What is the treatment for multifocal atrial tachycardia (MAT)?

Treatment for Multifocal Atrial Tachycardia (MAT)

Intravenous metoprolol or verapamil are the first-line pharmacological treatments for acute management of multifocal atrial tachycardia, while oral verapamil, diltiazem, or metoprolol are recommended for long-term management of recurrent symptomatic MAT. 1

Understanding MAT

Multifocal atrial tachycardia is characterized by:

• At least 3 distinct P-wave morphologies on ECG
• Atrial rate >100 bpm
• Distinct isoelectric period between P waves
• Variable P-P, P-R, and R-R intervals

Treatment Algorithm

Step 1: Address Underlying Conditions

• MAT is commonly associated with:

  • Pulmonary disease and pulmonary hypertension
  • Coronary artery disease
  • Valvular heart disease
  • Electrolyte abnormalities (especially hypomagnesemia)
  • Theophylline therapy 1, 2

• Correction of these underlying conditions is the cornerstone of management 2

Step 2: Correct Electrolyte Abnormalities

• Administer intravenous magnesium even in patients with normal magnesium levels 1, 2
• Consider magnesium sulfate (1-2 g IV) for acute management 3, 4

Step 3: Acute Pharmacological Management

• For hemodynamically stable patients:

  • Intravenous metoprolol (Class IIa, Level C-LD) 1, 5
  • OR
  • Intravenous verapamil (Class IIa, Level C-LD) 1, 6
    • Consider calcium pretreatment (1g calcium gluconate IV) before verapamil to minimize hypotension 6

• Important cautions:

  • Beta blockers should be avoided in:

    • Severe bronchospastic pulmonary disease
    • Acute decompensated heart failure
    • Hemodynamic instability
    • Severe conduction abnormalities
    • Sinus node dysfunction 1

  • Calcium channel blockers should be avoided in:

    • Acute decompensated heart failure
    • Hemodynamic instability
    • Severe conduction abnormalities
    • Sinus node dysfunction 1

Step 4: Long-term Management

• For recurrent symptomatic MAT, use:
  • Oral verapamil (Class IIa, Level B-NR) 1
  • OR
  • Oral diltiazem (Class IIa, Level C-LD) 1
  • OR
  • Oral metoprolol (Class IIa, Level C-LD) 1, 5

Clinical Pearls and Pitfalls

• Cardioversion is not useful in MAT 1, 2
• Antiarrhythmic medications are generally not helpful for suppression of MAT 1, 2
• Verapamil has shown moderate success in terminating MAT (8 of 16 patients in one study) 1, 6
• Metoprolol has been effective in restoring sinus rhythm in patients with MAT and respiratory disease after correction of hypoxia 5
• Amiodarone has been reported as potentially effective in limited studies but is not a first-line treatment 1, 7
• MAT may be difficult to distinguish from atrial fibrillation on physical examination or a single ECG tracing, so a 12-lead ECG is essential for diagnosis 1

Efficacy of Treatments

• Intravenous verapamil: Can convert MAT to sinus rhythm in approximately 50% of patients; otherwise slows ventricular rate 6
• Intravenous/oral metoprolol: Effective in both acute and chronic treatment, with studies showing restoration of sinus rhythm in most patients 5
• Magnesium supplementation: Particularly effective when administered intramuscularly or intravenously, with conversion to sinus rhythm typically occurring within 1-8 hours 4