ECG Interpretations

ECG interpretations

Normal Impulse Conduction

• Sinoatrial node
  • ↓
• AV node
  • ↓
• Bundle of His
  • ↓
• Bundle Branches
  • ↓
• Purkinje fibers

The “QRST”

• P wave - Atrial
  depolarization
• QRS - Ventricular
  depolarization
• T wave - Ventricular
  repolarization

Rhythm Analysis

• Step 1: Calculate rate.
• Step 2: Determine regularity.
• Step 3: Assess the P waves.
• Step 4: Determine PR interval.
• Step 5: Determine QRS duration.

Step 1: Calculate Rate

• R wave

• Option 2

  • Find a R wave that lands on a bold line.
  • 300/ large box

Step 5: QRS duration

• Normal: (1 - 3 boxes)

Arrhythmia Formation

• Sinus node = brady / tachy
• Atrial cells = supraventricular
• AV junction = supraventricular
• Ventricular cells

Supraventricular arrhythmia

Atrial cells can:

• fire from a focus
• a looping re-entrant circuit

Atrial Flutter

Atrial Cell Problems

Atrial Fibrillation

Ventricular Cell Problems

• Premature Ventricular Contractions (PVCs)
• Ventricular Fibrillation
• Ventricular Tachycardia

Rhythm #1

• Rate?
  • 30 bpm
• Regularity?
  • regular
• P waves?
  • normal
• PR interval?
  • 0.12 s
• QRS duration?
  • 0.10 s

Interpretation? Sinus Bradycardia

Sinus Bradycardia

• Deviation from NSR
  • Rate
    • < 60 bpm

Rhythm #2

• Rate? 130 bpm
• Regularity? regular
• P waves? normal
• PR interval? 0.16 s
• QRS duration? 0.08 s

Interpretation? Sinus Tachycardia

Rhythm #5

• Rate?
  • 100 bpm
• Regularity?
  • irregularly irregular
• P waves?
  • none
• PR interval?
  • none
• QRS duration?
  • 0.06 s

Interpretation? Atrial Fibrillation

Atrial Fibrillation

• Deviation from NSR

Rhythm #6

Atrial flutter

• Rate more than 250 up to 320 b/min.
• Sawtooth pattern on ECG.
• Associated with organic heart disease.

Interpretation? Atrial Flutter

Ventricular Fibrillation

• Rhythm: irregular-coarse or fine, wave form varies in size and shape
• Fires continuously from multiple foci
• No organized electrical activity
• No cardiac output
• Causes:
  • MI
  • ischemia
  • untreated VT
  • underlying CAD
  • acid-base imbalance
  • electrolyte imbalance
  • hypothermia

Ventricular Tachycardia

• Ventricular cells fire continuously due to a looping re-entrant circuit
• Rate usually regular, 100 - 250 bpm
• P wave: may be absent, inverted or retrograde
• QRS: complexes bizarre, > .12
• Rhythm: usually regular

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