Introduction to EKG

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Introduction to EKG

• And then a little more

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• To get an accurate EKG, leads must be properly
  applied

aVR RA(-) to LA LL() aVL LA() to RA
LL() aVF LL() to RA LA(-)
I RA(-) to LA() II RA(-) to LL() IIILA(-) to
LL()
Precordial lead is
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• Normal activation

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• Interpretation
• Rhythm look for P waves, regularity,
  reproducible intervals, PR interval, shape
• Rate
• Axis
• Intervals PR, QRS, QTc
• Conduction
• R wave progression
• ST segments and T waves
• Ectopic beats
• Q waves where they should and should not be
• Other stuff

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• Some general guidelines
• P waves
• Best seen in lead II
• Upright or biphasic (neg component smaller) in
  V1-V2, upright in V4-V6
• QRS complex
• V1 shows rS, V6 shows qR
• Size of r wave progressively increases,
  transition V3-V4
• QRS duration lt .120 sec
• One R wave in precordial leads should be gt 8mm
• No R wave in precordial leads gt 27mm
• Sum of tallest R in left leads and S in right
  leads should be lt 35-40mm
• Precordial q waves should not exceed .04 sec nor
  have a depth greater than ¼ the height of the R
  wave following
• R wave in aVL lt12-13mm
• ST segment
• Should not be more than 1mm above or below
  baseline. Normal minor elevation in leads with
  large S waves ( V1-V3) and normal configuration
  is concave up.

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• T waves
• Often inverted in V1. May be inverted in V2 if
  already inverted in V1.
• Always upright in leads I, II, V3-V6
• Always inverted aVL
• U waves
• Amplitude usually lt 1/3 T wave height in same
  lead
• Direction is same as T wave in that lead

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• Axis
• Frontal plane lead with the sum of r wave and s
  wave most closely approximates 0.
• Look at QRS in the lead perpendicular to original
  lead
• If QRS id positive, axis along that direction. If
  negative, axis in opposite direction.

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• Axis- cont

Normal axis
Left axis
Right axis
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• Heart block
• Normal PR interval lt .2 sec
• 1st degree AV block- prolonged PR

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• Heart Block
• 2nd degree AV block- Wenchebach- Mobitz 1
• Prolonged PR until dropped QRS
• 1st PR interval always the shortest
• 1 dropped QRS only
• RR intervals shorten

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• 2nd Degree- 2 to 1 block

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• 2nd degree type 2- mobitz 2

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• Complete heart block

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• Bundle branch block
• QRS gt .120 sec
• RBBB- R-R in V1-V2, s wave in lead 1 V6

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• LBBB
• QRS gt.120 sec
• Neg QRS in V1
• Lack of small q in lead 1, V5-V6

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