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third-degree atrioventricular (AV) block (complete heart block)
Etiology:
1) drug toxicity: digitalis
2) myocardial scarring secondary to infarction
3) conduction system disease
4) infiltrative diseases
a) amyloidosis
b) sarcoidosis
5) rheumatologic disorders
a) polymyositis
b) scleroderma
c) rheumatoid nodules
6) infectious diseases
a) Chagas' disease
b) Lyme disease
7) inadvertant surgical interruption of conduction system
8) calcific aortic stenosis
9) endocarditis
10) metastatic disease
11) Stokes-Adams-Morgagni syndrome
Pathology:
- absence of transmission of atrial impulses to the ventricles
- in congenital heart block, the site of conduction block is within the AV node
- in acquired heart block, the conduction block is within the His bundle or Purkinje system
Clinical manifestations:
1) depends upon underlying escape rhythm
2) light-headedness
3) dyspnea
4) angina
5) syncope & near-syncope
Special laboratory:
- electrocardiogram:
a) atrial rate exceeds ventricular rate
b) atrial/ventricular dissociation
c) ventricular escape rhythm is usually regular
Differential diagnosis:
- competitive AV dissociation
Management:
1) symptomatic patients
a) transcutaneous pacemaker first priority
- transvenous pacemaker second priority
b) atropine 0.5-2.0 mg IV
- unlikely to be of benefit in wide-complex bradyarrhythmias
c) bradycardia refractory to atropine & transcutaneous pacemaker not available
- dopamine 5-20 ug/kg/min
- epinephrine 2-20 ug/min
- isoproterenol 2-10 ug/min
2) permanent pacemaker for all patients with 3rd degree AV block
Related
Stokes-Adams-Morgagni syndrome
General
atrioventricular (AV) block
hemodynamic instability (compromise)
References
- Manual of Medical Therapeutics, 28th ed, Ewald &
McKenzie (eds), Little, Brown & Co, Boston, 1995, pg 140
- Saunders Manual of Medical Practice, Rakel (ed), WB Saunders,
Philadelphia, 1996, pg 271.
- Medical Knowledge Self Assessment Program (MKSAP) 14,
American College of Physicians, Philadelphia 2006