Atrial tachycardia

Background

• Also known as focal 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

Clinical Features

• 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

. 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 usually100-250 /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.

Management

• Non-sustained episodes of focal tachycardia are commonly seen on ambulatory ECG monitoring and are often asymptomatic.

• 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.

• Focal atrial tachycardia should be treated with urgent electrical cardioversion if the patient is unstable.

• Stable patients may cardiovert with adenosine or with beta blockers.

• If digoxin toxicity is the cause of the atrial tachycardia the drug should be stopped.

• Rate control and or prophylaxis against recurrent episodes can be attained usually with beta blockers, or calcium channel blockers.