Advanced Cardiovascular Life Support (ACLS) Practice Exam

What condition represents a complete block in the conduction between the atria and ventricles?

1. Second degree AV block Type 1 Wenckebach

2. Normal sinus rhythm

3. Third degree AV block

4. Monomorphic ventricular tachycardia

The correct answer is: Third degree AV block

Third degree AV block, also known as complete heart block, is characterized by a complete failure of conduction between the atria and the ventricles. In this condition, the atrial impulses are not transmitted to the ventricles at all. As a result, the two chambers beat independently of each other; the atria may beat at their normal intrinsic rate, while the ventricles often rely on a slower escape rhythm to maintain some degree of cardiac output. The lack of coordination between the atrial and ventricular contractions can lead to significant symptoms and hemodynamic instability, making it a critical condition that requires immediate medical intervention. In contrast, other options describe different scenarios of AV conduction disturbances. For instance, second degree AV block Type 1, also known as Wenckebach, features progressive lengthening of the PR interval until a beat is dropped, which indicates partial block rather than complete cessation. Normal sinus rhythm represents effective and coordinated atrial and ventricular activity without any conduction disturbances. Monomorphic ventricular tachycardia refers to a rapid heart rhythm originating from the ventricles, but does not imply a block in the conduction between the atria and ventricles.