Multifocal atrial tachycardia (MAT)
What it is and why it matters
Multifocal atrial tachycardia (MAT) is an irregular narrow-complex supraventricular tachycardia caused by three or more competing atrial pacemaker foci. It is most commonly seen in older patients with acute pulmonary disease (particularly COPD exacerbations) and in settings of hypoxia, sepsis, electrolyte disturbance or drug toxicity.
Recognition in the emergency department matters because management focuses on correcting precipitating causes and supportive care rather than routine anticoagulation or rhythm-conversion strategies used for atrial fibrillation.
Pathophysiology
Multiple atrial ectopic foci fire intermittently, producing discrete but different P waves, variable PR intervals and an irregularly irregular ventricular response. Hypoxia and adrenergic stimulation increase automaticity of ectopic atrial pacemakers and are common triggers. MAT is distinct from atrial fibrillation (which lacks organised P waves) and from re-entrant atrial tachycardias.
Typical clinical context and common precipitants MAT is most often associated with:
- Acute pulmonary disease (COPD exacerbation, pneumonia, respiratory failure)
- Hypoxaemia and hypercapnia
- Sepsis and systemic inflammatory states
- Electrolyte abnormalities (hypokalaemia, hypomagnesaemia)
- Sympathomimetic drugs or toxicity (theophylline, inhaled β‑agonists)
- Less commonly: myocardial ischaemia, postoperative or metabolic derangements
Patients usually present with breathlessness, worsening respiratory symptoms or palpitations; underlying pulmonary illness is often the primary issue.