What is the Difference Between Mobitz 1 and 2?

Mobitz type 1 and type 2 are both subtypes of second-degree atrioventricular (AV) block, which is an irregular cardiac rhythm reflecting a conduction block in the electrical system of the heart. The main differences between Mobitz type 1 and type 2 are:

1. Gradual prolongation of PR intervals: In Mobitz type 1, the PR interval gradually lengthens before a block occurs, while in Mobitz type 2, the PR intervals are constant and not prolonged.
2. Prognosis: Mobitz type 1 is generally benign and reflects a block at the AV node, often indicating a better prognosis. In contrast, Mobitz type 2 reflects a block after the AV node, either at the bundle of His or its branches, and often results in a poorer prognosis, as it has a higher risk of progressing to third-degree AV block.
3. Causes: Mobitz type 1 can occur as a result of reversible conduction block caused by metabolic factors, while Mobitz type 2 is typically associated with a more serious underlying issue, such as heart disease.

To differentiate between Mobitz type 1 and type 2, if there is a gradual prolongation of PR intervals before a block, Mobitz type 1 should be diagnosed. If the PR intervals are constant but varying, Mobitz type 1 should still be diagnosed. If the PR intervals are constant and not prolonged, Mobitz type 2 should be diagnosed.

Comparative Table: Mobitz 1 vs 2

Mobitz 1 and Mobitz 2 are the two primary types of second-degree heart block, which is a condition where there is a delay in the transmission of impulses through the atrioventricular (AV) node. The main difference between Mobitz 1 and Mobitz 2 lies in the behavior of the PR interval and the block's prognosis. Here is a comparison table of the two types:

In Mobitz 1, the PR interval progressively lengthens with each beat until the atrial impulse is not conducted, and AV nodal conduction resumes with the next beat. In contrast, Mobitz 2 has a constant PR interval, and beats are intermittently non-conducted, usually in a repeating cycle of every 3rd (3:1 block) or 4th (4:1 block) P wave. Mobitz 1 is generally considered benign and may indicate AV node obstruction, while Mobitz 2 has a worse prognosis and is more likely to progress to a third-degree block.