Definition
• These occur when conduction from the atria to the AV node & into the His bundle is disrupted
• These blocks can anatomically be located above, w/i, or below the His bundle
• Classified as 1st-degree, 2nd-degree Mobitz I (Wenckeback), 2nd-degree Mobitz II, & 3rd-degree blocks based on characteristic ECG patterns:
Approach
• Differentiate 1st, 2nd Mobitz I (Wenckebach), 2nd Mobitz II, & 3rd-degree blocks
• 2° Mobitz II & 3° blocks are never nl → look for underlying cardiac dz
• In children, be highly suspicious of toxic ingestion
• In neonates, consider congenital cardiac dz
• Determine (1) rate, (2) wide or narrow QRS, (3) rhythm regular or irregular, (4) P waves present or absent, (5) every P wave followed by QRS & every QRS preceded by P
History
• 1°: Asymptomatic, incidental finding on ECG
• 2° Mobitz I (Wenckebach): Often asymptomatic; irregular heartbeat, fatigue
• 2° Mobitz II: May be asymptomatic; presyncope/syncope, fatigue, DOE
• 3° usually symptomatic; presyncope/syncope, fatigue, weakness, DOE
Findings
• See above
Evaluation
• ECG & rhythm strip
• 2° Mobitz II & 3°: Labs in anticipation of PPM placement
Treatment
• 1° & 2° Mobitz I: No tx generally necessary
• 2° Mobitz II & 3°:
• Continuous tele monitoring
• Symptomatic pts require transcutaneous &/or transvenous pacing; if HD unstable, consider a beta-adrenergic agent (dopamine, epinephrine, or isoproterenol) as bridge to pacing. Dopamine has been demonstrated to have equivalent survival outcomes & adverse events to transcutaneous pacing (PrePACE, Resuscitation 2008;76(3):341)
• Treat active cardiac ischemia
• Consult cardiology
Disposition
• Pts w/ 1° & 2° Mobitz I: D/c home w/ f/u
• Pts w/ 2° Mobitz II & 3°: Admit all to Tele ward for cardiology consult & PPM
Pearls
• Avoid atropine for reversal of AV block as this can worsen conduction
• Have transcutaneous pacer attached & ready for use in high-risk pts
• Mobitz II is concerning b/c risk of progression to 3°