Third Degree Atrioventricular Block
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Contents |
Etiology
- drug toxicity: digitalis
- myocardial scarring secondary to infarction
- conduction system disease
- infiltrative diseases
- inadvertant surgical interruption of conduction system
- calcific aortic stenosis
- endocarditis
- metastatic disease
- 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
- depends upon underlying escape rhythm
- light-headedness
- dyspnea
- angina
- syncope & near-syncope
Diagnostic-procedures
- electrocardiogram:
- atrial rate exceeds ventricular rate
- atrial/ventricular dissociation
- ventricular escape rhythm is usually regular
Differential-diagnosis
Management
- symptomatic patients
- atropine 0.5-2.0 mg IV
- transcutaneous pacemaker in patients resistant to atropine
- bradycardia refractory to atropine & transcutaneous pacemaker not available
- dopamine 5-20 ug/kg/min
- epinephrine 2-20 ug/min c isoproterenol 2-10 ug/min
More General Terms
Additional Terms
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
