Certified Rhythm Analysis Technician (CRAT) Practice Exam

In third-degree AV block, there is a complete failure of conduction between the atria and the ventricles. This results in the atrial impulses not being transmitted to the ventricles, leading to a disconnection between the two chambers. As a result, the atria and ventricles beat independently of each other, which is why the conduction of the atrial impulse fails to reach the ventricle.

In this situation, the atria continue to contract at a rate that is determined by the sinoatrial (SA) node, while the ventricles rely on an escape rhythm, which is often slower and takes over when the normal conduction pathway is disrupted. This characteristic makes third-degree AV block distinct and highlights the importance of understanding the relationship between atrial and ventricular electrical activity in cardiac function.

Understanding this concept is crucial for a Certified Rhythm Analysis Technician, as it helps in the identification and differentiation of various types of AV block during rhythm analysis.