Advanced Cardiovascular Life Support (ACLS) Practice Exam

Which rhythm is characterized by a regular heart rate originating from the sinoatrial node?

1. Normal sinus rhythm

2. Second degree AV block Mobitz Type 2

3. Monomorphic ventricular tachycardia

4. Third degree AV block

The correct answer is: Normal sinus rhythm

The rhythm characterized by a regular heart rate originating from the sinoatrial (SA) node is known as normal sinus rhythm. In normal sinus rhythm, the electrical impulses that trigger the heartbeat are generated by the SA node, which is located in the right atrium of the heart. This leads to a consistent heart rate typically ranging from 60 to 100 beats per minute, and the P waves precede each QRS complex, indicating that the impulses are conducted through the atrioventricular (AV) node in a normal manner. In contrast, conditions such as second-degree AV block Mobitz Type 2 and third-degree AV block involve interruptions in the conduction pathway, resulting in varied heart rates or missed beats. Monomorphic ventricular tachycardia arises from an ectopic focus in the ventricles, leading to a rapid heart rate that is not initiated by the SA node. Therefore, normal sinus rhythm distinctly represents the regular and organized activity originating from the natural pacemaker of the heart.