AKA: Paroxysmal Atrial Tachycardia (PAT), unifocal atrial tachycardia, ectopic atrial tachycardia
Atrial Tachycardia Overview
Pathophysiology of 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
ECG Features of Atrial Tachycardia
- 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.
- Poutiainen AM, Koistinen MJ, Airaksinen KE, Hartikainen EK, Kettunen RV, Karjalainen JE, Huikuri HV. Prevalence and natural course of ectopic atrial tachycardia. Eur Heart J. 1999 May;20(9):694-700. PMID: 10208790
- Brady WJ, Truwit JD. Critical Decisions in Emergency and Acute Care Electrocardiography
- Hampton, JR. The ECG In Practice, 6e
- Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric, 6e
- Wagner, GS. Marriott’s Practical Electrocardiography 12e
- Chan, TC. ECG in Emergency Medicine and Acute Care
- Mattu, A. ECG’s for the Emergency Physician
LITFL Further Reading
- ECG BASICS — Waves, Intervals, Segments and Clinical Interpretation
- ECG A to Z by diagnosis –alphabetical diagnostic approach to the ECG
- ECG CLINICAL CASES — ECG’s placed in clinical context with a challenging Q&A approach
- 100 ECG Quiz — Self-assessment tool for examination practice
- ECG Reference SITES and BOOKS — the best of the rest
- LITFL ECG IMAGE Database — Searchable database of LITFL ECG’s
- ECG and Cardiology Eponymous Syndromes — Cheats guide to eponymous emancipation
- ECG Exam Template — a framework for answering ECG exam questions.