First degree AV block pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mohammed Salih, M.D., Ahmed Elsaiey, MBBCH [2], Cafer Zorkun, M.D., Ph.D. [3]
Overview
The atrioventricular node is a normal electrical pathway between the atria and ventricles and it is located in the right atrium. First-degree AV block pathogenesis can be attributed to an electrical conduction delay in the AV node or His-Purkinje system. First-degree AV block can be associated with normal QRS complex or wide QRS complex on the ECG.
Pathophysiology
Physiology
- The atrioventricluar node is the normal electrical pathway between the atria and ventricles. It is located in the right atrium near to the tricuspid valve leaflet.
- The AV node receives blood supply from the right coronary artery in most of the population.
- The bundle of His is the electrical connection between the AV node to the interventricular septum. At the end of the septum, a bundle of His is divided into the right and left bundle branches to the ventricular walls.
Pathogenesis
- First-degree AV block broadly means the prolongation of the PR interval on the ECG with normal atrioventricular node function.
- First-degree AV block pathogenesis can be attributed to an electrical conduction delay in one of the following:[1]
- Atrioventricular node
- His-Purkinje system which is formed of both bundle of His and Purkinje fibers
- The conduction delay can be also in both the AV node and His-Purkinje system.
- One of the characteristics of first-degree AV block is that there are no beats skipped and it has a regular rhythm.
First-degree AV Block with Normal QRS Duration
First-degree AV block with normal QRS duration results from atrial or AV nodal delay.
First-degree AV Block with Wide QRS Complex
First-degree AV block with wide QRS complex most often results from delay in conduction in the bundle of His and in some patients, the AV node.
References
- ↑ Lewalter T, Pürerfellner H, Ungar A, Rieger G, Mangoni L, Duru F; et al. (2018). ""First-degree AV block-a benign entity?" Insertable cardiac monitor in patients with 1st-degree AV block reveals presence or progression to higher grade block or bradycardia requiring pacemaker implant". J Interv Card Electrophysiol. 52 (3): 303–306. doi:10.1007/s10840-018-0439-7. PMID 30105427.