A Seminar on ECG (2)

8/8/2019 A Seminar on ECG (2)

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BY:NEETHI Y H

SUPRIYA K M


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ECG: ELECTROCARDIOGRAPH

It is the word derived from the Greek words: Electro: Related to Electricity Cardio: Heart

Graphy: To Write

DEFINITION:ECG is a Recording of the small electric wavesbeing generated during the Heart activity.


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HISTORY:ECG was first developed byDutchscientist

Willem Einthoven in 20th century for whichhewon the Nobelprize in Medicine.


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HOWDOESELECTRICITYCOME

FROM HEART: In the heart there are cellsspecialized in

producing electricity. These are calledpacemaker cells. Theyproduce electricity by

quickly changing their electrical charge frompositive to negative and back.

The first electric wave in aheart beat is

initiatedat the top of the heart. Because of theheart muscle cell'sability to "spread" itselectric charge to adjacentheart muscle cells,this initial wave will be enough to startachain reaction.


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PURPOSESOFECG:

To detect Heartproblems or blockages in theArteries.

To draw a graph impulses moving through

the Heart. To record Heart rate and Regularities of

Heart beat.

To diagnose apossible Heart Attackandother HeartDisorders


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HOWECGWORKS:

The ECG works by detectingandamplifying thetiny electrical changes on the skin thatarecaused when the heart muscle "depolarises"

during eachheart beat. At rest, eachheart musclecell hasa charge across its outer wall. Reducingthis charge towards zero is called de-polarisation, whichactivates the mechanisms inthe cell that cause it to contract.


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ECGMACHINE:Rather than using today'sself-adhesive

electrodes Einthoven'ssubjects would immerseeach of their limbs into containers ofsaltsolutions from which the ECG was recorded.


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ECGLEADCONFIGURATION:Einthoven assigned the letters P, Q, R, S and T tothe various deflections,and described theelectrocardiographic features ofa number ofcardiovascular disorders.


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Behold: Einthoven's Triangle!Each of the 6 frontalplaneleadshasa negative and

positive orientation (asindicated by the '+' and '-'signs). It is important torecognize that Lead I (and to alesser extent LeadsaVR andaVL)are right left in

orientation. Also, LeadaVF(and to a lesser extent Leads IIand III)are superior inferiorin orientation.

The electrodesare typically 12 in number.These are classified into:Three Standard Arm Electrodes.Three Augmented Electrodes.Six Chest Electrodes.


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Three Standard Arm LeadsAugmented Three Unipolar Leads


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PRECORDIALLEADS:


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YOCARDIAL ISCHEMIA AN

INFARCTION: Ifa coronaryartery is occluded, the transportof oxygen to the cardiac muscle is decreased,causingan oxygen debt in the muscle, which iscalled ischemia.

Ischemia causes changes in the restingpotentialand in the repolarization of the muscle cells,

which isseen as changes in the T-wave. If theoxygen transport is terminated in a certain area,the heart muscle dies in that region. This is calledan infarction.


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An infarctarea is electrically silentsince ithas

lost its excitability. The loss of this outwarddipole is equivalent to an electrical forcepointing inward. Wit h this principle it ispossible to locate the infarction.


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ADVANTAGES:

It is Painless.

It is Non Invasive.

It is Safe, Inexpensive, Easy toperform.

Large availability.

Highly compactible.


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DISADVANTAGES:

Low Sensitive.

The ECG reveals the heart rate and rhythmonly during the time that the ECG is taken. Ifintermittent cardiac rhythm abnormalitiesarepresent, the ECG is likely to miss them.

It doesntalwayspermitan accurate diagnosis.

Some Negative results.

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A Seminar on ECG (2)