ABCs
- ABCs and full vitals
- Recheck HR and confirm with ECG
- Hypoxemia is a common trigger correct immediately
- Place on cardiac monitor and prepare pacing pads
- Rule out monitor artifacts (e.g., cold hands, poor probe contact, motion)
HPI
- Symptoms -> lightheadedness, syncope, chest pain
- Signs of unstable bradycardia
- Altered mental status
- Ischemic chest pain
- Acute heart failure
- Hypotension
- Shock despite airway and oxygenation
Causes
| Intrinsic Causes | Extrinsic Causes |
|---|---|
| Idiopathic degeneration | Medications: |
| Ischemic heart disease | – Beta-blockers |
| Hypertensive heart disease | – CCBs (verapamil, diltiazem) |
| Cardiomyopathy | – Amiodarone, sotalol |
| Post-surgical / transplant-related | – Digoxin |
| Inflammatory / Infectious: | – Clonidine, methyldopa |
| – Pericarditis | – Lithium, antipsychotics, TCAs |
| – Myocarditis | Vasovagal syncope |
| – Rheumatic fever | Carotid sinus hypersensitivity |
| – Lyme disease | Hypothyroidism |
| Collagen vascular disease | Raised ICP |
| Trauma | Hypothermia |
| Neuromuscular / Genetic: | Hyperkalemia |
| – Friedreich ataxia | Hypoxia |
| – Muscular dystrophy | Anorexia nervosa |
| – Familial disorders |
workup
- Review meds -> beta-blockers, digoxin, CCBs, opioids, psych meds
- Labs -> Electrolytes, TSH, cardiac enzymes
- Consider imaging if neuro cause suspected
- ECG -> rhythm and blocks
| Rhythm | Features |
|---|---|
| Sinus bradycardia | Common in athletes, sleep, ↑ vagal tone |
| 1° AV block | PR > 200 ms |
| 2° AV block Type I (Wenckebach) | Progressive PR lengthening → dropped beat |
| 2° AV block Type II | Dropped beat with constant PR → high risk |
| 3° AV block | Atrial and ventricular dissociation → pacing often needed |
- High-Risk Features in AV Block
- Pause > 3 sec with symptoms
- Ventricular escape rhythm < 40 bpm
- Syncope + documented bradyarrhythmia
- Alternating bundle branch block
management
- If stable/asymptomatic + HR > 50 with no ECG changes
- Monitor and treat reversible causes:
- Hypoxia
- Hyperkalemia
- ACS
- Drug toxicity (beta blockers, CCBs, digoxin)
- Monitor and treat reversible causes:
- If unstable or symptomatic
- Call for assistance
- Give Atropine IV: 0.5–1 mg every 3–5 min (max 3 mg)
- Not effective in heart transplant or Mobitz II/3rd-degree AV block
- Escalate to temporary pacing as needed
- Call cardiology for pacing and further evaluation
🔗 Related External Links
Studying for R1? The IM Rapid Review covers this in the same format — see the sample chapter.
Last reviewed · May 2026