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# Third Degree Heart Block ECG Interpretation #316

## Description Part 1

• Third Degree Heart Block is also known as “Complete Heart Block”.
• This name more accurately describes the electrical event or problem occurring within the heart.
• As a result of disease or tissue death, there is a blockage preventing electrical impulses within the atria from entering the ventricular conduction system.
• The outcome of 3rd degree heart block ECG are two independently functioning pacemakers within the heart (typically one is supraventricular, the other is ventricular).
• Essentially, the atria and ventricles are electrically separated (dissociated) from one another.

## Description Part 2

• What will be seen are regularly occurring P waves and QRS complexes, but at two distinctly different rates.
• The QRS complexes may occur as a result of impulses coming from the His bundle or the Purkinje network.
• Morphology and rate will often provide clues regarding the locus of ventricular impulse stimulation. A more narrow appearing QRS with a rate greater than 40 generally would indicate the impulse formation is coming from the His bundle. A wide, bizarre QRS with a rate of 40 or less indicates the impulses are originating in the Purkinje network.
• Complete heart block presents with Regular P to P and R to R intervals and a variable P-R interval.

## ECG Practice Strip

Analyze this tracing using the five steps of rhythm analysis.

• Rhythm: Atria and Ventricles - Regular
• Rate: Atria – 94, Ventricles - 34
• P Wave: Upright (some buried)
• PR interval: Variable
• QRS: 0.14 sec
• Interpretation: Third Degree (Complete) Heart Block

Authors and Sources

## Sources

? v:3 | onAr:0 | onPs:2 | tLb:0 | pv:1
uStat: False | db:0 | cc: | tar: False
| cDbLookup # 0 | pu: False | pl: System.Collections.Generic.List`1[System.String]
em: | newuser: False

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