Premature atrial contractions
Premature atrial contractions are early beats arising from an ectopic atrial focus, seen on ECG as a premature P wave of abnormal morphology followed by a usually narrow QRS. They are extremely common and usually benign, though a high burden is associated with incident atrial fibrillation and warrants risk-factor management.
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What this article covers
- Overview
Definition: premature atrial contractions (PACs) are early depolarizations originating from an ectopic focus in the atria, appearing as a premature P wave of abnormal morphology followed by a usually narrow QRS.
- Epidemiology
Extremely common, found in most people on prolonged monitoring.
- Risk factors
Age and structural or atrial disease. Stimulants: caffeine, nicotine, alcohol, and sympathomimetics.
- Pathophysiology
Enhanced automaticity or triggered activity in an ectopic atrial focus fires before the next sinus beat.
- Clinical features
Usually asymptomatic. Palpitations, skipped beats, or a fluttering or thumping sensation (often the post-PAC beat).
- Differential diagnosis
Premature ventricular contractions: wide QRS without a preceding premature P wave (premature ventricular contractions).
- Diagnosis
Establish with an ECG showing a premature P wave of abnormal morphology followed by a narrow QRS: the diagnostic basis is a 12-lead ECG or rhythm strip demonstrating an early P wave differing from…
- Management
First-line, reassure and reduce triggers: most patients need only explanation and reduction of caffeine, alcohol, nicotine, and stress, with repletion of potassium to above 4 mmol/L and magnesium to above 2 mg/dL.
- Complications
Symptom burden in a minority. Association with incident atrial fibrillation at high burden.
- Prognosis
Benign in most, with no impact on survival in isolation.
- Prevention
Limit caffeine, alcohol, and nicotine. Maintain sleep and manage stress.
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