

In the phonocardiogram: The sound labeled 1st contributes tothe S1 heart sound and is the reverberation of blood from thesudden closure of the mitral valve (left A-V valve) and the soundlabeled "2nd" contributes to the S2 heart sound and is thereverberation of blood from the sudden closure of the aortic

valve.

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