AKA paroxysmal atrial tachycardia (PAT), unifocal atrial tachycardia, ectopic atrial tachycardia
- Usually due to single ectopic focus.
- The underlying mechanism can involve reentry, triggered activity or increased automaticity.
- May be paroxysmal or sustained.
- Multiple causes including digoxin toxicity, atrial scarring, catecholamine excess, congenital abnormalities; may be idiopathic.
- Sustained atrial tachycardia may rarely be seen and can progress to tachycardia-induced cardiomyopathy
- Atrial rate > 100 bpm.
- P wave morphology is abnormal when compared with sinus P wave due to ectopic origin.
- There is usually an abnormal P-wave axis (e.g. inverted in the inferior leads II, III and aVF)
- At least three consecutive identical ectopic p waves.
- QRS complexes usually normal morphology unless pre-existing bundle branch block, accessory pathway, or rate related aberrant conduction.
- Isoelectric baseline (unlike atrial flutter).
- AV block may be present — this is generally a physiological response to the rapid atrial rate, except in the case of digoxin toxicity where there is actually AV node suppression due to the vagotonic effects of digoxin, resulting in a slow ventricular rate (“PAT with block”).
Ectopic atrial tachycardia:
- There is a narrow complex tachycardia at 120 bpm.
- Each QRS complex is preceded by an abnormal P wave — upright in V1, inverted in the inferior leads II, III and aVF.
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- Surawicz B, Knilans TK. Chou’s Electrocardiography in Clinical Practice. 6th Edition. Saunders Elsevier 2008.
- Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.
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