Prelab Full ECG lect for Bignners (Second Year Medical Students)

8/14/2019 Prelab Full ECG lect for Bignners (Second Year Medical Students)

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Reading ECGs

Dr Sherwan R ShalDr Sherwan R Shal20072007

ExclusiveExclusive


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YOU should have the followYOU should have the follow

Patients IDs e.g. name,Patients IDs e.g. name,

Date (in years, months, dayDate (in years, months, dayhours and minutes).hours and minutes).

Place where ECG was taken.Place where ECG was taken. ALL written or printed on thALL written or printed on th

ECG paperECG paper


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You should be able to

Differentiate normal from abnormaDifferentiate normal from abnormaAnd at this level:And at this level:

3.3. Heart rate.Heart rate.

4.4. Rhythm.Rhythm.

5.5. Time duration.Time duration.6.6. Voltage amplitude.Voltage amplitude.

7.7. Heart axis, deviations to right orHeart axis, deviations to right or

8.8. Overall wave forms and confi urOverall wave forms and configur


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ECG is recorded on a paper whidivided by horizontal and verticlines forming squares.

A large square is divide into 25 squares.

One large square is (5 X 5) squa


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Horizontal line represents time.Horizontal line represents time.

So, one small square equals to 1/25 secoSo, one small square equals to 1/25 secoequals to 0.04 second.equals to 0.04 second.

And, one large square equals to 1/5 secoAnd, one large square equals to 1/5 seco

5 large squares5 large squares

= one second= one secondOne largeOne largesquaresquare

= 0.2 second= 0.2 second

25 s25 ssqusqu

= one = one one one squsqu

= 0.04= 0.04


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Vertical line represents voltage.Vertical line represents voltage.

Traditionally, every 1o small squares (or 2 largTraditionally, every 1o small squares (or 2 largsquares) up or down is 1mV.squares) up or down is 1mV.

So, one small square is 1/10 or 0.1 mV.So, one small square is 1/10 or 0.1 mV.

Two largeTwo largeSquaresSquares

1 mV1 mV

One largeOne largesquaresquare0.5 mV0.5 mV

One small squarOne small squar0.1 mV0.1 mV


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Measurements

1.1. MeasurementsMeasurementsHeart Rate: 60 - 100 bpmHeart Rate: 60 - 100 bpmPR Interval: 0.12 - 0.20 sec (= PR Interval: 0.12 - 0.20 sec (= small sq.)small sq.)

QRS Duration: 0.06 - 0.10 sec (QRS Duration: 0.06 - 0.10 sec (to 2.5 small sq.)to 2.5 small sq.)=

Corrected QT interval = QT interva


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Measurements

2. Rhythm:2. Rhythm: Normal sinus rhytNormal sinus rhytThe P waves in leads I and II mustThe P waves in leads I and II mustupright (positive) if the rhythm iupright (positive) if the rhythm icoming from the sinus node.coming from the sinus node.

3. Conduction:3. Conduction:Normal Sino-atrial (SA), Atrio-ventricularNormal Sino-atrial (SA), Atrio-ventricular

and Intraventricular (IV) conductionand Intraventricular (IV) conductionBoth the PR interval and QRS duration shBoth the PR interval and QRS duration sh

within the limits specified above.within the limits specified above.P Wave P duration < 0.12 sec P amplituP Wave P duration < 0.12 sec P amplitu


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Normal Voltages in the

The voltage of the QRS complexThe voltage of the QRS complexusually is 1.0 to 1.5 millivolt frousually is 1.0 to 1.5 millivolt frotop of the R wave to the bottomtop of the R wave to the bottomthe S wave;the S wave;

The voltage of the P wave is betThe voltage of the P wave is bet0.1 and 0.3 millivolt;0.1 and 0.3 millivolt;

The voltage of T wave is betweeThe voltage of T wave is betwee


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P-Q or P-R Interva

The time between the beginning of thThe time between the beginning of thwave and the beginning of the QRS cowave and the beginning of the QRS cois the interval between the beginningis the interval between the beginningelectrical excitation of the atria and telectrical excitation of the atria and tbeginning of excitation of the ventricbeginning of excitation of the ventric

This period is called the P-Q interval.This period is called the P-Q interval.The normal P-Q interval is about 0.16The normal P-Q interval is about 0.16second. (Often this interval is called tsecond. (Often this interval is called tinterval because the wave is likel interval because the Q wave is likel


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Heart Rate

Heart rate is measured inbeats/minute.

