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ClearRounds Health · Cardiology · Quick Reference
AV Block
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Arrhythmias & DevicesIntermediateIn progressOne-page PDF
First-degree, Mobitz I, Mobitz II, complete heart block, reversible causes, urgent referral, and pacing indications.
Covers first-degree through complete heart block.
Last reviewed
Pending initial clinical review
Sources / guidelines to verify
- 2018 ACC/AHA/HRS Bradycardia & Conduction Delay Guideline
Disclaimer: Educational reference only. Not a substitute for clinician judgment, local protocols, or current guideline review.
One-page reference
Draft content pending the site owner’s clinical review. Verify against the sources above and local protocol before clinical use.
1
What it is / why it matters
- Impaired AV conduction, ranging from benign first-degree to high-grade/complete block needing pacing.
- The key clinical question: is it nodal (often benign) or infranodal (dangerous)?
2
Key diagnostic clues
Types
- 1st-degree: PR >200 ms, all beats conducted — usually benign
- Mobitz I (Wenckebach): progressive PR lengthening then a dropped beat — usually nodal/benign
- Mobitz II: constant PR then a sudden dropped beat — infranodal, risk of progression
- 3rd-degree (complete): AV dissociation with an escape rhythm — needs pacing
3
Initial workup
- ECG/telemetry; BMP including K⁺/Mg²⁺; TSH; medication review (beta-blocker, CCB, digoxin).
- Evaluate for ischemia and reversible causes (Lyme, high vagal tone).
- Assess symptoms (syncope, fatigue).
4
Management framework
- Treat reversible causes: hold offending drugs, correct electrolytes, treat ischemia or Lyme.
- Symptomatic/unstable bradycardia: atropine, transcutaneous pacing, and isoproterenol/dopamine as a bridge.
- Permanent pacemaker for symptomatic Mobitz I, Mobitz II, high-grade, or complete heart block not due to a reversible cause.
5
Red flags / escalate now
- Syncope or hemodynamic instability.
- Mobitz II, complete heart block, wide escape rhythm, or alternating bundle branch block → urgent monitoring + cardiology/EP for pacing.
6
Follow-up / monitoring
- Telemetry until a decision is made; device follow-up after implant.
7
Clinic pearls
- Mobitz I is usually benign; Mobitz II is dangerous (infranodal) — refer.
- New AV block + chest pain → think ischemia.
- Always review rate-slowing medications and Lyme exposure before committing to a pacemaker.
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