An atrial ectopic rhythm is a rhythm where the impulse formation in the atrium is coming from the wrong place. (Ectopic means out of place or from the wrong place.) In the example above, the first P wave is upright, the second one upright and slightly smaller, the third smaller yet with the 4th and 5th ones barely visible. This suggests that the first P wave may have come from the SA node, but that the following ones come from different locations in the atria, thus causing their shape and the PR interval to change. Atrial ectopic rhythms may also have rate changes along with the changes described above in the P waves and PR intervals. The heart rate in the above example is 63 beats per minute with the PR interval varying from .16 seconds to .06 seconds.
Atrial ectopic rhythms are most commonly found in younger patients and are generally benign. Patients will frequently describe their symptoms as a change in rate. Treatment is generally not indicated.