Atrial tachycardia, or focal atrial tachycardia, is result of a micro-reentrant circuit or an automatic focus. The atrial rate is greater than 100 bpm.
Atrial Tachycardia

Examples

Atrial Tachycardia
The normal P wave axis is down in lead V1 and up in lead II. The abnormal P wave axis in this ECG reveals an ectopic atrial source.References
- Link MS. Evaluation and Initial Treatment of Supraventricular Tachycardia. New England Journal of Medicine. 2012;367(15):1438-1448.