Diagnostic criteria

  Heart rate is 60-100/minute.

  Every P wave is followed by a QRS complex.

  Since the impulse originates from an ectopic atrial focus the P waves have a different configuration from that of the sinus P wave.

  The recognization of differently shaped P waves in ectopic atrial rhythm may require the inspection of previous ECGs for comparison.

  Sometimes, the P waves may be negative in leads II and III. In this case, the ectopic atrial rhythm is easy to diagnose. This rhythm is usually called as coronary sinus rhythm or low atrial rhythm since the impulse is assumed to originate from the mouth of the coronary sinus.

  It can often be difficult to exactly localize the APC site from the surface ECG because the true P wave shape can be obscured by the T wave and the vagaries of the relationship between cardiac anatomy/position in the chest and the surface.


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ECG 1. Ectopic atrial rhythm in a healthy boy of 14 years old. After 4 beats of ectopic atrial rhythm, the sinus rhythm takes over.
The R-R intervals of the ectopic atrial rhythm are longer than the R-R intervals of the sinus rhythm.

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ECG 2. Negative P waves in leads D2 and D3 show ectopic atrial rhythm.

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ECG 3a. The negative P waves in leads II and III show ectopic atrial rhythm.

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ECG 3b. The ECG was recorded again a few minutes later. This time the rhythm is sinus.
In some patients, ectopic atrial rhyhtm may last for a very short time (seconds or minutes).

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ECG 4. Ectopic atrial rhythm in a 75 years-old man who had undergone coronary artery bypass surgery 2 years ago.
The ectopic atrial focus seems to be inferior and probably midline. His coronary arteries are normal.

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ECG 5. Atrial bigeminal rhythm in a 50 years-old man with normal coronary arteries.
The ectopic atrial focus is probably near the coronary sinus ostium.

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ECG 6. The 3-channel ECG tracings above are from the ambulatory ECG (Holter) recordings of a 17 years-old patient.
The tracings are continuous strips.
A short-lasting episode of ectopic atrial rhythm (with negative P waves) is seen (arrows show the first and the last beats).

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