Certified Rhythm Analysis Technician (CRAT) Practice Exam 2026 - Free CRAT Practice Questions and Study Guide

A complete heart block, also known as third-degree atrioventricular (AV) block, is characterized by a lack of communication between the atria and the ventricles. In an ECG reading, this is visually represented by the disassociation between P waves and QRS complexes. Each of these components can occur independently of one another, reflecting a situation where the atrial impulses (P waves) are not conducted to the ventricles.

Typically, in complete heart block, the P waves may occur at a regular rhythm but do not correlate with the ventricular contractions (QRS complexes), which can occur at a different rate driven by a secondary pacemaker in the ventricles. This separation is critical in diagnosing a complete heart block as it indicates a failure in the conduction system that prevents coordinated heart activity.

The other options describe conditions that do not align with the phenomenon seen in complete heart block. For instance, equal intervals between P-P and R-R rhythms suggest a normal relationship between atrial and ventricular activity, which would contradict a complete block. Variability in P-R intervals is more indicative of other types of blocks, such as Mobitz type I, where P waves intermittently fail to conduct to the ventricles but are not fully dissociated.