Atrial tachycardia

Background

• Also known as focal atrial tachycardia, Paroxysmal Atrial Tachycardia (PAT), unifocal atrial tachycardia, ectopic atrial tachycardia
• Rate >100 bpm
• Electrical focus that originates outside in the sinus node at a single location
  • By comparison, reentrant tachycardias (eg. AVRT, AVNRT) involve multiple foci/ larger circuits
• Sustained atrial tachycardia can lead to a tachycardia-induced cardiomyopathy and it is important not to misdiagnose the rhythm as sinus tachycardia in such cases.
• Atrial tachycardia differs from sinus tachycardia in that the impulses are generated by an ectopic focus somewhere within the atrial myocardium rather than the sinus node.
• The atrial (P wave), is usually 100-250 /min with abnormally shaped P waves. The combination of focal atrial tachycardia with AV block is particularly common in digoxin toxicity.
• Multifocal atrial tachycardia can be mistaken for AF, due to its irregular nature, but closer inspection of the ECG will reveal P waves with at least three different morphologies.

Clinical Features

• Often asymptomatic
• Palpitations
  • Non-specific finding
  • Associated with all tachydysrhythmias, not just AT
  • Rapid fluttering/throbbing/pounding sensation in the chest or neck
• Syncope
  • Patients with AT rarely present with syncope
  • Cerebral hypoperfusion is more common with a ventricular rate >200 bpm
• Chest pain
  • Can present if there is underlying cardiovascular disease
  • Represents a worsening of the associated disease
• Dyspnea
  • Can present if there is underlying cardiovascular disease
  • Represents a worsening of the associated disease

Differential Diagnosis

Narrow-complex tachycardia

• Regular
  • AV Node Independent
    • Sinus tachycardia
    • Atrial tachycardia (uni-focal or multi-focal)
    • Atrial fibrillation
    • Atrial flutter
    • Idiopathic fascicular left ventricular tachycardia
  • AV Node Dependent
    • Paroxysmal supraventricular tachycardia (PSVT)
      • AV node re-entry tachycardia (AVNRT)
      • AV re-entry tachycardia (AVRT)
        • Lown-Ganong-Levine syndrome
        • Wolff–Parkinson–White syndrome
    • Junctional tachycardia
• Irregular
  • Multifocal atrial tachycardia (MAT)
  • Sinus tachycardia with frequent PACs, PJCs, PVCs
  • Atrial fibrillation
    • Atrial fibrillation with RVR
  • Atrial flutter with variable conduction
  • Digoxin Toxicity

Evaluation

P waves inverted in lead II and AVL while upright in III and AVF, suggesting ectopic atrial tachycardia, most likely originating from the left side.

Workup

• ECG

Diagnosis

ECG Features

• Atrial rate >100 bpm
• P-waves
  • Morphology abnormal (when compared with sinus P wave due to ectopic origin)
  • Has at least three consecutive identical ectopic p waves
  • Axis frequently abnormal (e.g. inverted in inferior leads)
• QRS complexes
  • Usually normal morphology (unless pre-existing bundle branch block, accessory pathway, or rate related aberrant conduction)
• Baseline isoelectric (unlike atrial flutter)
• AV block may be present

Management

Unstable

• Cardioversion

Stable

Initial treatment may be aimed at rate control, while resolution of clinical symptoms usually requires definitive treatment and restoration of normal sinus rhythm.

• May cardiovert with adenosine or with beta blockers
• If digoxin toxicity, stop drug and consider Digibind
• Beta blocker or calcium channel blocker for rate control and/or prophylaxis against recurrent episodes

See Also

• Narrow-complex tachycardia

External Links

• https://litfl.com/atrial-tachycardia-ecg-library/