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.

Comparison

Progression4 stages

Progression — 4 stages

First Degree
What's happening
- Slowed AV conduction; all beats conduct
Key findings
- PR > 0.20 sec, long but constant
- No dropped QRS; benign, often incidental
Nursing focus
- Document and monitor
- Watch AV-blocking drugs
→
2nd Degree Type I (Wenckebach)
What's happening
- Progressive AV delay until a drop
Key findings
- ★PR lengthens then drops a QRS
- Grouped beats; narrow QRS; usually benign
Nursing focus
- Observe; hold AV-blocking meds
- Atropine if symptomatic
→
2nd Degree Type II (Mobitz II)
What's happening
- Infranodal block; sudden dropped beats
Key findings
- ★Constant PR, sudden dropped QRS
- Wide QRS (BBB); fixed ratios (2:1, 3:1)
Nursing focus
- Prepare transcutaneous pacing
- Atropine often ineffective
Escalate when
- Pace now — temporary, permanent likely
→
Third Degree (Complete)
What's happening
- Complete AV dissociation
Key findings
- ★P waves & QRS march independently
- Ventricular rate 20–40 bpm
Nursing focus
- Transcutaneous pacing immediately
- Atropine bridge; dopamine/epi if no pacer
Escalate when
- Emergent pacing — terminal if untreated