Mobitz type 1 second-degree atrioventricular (AV) block (Wenckebach)
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Etiology
- increased vagal tone
- antiarrhythmic agents
- electrolyte abnormalities
- myocardial ischemia or infarction (inferior wall)
- conduction system disease
Pathology
- progressive delay in AV conduction prior to a conduction block
- in the setting of a normal-appearing QRS complex, type 1 2nd degree AV block is a benign arrhythmia
- rarely progresses to 3rd degree AV block (complete heart block)
Clinical manifestations
- usually asymptomatic
- may be transient
- dizziness, presyncope, syncope
Laboratory
- electrocardiogram:
- gradual PR elongation preceding a non-conducted p-wave
- QRS complexes appear in regular groupings, i.e. as in bigeminy, trigeminy
- shortest PR interval occurs with first p-wave following a blocked p-wave
- RR interval shortens prior to a blocked p-wave
Management
- symptomatic patients
- atropine 0.5-2.0 mg IV
- transcutaneous pacemaker in patients resistent to atropine
- bradycardia refractory to atropine & transcutaneous pacemaker not available
- dopamine 5-20 ug/kg/min
- epinephrine 2-20 ug/min
- isoproterenol 2-10 ug/min
- treat underlying disorder (i.e. acute coronary syndrome)[3]
More general terms
Additional terms
References
- ↑ Manual of Medical Therapeutics, 28th ed, Ewald & McKenzie (eds), Little, Brown & Co, Boston, 1995, pg 139
- ↑ Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 271
- ↑ 3.0 3.1 Medical Knowledge Self Assessment Program (MKSAP) 14, 17 American College of Physicians, Philadelphia 2006, 2015