spectrum comparison
Heart Block Progression: First Degree → Second Degree Type I → Type II → Third Degree
The NCLEX gives you a rhythm strip and expects you to match it to the correct intervention in seconds. First degree needs nothing; third degree needs a pacemaker. The danger zone is confusing Type I (watch and wait) with Type II (prepare for pacing) — that mistake costs the patient their rhythm.
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Progression4 stages
Progression — 4 stages
1st Degree
What's happening- Slowed AV conduction
- Every P wave conducts
Key findings- PR > 0.20 sec, long but constant
- No dropped QRS
- Usually benign
Nursing focus- Monitor; usually no treatment
- Review AV-nodal blocking drugs
Wenckebach (Type I)
What's happening- Progressive AV delay until a drop
Key findings- ★PR lengthens then drops a QRS
- Grouped beats
- Usually narrow QRS
- Usually benign
Nursing focus- Monitor; usually no treatment
- Review AV-nodal blocking drugs
- Atropine if symptomatic
Mobitz II (Type II)
What's happening- Block below AV node (infranodal)
- Sudden dropped beats
Key findings- ★Constant PR, sudden dropped QRS
- Often wide QRS (BBB)
- Fixed P:QRS ratio (2:1, 3:1)
Nursing focus- Prepare transcutaneous pacing
- Atropine often ineffective
- Dopamine or epi infusion
Escalate when- Needs permanent pacemaker
- Can progress to 3rd degree
3rd Degree (Complete)
What's happening- Complete AV dissociation
Key findings- ★P waves & QRS march independently
- Slow escape rhythm, often < 40 bpm
Nursing focus- Prepare transcutaneous pacing
- Atropine often ineffective
- Dopamine or epi infusion
Escalate when- Needs permanent pacemaker
- Highest risk: asystole, syncope
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Clinical Pearl
Longer-longer-drop = Wenckebach (watch). Sudden drop, constant PR = Mobitz II (pace). No relationship = complete (emergency).
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