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first-degree atrioventricular (AV) block
First-degree AV block generally results from a delay of impulse propagation through the AV node. Less frequently, a delay of impulse propagation through the atrium or the His-Purkinje system (bundle branch block) is the culprit.
Etiology:
1) increased vagal tone
2) antiarrhythmic agents
3) electrolyte abnormalities
4) myocardial ischemia
5) conduction system disease
Clinical manifestations:
1) generally asymptomatic
2) may exacerbate CHF
Special laboratory:
- electrocardiogram: PR interval >200 ms
Complications:
- need for pacemaker implant (HR=3) [2]
- atrial fibrillation (HR=2) [2]
- increased all-cause mortality (HR=1.4) [2]
Management:
1) therapy not indicated in asymptomatic patient
- bifascicular block not an indication for pacemaker [3]
2) correct electrolyte abnormalities
3) discontinue pharmacologic agents that affect AV conduction
General
atrioventricular (AV) block
References
- Manual of Medical Therapeutics, 28th ed, Ewald &
McKenzie (eds), Little, Brown & Co, Boston, 1995, pg 139
- Cheng S et al
Long-term Outcomes in Individuals With Prolonged PR Interval
or First-Degree Atrioventricular Block
JAMA. 2009;301(24):2571-2577.
PMID: 19549974
http://jama.ama-assn.org/cgi/content/short/301/24/2571
- Medical Knowledge Self Assessment Program (MKSAP) 17, 18,
American College of Physicians, Philadelphia 2015, 2018.