1
Advanced EKG Reading

• Stefan Da Silva
• With special guest.
• Dr. S. Weeks

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Outline

• Quick review of EKG basic interpretation
• Dr. Weeks to take over

3
Basics

• Cant really do the advanced without the
  basics.
• Rate, Rhythm, Axis, Intervals, Infarction

4
Basics

• Rate
• SA node NORMALLY sets rate, usually cannot fire
  faster then 220 bpm.
• Ectopic beats will fire whenever they want and
  are usually considered abnormal (PVC, PAC, etc).
• Atrial ectopic pacemakers inherently fires 75
  bpm
• AV nodal pacemaker enjoys 60 bpm
• Ventricular pacemaker likes 30 40 bpm
  (idoventricular rhythm)
• HOWEVER, all the above will fire between 150
  250 bpm in pathological and emergency situations
  and ectopic pacemakers will take over the rhythm
  when they are firing faster that SA node.
• When the SA node fails and the ectopic site
  takes over that escape beat/rhythm.
• Tachycardia and Bradycardia
• 300, 150, 100 then 75, 60, 50 (measured from R
  wave to R wave)

5
Basics

• Rhythm
• Sinus vs non-sinus
• Regular vs Irregular
• Sinus
• P wave in front of every QRS with P wave positive
  in II, III, aVF and neg in aVR.
• Sinus arrhythmia
• Irregular rhythm but identical p waves
• Non-sinus
• Can be varying rhythm, extra/skipped beats,
  rapid rhythm, heart blocks.

6
Basics

• Axis
• More than just thumb up/thumb down and leads I
  and aVF
• Refers to direction of electrical
  stimulus/depolarization.
• Related to ventricular depolarization
• Mean QRS vector general direction of
  ventricular depolarization
• Usually pointed downward and slightly to left
  since the vectors representing depolarization
  of left ventricle are larger due to thicker wall
  and septum (septum usually depolarizes from left
  to right.)

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Basics
8
Basics
9
Basics

• Mean QRS vector

10
Basics

• Remember these diagrams

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Basics

• Axis
• Therefore if heart is displaced to right then
  Mean QRS vector will be displaced as well
• A hypertrophied ventricle has greater electrical
  activity therefore mean vector will be displaced
  to that side
• In infarction, dead myocardium cannot conduct
  therefore mean QRS vector tends to point away
  from infarcted area.

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Basics

• Axis
• Calculation

13
Basics

• Axis
• Examine lead I
• If positive QRS then vector located in left half
• If negative QRS then vector located in right half
• Examine lead aVF
• If positive QRS then vector points downward
• If negative QRS then vector points upward
• This will give you the general quadrant
• ie. Why the thumb rule works.

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Basic

• Axis
• Then find most isoelectric lead and mean vector
  will be at about 90 degrees towards the already
  specified quadrant
• Plot it out.it helps.
• Why is axis important.
• It can help with diagnosis
• extreme RAD ? Vtach, hyperK.
• RAD ? RVH, PE, VSD
• LAD ? inf MI, hyperK, poor LV function, dilated
  LV, LAFB, LVH.

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Basics

• Intervals/Segments
• PR interval
• Start of P wave to start of QRS
• Normal 0.12 - 0.2 sec
• Remember each small square is 0.04 sec
• QRS interval
• Start of QRS to end of QRS
• Normal lt 0.12
• QT interval
• Start of Q wave (or R wave if not Q) to
  termination of T wave.
• Quick and dirty usually prolonged if greater
  than half the R-R interval
• QTc

16
Basics

• Bundle Branch Block
• More than the bunny ears
• Leads V1 and V6 (chest leads)
• Determine which direction the last half of the
  QRS is pointing, it will point to the ventricle
  that is depolarizing last, which will be the side
  of the bundle branch block.
• Dr. Weeks to explain better than me.

17
Basics

• A little more on P waves
• Ensure going in right direction
• Tall P wave lead II ? right atrial abnormality
  (look for RAD, RVH)
• Wide P wave lead II /- negative portion V1 ?
  left atrial abnormality (look for MR, MS, AS, HCM)

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Basics

• Hypertrophy
• Increase in the thickness of the wall of that
  chamber.
• Right Ventricular Hypertrophy
• R wave of V1 gets progessively smaller
• Left Ventricular Hypertrophy
• S wave in V1 plus R wave in V5 gt 35 mm
• T wave inversion can also occur
• Also if gt 10mm in I or aVL then LVH

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Basics

• Infarction
• Ischemia, injury, infarction
• T wave inversion ? ischemia
• ST segment elevation/depression ? injury
• Elevation gt 1 mm in 2 or more contigous leads
• Depression gt 0.5 mm in 2 or more contigous leads

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Basics
I Lateral aVR V1 Septal V4 Anterior
II Inferior aVL Lateral V2 Septal V5 Lateral
III Inferior aVF Inferior V3 Anterior V6 Lateral
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Basics

• Lots to remember and lots of variation but
  remember the basics and then work from there.