EKG Basics - Short

8/8/2019 EKG Basics - Short

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EKG BasicsEKG Basics


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OutlineOutline

1.1. Review ofthe conduction systemReview ofthe conduction system

2.2. EKG waveforms and intervalsEKG waveforms and intervals

3.3. Determining heart rateDetermining heart rate4.4. Determining QRS axisDetermining QRS axis


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The Normal Conduction SystemThe Normal Conduction System


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Waveforms and IntervalsWaveforms and Intervals


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Determining the Heart RateDetermining the Heart Rate

Rule of 300Rule of 300

10 Second Rule10 Second Rule


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Rule of 300Rule of 300

Take the number of big boxes betweenTake the number of big boxes between

neighboring QRS complexes, and divide thisneighboring QRS complexes, and divide this

int

o 300.Th

e result

will

be approximat

el

yint

o 300.Th

e result

will

be approximat

el

yequalto the rateequalto the rate

Although fast, this method only works forAlthough fast, this method only works for

regular rhythms.regular rhythms.


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What is the heart rate?What is the heart rate?

(300 / 6) = 50 bpm

www.uptodate.com


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(300 / ~ 4) = ~ 75 bpm

www.uptodate.com


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(300 / 1.5) = 200 bpm


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The Rule of 300The Rule of 300

It may be easiestto memorize the following table:It may be easiestto memorize the following table:

# of big# of big

boxesboxes

RateRate

11 300300

22 150150

33 100100

44 7575

55 6060

66 5050


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10 Second Rule10 Second Rule

As most EKGs record 10 seconds of rhythm perAs most EKGs record 10 seconds of rhythm per

page, one can simply countthe number of beatspage, one can simply countthe number of beats

present on the EKG and multiply by 6 to getthepresent on the EKG and multiply by 6 to getthenumber of beats per 60 seconds.number of beats per 60 seconds.

This method works well for irregular rhythms.This method works well for irregular rhythms.


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33 x 6 = 198 bpm

The Alan E. Lindsay ECG Learning Center ; http://medstat.med.utah.edu/kw/ecg/


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The QRS AxisThe QRS Axis

The QRS axis represents the net overallThe QRS axis represents the net overall

direction ofthe hearts electrical activity.direction ofthe hearts electrical activity.

Abnormalities of axis can hint at:Abnormalities of axis can hint at:

Ventricular enlargementVentricular enlargement

Conduction blocks (i.e. hemiblocks)Conduction blocks (i.e. hemiblocks)


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The QRS AxisThe QRS Axis

By near-consensus, the

normal QRS axis is defined

as ranging from -30 to +90.

-30 to -90 is referred to as a

left axis deviation (LAD)

+90 to +180 is referred to as

a right axis deviation (RAD)


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Determining the AxisDetermining the Axis

The Quadrant ApproachThe Quadrant Approach

The Equiphasic ApproachThe Equiphasic Approach


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Predominantly

Positive

Predominantly

Negative

Equiphasic


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1. Examine the QRS complex in leads I and aVF to determine1. Examine the QRS complex in leads I and aVF to determine

ifthey are predominantly positive or predominantlyifthey are predominantly positive or predominantly

negative. The combination should place the axis into onenegative. The combination should place the axis into one

ofthe 4 quadrants below.ofthe 4 quadrants below.


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2. In the eventthat LAD is present, examine lead II to2. In the eventthat LAD is present, examine lead II todetermine ifthis deviation is pathologic. Ifthe QRS in II isdetermine ifthis deviation is pathologic. Ifthe QRS in II ispredominantly positive, the LAD is nonpredominantly positive, the LAD is non--pathologic (in otherpathologic (in otherwords, the axis is normal). If it is predominantly negative, itwords, the axis is normal). If it is predominantly negative, it

is path

ologic.is pa

thologic.


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Quadrant Approach: Example 1Quadrant Approach: Example 1

Negative in I, positive in aVF RAD

The Alan E. LindsayECG Learning Centerhttp://medstat.med.utah.edu/kw/ecg/


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Quadrant Approach: Example 2Quadrant Approach: Example 2

Positive in I, negative in aVF Predominantly positive in II

Normal Axis (non-pathologic LAD)

The Alan E. LindsayECG Learning Centerhttp://medstat.med.utah.

edu/kw/ecg/


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The Equiphasic ApproachThe Equiphasic Approach

1. Determine whichlead contains the most equiphasic QRS1. Determine whichlead contains the most equiphasic QRScomplex. The factthatthe QRS complex in this lead iscomplex. The factthatthe QRS complex in this lead isequally positive and negative indicates thatthe netequally positive and negative indicates thatthe netelectrical vector (i.e. overall QRS axis) is perpendicularelectrical vector (i.e. overall QRS axis) is perpendicular

to the axis ofthis particularlead.to the axis ofthis particularlead.

2. Examine the QRS complex in whicheverlead lies 902. Examine the QRS complex in whicheverlead lies 90away from the lead identified in step 1. Ifthe QRSaway from the lead identified in step 1. Ifthe QRScomplex in this second lead is predominantly positive,complex in this second lead is predominantly positive,than the axis ofthis lead is approximately the same asthan the axis ofthis lead is approximately the same asthe net QRS axis. Ifthe QRS complex is predominantlythe net QRS axis. Ifthe QRS complex is predominantlynegative, than the net QRS axis lies 180negative, than the net QRS axis lies 180 from the axisfrom the axisofthis lead.ofthis lead.


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Equiphasic Approach: Example 1Equiphasic Approach: Example 1

Equiphasic in aVF Predominantly positive in I QRS axis 0



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Equiphasic Approach: Example 2Equiphasic Approach: Example 2

Equiphasic in II Predominantly negative in aVL QRS axis +150


EKG Basics - Short

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