Atrial Tachycardia (AT)

Definition, Etiology, PathogenesisTop

Atrial tachycardia (AT) is a paroxysmal or sustained tachycardia originating in the atrium outside the sinus node. AT may be divided into 2 types:

1) Focal AT: An accelerated (100-250 beats/min) regular rhythm originating in the atrium with a stable P wave morphology. It can occur in patients with or without heart disease.

2) Multifocal AT: An irregular rhythm with ≥3 varying morphologies of the P waves. It is commonly seen in patients with cardiac or lung disease and metabolic or electrolytic disturbances.

Clinical Features and Natural HistoryTop

Symptoms range from mild or nonexistent to severe, depending on the heart rate during tachycardia and presence of an underlying condition. AT sustained over a long period may lead to tachycardia-induced cardiomyopathy. AT does not cause thromboembolic complications but it may trigger atrial fibrillation (AF).

DiagnosisTop

Diagnostic Tests

1. Electrocardiography (ECG): In patients with focal AT, P waves are identical and their shape depends on the location of the anatomical focus (they can also resemble sinus rhythm if coming from a close-by location). In multifocal AT the rhythm is grossly irregular and several morphologies of P waves are seen.

2. Electrophysiologic study (EPS): This is used to establish the exact location of the AT focus and to perform ablation.

Differential Diagnosis

Supraventricular tachycardia: see Figure 2 in Cardiac Arrhythmias. Narrow-QRS tachycardia: see Figure 3 in Cardiac Arrhythmias. Wide-QRS tachycardia: see Figure 4 in Cardiac Arrhythmias.

TreatmentTop

Treatment is more difficult than in the case of atrioventricular nodal reentrant tachycardia and atrioventricular reentrant tachycardia. Effective management of underlying conditions is also important.

Acute Management

1. IV beta-blockers, diltiazem, or verapamil are useful in hemodynamically stable patients.

2. Synchronized cardioversion is recommended for acute treatment in hemodynamically unstable patients.

3. Adenosine can be useful in the acute setting to either restore sinus rhythm (some atrial arrhythmias respond to adenosine) or diagnose the tachycardia mechanism. In the case of AT, atrial arrhythmia may continue during the atrioventricular block induced by adenosine, making the P waves clearly visible. It is important to record an ECG strip during adenosine administration.

Long-Term Management

1. In patients with symptomatic focal AT, catheter ablation is recommended as an alternative to pharmacologic treatment.

2. In patients with focal AT, oral beta-blockers, diltiazem, or verapamil are recommended for ongoing management.

3. Flecainide or propafenone can be effective in patients with no structural heart disease.

4. In multifocal AT catheter ablation is less effective. Oral verapamil or diltiazem are recommended in this case.