What is the Difference Between AV Block 1 and 2?

Atrioventricular (AV) block is a condition in which the electrical impulses between the atria and ventricles of the heart are disrupted, leading to abnormal heart rhythms. There are three main types of AV block: first-degree, second-degree, and third-degree. Second-degree AV block can be further classified into Mobitz type 1 (Wenckebach) and Mobitz type 2, based on the characteristics of the PR interval on an electrocardiogram (ECG).

The differences between AV block 1 (Mobitz type 1) and AV block 2 (Mobitz type 2) are as follows:

1. Progressive PR interval prolongation: In Mobitz type 1 (Wenckebach), there is a progressive prolongation of the PR interval, which eventually culminates in a non-conducted P wave. In contrast, Mobitz type 2 has a constant PR interval without any progressive prolongation.
2. Non-conducted P waves: Mobitz type 1 (Wenckebach) is characterized by intermittent non-conducted P waves without warning. Mobitz type 2, on the other hand, has sporadically occurring blocks without any Wenckebach phenomenon.
3. Location of block: The site of block is indeterminate in Mobitz type 2, while in Mobitz type 1, the block is typically located in the AV node.
4. Clinical significance: Mobitz type 1 (Wenckebach) is often benign, while Mobitz type 2 can be more dangerous and may require a permanent pacemaker.

In summary, the main differences between AV block 1 (Mobitz type 1) and AV block 2 (Mobitz type 2) lie in the progression of the PR interval, the occurrence of non-conducted P waves, the location of the block, and the clinical significance of each type.

Comparative Table: AV Block 1 vs 2

Atrioventricular (AV) block is a disruption in the conduction of electrical impulses from the atria to the ventricles of the heart. It is categorized into three types: AV block 1, AV block 2, and AV block 3. The main difference between AV block 1 and AV block 2 lies in the degree of conduction delay or blockage.

First-degree AV block is characterized by a delay in the conduction of electrical impulses from the atria to the ventricles, while second-degree AV block involves the blocking of conduction of some atrial impulses to the ventricles. On an ECG, AV block 1 is detected by a PR interval greater than 200ms, whereas AV block 2 is detected by the presence of P-waves not followed by QRS complexes.