What type of conduction abnormality does a PAC indicate?

A premature atrial contraction (PAC) signifies an early contraction originating in the atria, which is why the choice indicating this is correct. PACs occur when ectopic electrical impulses are generated in the atrial tissue, leading to an early depolarization of the atria before the normal sinus node has had a chance to trigger the next heartbeat. This results in an irregular rhythm characterized by an early P wave on the electrocardiogram (ECG), followed by a normal QRS complex and a subsequent pause.

This understanding of PACs emphasizes their role in reflecting atrial activity rather than any problems associated with ventricular conduction, conduction delays through the AV node, or regular atrial activation. The PAC is a specific manifestation of atrial ectopic activity and is often considered a benign finding, although it can serve as a precursor to other types of arrhythmias in some patients.