Electrocardiogram Rhythm Interpretation

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Electrocardiogram Rhythm Interpretation

• by
• Evan M. Hodell 12/00

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What is an EKG?

• An EKG is a method of measuring, displaying and
  recording the electrical activity of a heart
• Electrical stimuli is amplified to create a
  rhythm strip by a machine that consistently
  produces representations of the hearts
  electrical activity

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BASIC TERMINOLOGY

• Arrhythmia Abnormal rhythm
• Baseline Flat, straight, isoelectric line
• Waveform Movement away from the baseline, up
  or down
• Segment A line between waveforms
• Interval A waveform plus a segment
• Complex Combination of several waveforms

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Electrical System of Heart
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Components of a NSR
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Components of a NSR
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Point of Origin Name

• SA Node- Sinus rhythm
• Causes regular, rounded P waves, and normal,
  narrow QRS complexes
• Atria- Atrial rhythm
• Causes irregularly shaped P waves, but still
  normal, narrow QRS complexes
• AV Node- Junctional rhythm
• Normal, narrow QRS complexes with no P waves
• Perkinjie Fibers- Ventricular rhythm
• No P waves, and irregular, wide QRS complexes

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Beginning to Recognize Rhythms

• Step 1 Are there P waves?
• Step 2 Are there QRS complexes?
• Step 3 Are the P waves and QRS complexes
  related?

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Example 1

• STEP 1.
• Are there P waves?

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Example 1 Continued

• Are there P waves?
• Yes, P waves are easily identifiable and regular
  in rate.

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Example 1 Continued

• STEP 2.
• Are there QRS complexes?

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Example 1 Continued

• STEP 2.
• Yes there are normal, narrow, QRS complexes.

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Example 1 Continued

• STEP 3
• Are they related, 11?

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Example 1 Continued

• STEP 3
• Are they related, 11?
• Yes, there is one P wave for every QRS.
• This is called a sinus rhythm

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Example 2

• Follow steps 1-3 as demonstrated in Ex. 1.
• This is also a sinus rhythm.
• Note The P waves are smaller, yet their
  regularity in relation to the QRS complexes gives
  them away.

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Example Three

• Following the same steps, this one doesnt match
  up!?!?

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Example 3 continued

• Step 1
• Are there P waves?
• Yes,
• Note notice the dotted arrows indicate the
  location of P waves buried in the stronger
  electrical activity of the QRS complexes.

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Example 3 Continued

• STEP 2
• Are there QRS complexes?
• Yes, there are normal, narrow QRS complexes.

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Example 3 Continued

• STEP 3.
• Are they related?
• NO, they are both regular in shape and rate, but
  there is no relation between them.
• This shows a Complete Heart Block, also called a
  3rd degree block.
• Can the Heart effectively pump blood if the Atria
  and Ventricles are not working together?

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Case Study of Beau

• Beau is an 11 y/o 45 lb. Male Australian
  Shepard.
• Physical exam see overhead
• Beau presents with a moderate, chronic, nocturnal
  cough with mild dyspnea. Secondary exam also
  reveals a pounding irregular heartbeat and Grade
  4 murmur.
• Electrocardiogram was ordered in addition to
  other tests. Result

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Case Study of Beau

• EKG reveals a Sinus Arrhythmia,
• Beaus heart is firing off Premature Atrial
  Contractions, PACs.
• Potentially indicative of atrial enlargement, or
  other heart irritability, which may or may not be
  related to Beaus cough and current presentation.

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4. Normal Intervals for the Human, Dog and Cat

• Human- HR- 60-100 bpm
• PR interval- 0.12-0.20 sec
• QRS width max 0.11 sec
• QT interval 0.36-0.44 sec
• Dog- HR- 60-220 bpm
• PR interval 0.06-0.13 sec
• QRS width max 0.06 sec for large 0.05 sec
  for small
• QT interval 0.15-0.25 sec
• Cat- HR 120-240 bpm
• PR interval 0.05-0.09 sec
• QRS width max 0.04 sec
• QT interval 0.12-0.18 sec
• -Tilley L.P. et al 1995

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References

• Aehlert RN Ph. ECGs Made Easy, Mosby Year Book
  1995
• Bledsoe, B. Brady Paramedic Emergency Care,
  Prentice Hall New Jersey, 1988
• Foster, Bruce D.O. Twelve-Lead
  Electrocardiography for the ACLS Provide,
  Waynesboro PA, W.B. Saunders Co., 1996
• Fox. P.R. and Kaplan P. Contemporary Cardiology
  Issues in Small Animal Practice, Churchill
  Livingston, New York 1987
• Smith F.W.K, D.J. Hallock, Manual of Canine and
  Feline Cardiology W.B. Saunders, Philadelphia
  1995
• Tilley, L.P. Essentials of Canine and Feline
  Electrocardiography, 3rd edition Williams
  and Wilkins, Baltimore 1995