Diagnosic criteria

  Since atrial depolarization is from left atrium to right atrium, the P wave is positive in lead I (to which it is approaching) and negative in lead V6.

  On the frontal plane, P wave axis is between +90 and +270 degrees.

  Some patients also have a dome-and-dart appearance of the P wave in leads V1 and V2.



References

  Am Heart J 1982;103:848-852.

  Am J Cardiol 1966;17:203-210.

  Circulation 1983;68:701-706.




ECG 1. The ECG above, belongs to a 45 years-old man with left atrial rhythm.

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ECG 2. The above ECG is from an old man with old inferior and old anterior myocardial infarctions.
Coronary angiography showed 3-vessel (extensive) coronary artery disease.
QT interval prolongation is seen.
The P wave is positive in lead I and negative in lead C6: left atrial rhythm.

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