Atrial Premature Complexes

This is part of: Supraventricular Rhythms

A premature atrial complex (PAC). (In this example the atrial p-wave is difficult to discern).

A premature atrial complex (PAC) with evident negative p-wave

Premature atrial complexes origin from an ectopic pacing region in the atria. They are an example of ectopic beats. The result is a p-wave with often a different morphology as the preceding ones.

A premature atrial complexe is usually followed by a noncompensatory pause caused by the fact that atrial depolarization enters the sinus node and resets the sinus rhythm.

Premature atrial complexes are common and usually benign.

See also: Ventricular Premature Beats Ectopic Beats