premature atrial complex (PAC, atrial premature contraction, APC)

Introduction

Premature Atrial Complex (PAC) are atrial depolarizations* that occur prior to arrival of the impulse originating in the sinus node. Most commonly they result from abnormal automaticity, but may occur as a result of intra-atrial re-entry.

* with resultant premature atrial contraction

Etiology

• infection
• inflammation
• myocardial ischemia
• drug toxicity
• catecholamine excess
• electrolyte imbalance
• tobacco
• alcohol
• caffeine

Clinical manifestations

• patients may be asymptomatic
• feeling of skipped beats

Diagnostic procedures

• electrocardiogram:
• p-wave appears earlier than expected & with different morphology (contour & axis) than the sinus-initiated p-wave
• PR interval following the PAC may be slightly prolonged
• generally a compensatory pause between PAC & next sinus- initiated p-wave

Management

• asymptomatic patients require no therapy
• symptomatic individuals
  • therapy directed towards the underlying preciptiating factor(s)
    • offending drugs
    • electrolyte abnormalities
  • beta-adrenergic receptor antagonists
  • Ca+2-channel blockers

More general terms

• premature electrocardiography complex