ECG Interpretation

1
ECG Interpretation

• Chapter 22

2
ECG Interpretation

• Rate
• Atrial rate PP interval
• Ventricular rate RR interval
• Rhythm
• P wave
• PR interval
• QRS
• voltage (height)
• width

• Axis
• Hypertrophy
• Blocks
• Infarct
• Ischemia

3
Standardization

• Standardization mark
• 10 mm vertical deflection 1 mVolt

4
Rate

• Ventricular rate (heart rate)
• RR interval
• Atrial rate
• PP interval
• 3rd degree AV block

5
Heart Rate Calculation
1500 divided by the number of small boxes between two R waves most accurate take time to calculate only use with regular rhythms 1 lg sq 300 bpm 2 lg sq 150 bpm 3 lg sq 100 bpm 4 lg sq 75bpm 5 lg sq 60 bpm 6 lg sq 50 bpm
300 divided by the number of large boxes between two R waves quick not too accurate only use with regular rhythm 1 lg sq 300 bpm 2 lg sq 150 bpm 3 lg sq 100 bpm 4 lg sq 75bpm 5 lg sq 60 bpm 6 lg sq 50 bpm
10 multiplied by the number of R waves in 6 seconds less precise use with irregular rhythms very quick 1 lg sq 300 bpm 2 lg sq 150 bpm 3 lg sq 100 bpm 4 lg sq 75bpm 5 lg sq 60 bpm 6 lg sq 50 bpm
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Rhythm

• Sinus rhythm - consistent P waves
• Atrial rhythm - irregular P waves
• Junctional/Nodal rhythm - no P waves, late P
  waves, or inverted P waves
• Ventricular rhythm - no P waves, wide QRS

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AV Junctional Rhythms

• Retrograde P waves immediately preceding the QRS
  complexes in aVR and II.
• Retrograde P waves immediately following the QRS
  complexes
• Absent P waves

8
ECG Waves

• P wave
• atrial depolarization
• 2.5 mm in amplitude
• lt 0.12 sec in width
• PR interval (0.12 - 0.20 sec.)
• time of stimulus through atria and AV node
• prolonged interval first-degree heart block

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P wave

• Tall RAE
• Wide LAE

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PR Interval

• Long PR interval first degree AV block
• Short PR interval WPW
• Short PR interval with inverted P waves ectopic
  atrial or junctional pacemaker

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Classification of AV Heart Blocks
Degree AV Conduction Pattern
1St Degree Block Uniformly prolonged PR interval
2nd Degree, Mobitz Type I Progressive PR interval prolongation
2nd Degree, Mobitz Type II Sudden conduction failure
3rd Degree Block No AV conduction
12
Wolff-White-Parkinson

• Wide QRS
• due to early depolarization
• not due to a delay in depolarization
• Shortened PR interval
• Upstroke QRS complex is slurred delta wave

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ECG Waves

• QRS
• width 0.12 second or less

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Normal QRS
V6?
V6?
V1?
V1?
Fig. 4-6
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Normal Q waves

• Septal r wave

• Septal q wave

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Q Waves

• Abnormal if wider than 0.04 sec
• Leads I, II, III, aVf or leads V3 - V6.
• Greater than 25 of the R wave
• Note Not all Q waves are abnormal, Not all Q
  waves are the result of MI.

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QRS Width

• Wide
• RBBB or LBBB
• Premature ventricular beats
• WPW

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QRS Voltage

• RVH
• LVH

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Mean QRS Axis
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Axis Deviation
LEAD I LEAD aVF (or Lead II or III) LEAD aVR
Normal Positive Positive
LAD Positive Negative
RAD Negative Positive Positive (or Negative)
Intermediate axis Negative Negative
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R Wave Progression
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Transmural MI
Ischemia Tall T waves (and/or reciprocal T wave inversion)
Injury ST segment elevation. T wave inversion of the previously tall T waves
Infarct Pathalogical Q waves (at least one small box wide or 11/3 the entire QRS height)
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Overview
LEAD AREA OF THE HEART
V1-V2 Anterior/Septum
V3-V4 Anterior Wall
V5-V6 Anterior/Lateral
II, III, aVF Inferior
I and aVL Lateral
V1-V2 Posterior (reciprocal)
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ST Segments

• J point
• end of QRS wave
• beginning of ST segment
• ST segment
• beginning of ventricular repolarization
• normally isoelectric (flat)
• changes, elevation or depression, may indicate
  pathological condition

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Subendocardial Ischemia

• ST segment depression criteria
• 1 mm or more
• horizontal or downward
• lasts 0.08 seconds
• depression of only the J point with rapid upward
  sloping are considered normal.