Premature Atrial Complex (PAC) 

Sinus with PACs

An atrial depolarization that occurs earlier than expected. It is indicated electrocardiographically by an early Pwave followed by a normal QRS complex. PACs may be the result of atrial enlargement or ischemia or may be caused by stress, caffeine, or nicotine. Mosby (2009-02-11).


Rate 60-100 BPM

Rhythm Regular with premature beats 

P-Waves Premature, upright in lead 2. A P wave before every QRS complex. Often differ in shape from sinus P waves.

PR Interval May be normal or prolonged. 

QRS Duration Usually 0.10 seconds (2 1⁄2 small boxes) or less but may be wide or absent depending on the prematurity of the beat.


Monitor Diagnostic 12 lead 

Usually requires no treatment



Noticeable by: 

Occurring earlier than the next expected beat 

© Matt Dillard 2012