ECG paper speed is in mm/secowe should change it to mm/min

25 mm/second equals to 60X25mm/second

= 1500 mm/min. (1500 small


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Heart Rate

= 1500 / No. of small sq. b= 1500 / No. of small sq. bRR wavesRR waves

= 300/ No. of large sq. bet= 300/ No. of large sq. bet


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Applications

QRQRSS

RR intervalRR interval

Time (seconds)Time (seconds)

o

llttaa


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Applications

QRQRSS

HeartHeart

rateratePPdurationdurationP VoltageP VoltageQRSQRS

durationdurationQTQT


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Regular Rhythm

RegularRegular

if theif thedistancedistancebetweenbetweentwotwosuccessisuccessi

ve Rve Rwaves Rwaves Rregularregularand alland allotherotherwavewave


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Irregular Rhythm

IrregularIrregular

if theif thedistancedistancebetweenbetweentwotwosuccessisuccessi

ve Rve Rwaves Rwaves R


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Heart AxisHeart Axis

The hexagonal referenceThe hexagonal referencesystemsystem

Remember..Remember..

I is 0 angle (or 180 degreI is 0 angle (or 180 degre II is 60 degreeII is 60 degree


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II

IIIIaVaVffIIIIII


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II

IIIIaVaVff

LLEFTEFT

IIIIII


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II

IIIIaVaVff

RIGHRIGHTT

IIIIII


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Physiological Causes of Physiological Causes of

When the diaphragm ascendWhen the diaphragm ascendwith expiration, the heartwith expiration, the heartbecomes more horizontal (i.becomes more horizontal (i.deviates to the left)deviates to the left)

Inspiration, on the other hanInspiration, on the other hanmakes the diaphragm tomakes the diaphragm to

h i l i l f


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Physiological Causes of Physiological Causes of

Diaphragm moves down witDiaphragm moves down witinspiration, standing (becauinspiration, standing (becauabdominal contents descendabdominal contents descendthis happen also with tallthis happen also with tall

persons.persons. Diaphragm moves up withDiaphragm moves up with

expiration, lying down, or inexpiration, lying down, or in


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AXIS DEVIATIONAXIS DEVIATION

Horizon

Horizon

taltal

Heart

Heart

LAD

LAD

Norm

Norm

alal

Ver

He

R

HH

earteart

DiaphraDiaphra

gmgm


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The axis of the heaThe axis of the hea

Normal cardiac axis isNormal cardiac axis is

It is close toIt is close tolead IIlead II

It might shift toIt might shift tothe left or tothe left or to

RRighightt


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Left AxisLeft Axis

Axis is to theAxis is to theleft ofleft ofhexagonalhexagonal

referencereferencesystem.system.


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Left AxisLeft Axis

Axis is to theAxis is to theleft ofleft ofhexagonalhexagonal



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Right AxisRight Axis

Axis is to theAxis is to theright ofright ofhexagonalhexagonal


i h i


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Right AxisRight Axis

Axis is to theAxis is to theright ofright ofhexagonalhexagonal


L f d Ri h i


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Left and Right axis

II

IIII

II

RARALALA


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NormalNormal

T t Y K l dT t Y K l d


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Test Your KnowledTest Your Knowled

T t Y K l dT t Y K l d


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Test Your KnowledTest Your Knowled


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Prelab Full ECG lect for Bignners (Second Year Medical Students)

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