Type I AV block, also known as Wenckebach, primarily affects which part of the heart?

Type I AV block, also known as Wenckebach, primarily affects which part of the heart?

• A. Bundle of His
• B. Purkinje fibers
• C. AV node
• D. Sinoatrial node

Answer: (C)

Type I AV block, or Wenckebach, primarily affects the atrioventricular (AV) node. This type of block is characterized by progressive prolongation of the PR interval until a QRS complex is dropped. This pattern indicates a failure of conduction through the AV node, which is responsible for transmitting electrical impulses from the atria to the ventricles. In the case of Wenckebach, the gradual increase in PR interval reflects a problem at the level of the AV node rather than other components of the conduction system. The drop in the QRS complex indicates that an impulse has not been conducted to the ventricles, which also points to the AV node as the site of dysfunction. While the Bundle of His and Purkinje fibers play critical roles in the conduction of impulses after they have passed through the AV node, they are not primarily involved in the conduction delay or failure seen in Type I AV block. Similarly, the sinoatrial (SA) node is responsible for initiating the heartbeat but does not directly relate to the conduction delay associated with Wenckebach. Understanding these distinctions clarifies why the AV node is identified as the primary site affected in Type I AV block.

Type I AV block, or Wenckebach, primarily affects the atrioventricular (AV) node. This type of block is characterized by progressive prolongation of the PR interval until a QRS complex is dropped. This pattern indicates a failure of conduction through the AV node, which is responsible for transmitting electrical impulses from the atria to the ventricles.

In the case of Wenckebach, the gradual increase in PR interval reflects a problem at the level of the AV node rather than other components of the conduction system. The drop in the QRS complex indicates that an impulse has not been conducted to the ventricles, which also points to the AV node as the site of dysfunction.

While the Bundle of His and Purkinje fibers play critical roles in the conduction of impulses after they have passed through the AV node, they are not primarily involved in the conduction delay or failure seen in Type I AV block. Similarly, the sinoatrial (SA) node is responsible for initiating the heartbeat but does not directly relate to the conduction delay associated with Wenckebach. Understanding these distinctions clarifies why the AV node is identified as the primary site affected in Type I AV block.