American Allied Health National Certification Practice Exam 2025 - Free Allied Health Certification Practice Questions and Study Guide

A Premature Atrial Contraction (PAC) is characterized by an irregular heart rhythm where atrial contractions occur earlier than expected in the cardiac cycle. This early contraction is due to ectopic impulses originating from an area in the atria other than the sinoatrial node, which can disrupt the normal pacing of the heart. As a result, the rhythm does not follow the regular pattern, leading to an irregularity that is a hallmark of PACs.

The presence of these early impulses causes a noticeable disturbance in the usual sequence of heartbeats, often resulting in the feeling of a skipped beat or palpitations for some individuals. The key point here is that PACs disrupt the expected timing of the atrial contractions. This is why the characteristic of having irregular heart rhythm with atrial contractions occurring prematurely is essential to identifying PACs.

In contrast, a regular heart rhythm with no early contractions would suggest a normal sinus rhythm, while consistent ventricular contractions that occur early would imply a different type of arrhythmia, such as a premature ventricular contraction (PVC). Uniform P waves preceding every QRS complex indicates a normal conduction pattern, where each heartbeat originates from the SA node, rather than indicating the presence of PACs.