Causes

  Atrial bigeminy

  3:2 atrioventricular (AV) block

  Atrial flutter with alternating two different levels of block (i.e. 2:1 and 4:1 block).





ECG 1. Atrial bigeminal rhythm in a young woman.
Every P wave originating from the sinus node is followed by a premature
P wave originating from an ectopic focus
in the atria. The premature P wave is negative in the above ECG, suggesting a
low atrial focus. However, all atrial premature beats should NOT necessarily be negative. Negativity of the P wave is related to
its focus, but not to its prematurity.

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ECG 2. Atrial flutter. Two different ratios of block alternate. The block varies regularly.

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