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: Ahmed Elsaiey, MBBCH [2], Cafer Zorkun, M.D., Ph.D. [3]

Overview

Pathophysiology

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 of the AV node and His-Purkinje system.
One of the characteristics of first degree AV block 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, in majority of cases, results from atrial or AV nodal delay. Other probable sites include the bundle of His and infra-Hisian conduction system.

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.

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[pmid30105427-1] 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.

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