C o m p e t e n c e i n E C G D i a g n o s e s

Lesson VI - ECG Conduction Abnormalities
1. Slowing of the primary pacemaker (i.e., SA node); subsidiary
escape pacemaker takes over by default:
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2. Acceleration of a subsidiary pacemaker faster than sinus rhythm;
takeover by usurpation:
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3. 2 nd or 3 rd degree AV block with escape rhythm from junctional
focus or ventricular focus:
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In the above example of AV dissociation (3 rd
degree AV bock with a junctional escape
pacemaker) the PP intervals are alternating
because of ventriculophasic sinus arrhythmia
(phasic variation of vagal tone in the sinus node
depending on the timing of ventricular
contractions and blood flow near the carotid
sinus).
4. Intraventricular Blocks
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