Premature Atrial Contractions

Rate	normal or accelerated
P wave	usually have a different morphology than sinus P waves because they originate from an ectopic pacemaker
QRS	normal
Conduction	normal, however the ectopic beats may have a different P-R interval.
Rhythm	PAC's occur early in the cycle and they usually do not have a complete compensatory pause.

PAC's occur normally in a non diseased heart.

However, if they occur frequently, they may lead to a more serious atrial dysrhythmias.
They can also result from CHF, ischemia and COPD.

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With PACs, all the P waves look identical.