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Post-Operative Bradycardia

Definition

Bradycardia = HR < 60 bpm, clinically significant when < 50 bpm or associated with symptoms.
Causes may be physiologic (vagal tone, athletic conditioning, sleep) or pathologic (ischemia, conduction disease, drugs, metabolic derangements).

  • Symptoms: syncope, presyncope, hypotension, dyspnea, chest pain, altered mental status.
  • Differentiate:
  • Sinus node dysfunction (pacing defect)
  • Atrioventricular [AV] block (conduction defect)

I. Principles

  • Not all bradycardia requires intervention — treat the patient, not the number.
  • Always exclude reversible causes first.
  • Use ACLS framework: Airway, Breathing, Circulation → Identify Rhythm → Intervene.
  • High-grade AV block or unstable bradycardia = emergent pacing.

II. Etiologies

Reversible / Transient

  • Vagal stimulation (pain, suctioning, intubation)
  • Medications: β-blockers, CCBs, digoxin, antiarrhythmics, anesthetics
  • Electrolyte derangements: K⁺, Mg²⁺, Ca²⁺
  • Hypothermia, hypothyroidism, sleep apnea

Pathologic

  • Ischemia (inferior MI)
  • Infection (endocarditis with abscess, sepsis)
  • Infiltrative/inflammatory: amyloidosis, sarcoidosis
  • Post-cardiac surgery: valve, CABG, congenital repair

III. AV Block Classification

  • First-degree: prolonged PR, 1:1 conduction
  • Mobitz I (Wenckebach): progressive PR lengthening, dropped QRS
  • Mobitz II: constant PR, intermittent dropped QRS — unstable, needs pacing
  • Third-degree (complete block): no atrial conduction, ventricular escape rhythm

IV. Evaluation

  1. Confirm rhythm: EKG, telemetry
  2. Assess hemodynamics: BP, mental status, O₂ sat, urine output
  3. Labs: electrolytes, troponin, thyroid function if indicated
  4. Echocardiogram if infiltrative/structural suspicion
  5. Ambulatory monitoring if recurrent outpatient symptoms

V. Management

A. Stable, Asymptomatic

  • Observation + continuous monitoring
  • Correct reversible causes
  • Avoid AV nodal blockers (β-blockers, CCBs, digoxin, adenosine)

B. Symptomatic or High-Grade Block (Mobitz II, Complete HB)

  • Call senior + cardiology/EP immediately
  • Treat reversible causes
  • Prepare for permanent pacemaker evaluation

C. Unstable (hypotension, AMS, ischemia, shock)

Follow ACLS 2025 algorithm:
1. Atropine 1 mg IV q3–5 min (max 3 mg)
- Avoid in heart transplant patients → go directly to pacing/pressors.
2. If ineffective:
- Transcutaneous pacing (TCP) (sedate if able)
- Dopamine infusion: 5–20 µg/kg/min
- Epinephrine infusion: 2–10 µg/min
3. If refractory:
- Transvenous pacing, CCU transfer, cardiology/EP consult

VI. ACLS Algorithm (ASCII Flowchart)

image

VII. Quick Reference: Drugs & Doses

Medication Dose / Route Notes / Cautions
Atropine 1 mg IV q3–5 min (max 3 mg) Avoid in heart transplant patients
Dopamine 5–20 µg/kg/min IV infusion Titrate to HR & BP; vasopressor effects
Epinephrine 2–10 µg/min IV infusion Potent; monitor closely for tachyarrhythmias
TCP Start at 60–80 bpm, sedation if time allows First-line if atropine ineffective
TVP Transvenous pacing Definitive bridge until permanent pacemaker

VIII. Red Flags – Call Senior Immediately

  • HR < 40 bpm sustained
  • Symptomatic bradycardia (syncope, hypotension, AMS, chest pain)
  • Mobitz II or Complete Heart Block
  • New bradycardia post-cardiac surgery
  • Bradycardia with sepsis or suspected perivalvular abscess

IX. Intern Pearls

  • Not all bradycardia needs treatment—asymptomatic and stable often safe to monitor.
  • Always review the med list for nodal blockers.
  • If unstable: Atropine → TCP/Pressors → TVP.
  • Pacemaker is definitive therapy for high-grade AV block.
  • Treat underlying causes in parallel, don’t delay.

X. References

  1. Kusumoto FM, et al. 2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Bradycardia and Cardiac Conduction Delay. JACC. 2019;74(7):e51–e156.
  2. American Heart Association. ACLS Bradycardia Algorithm. 2025 Provider Manual Updates & FAQs. cpr.heart.org.
  3. Neumar RW, et al. Part 8: Adult ACLS: Bradycardia with a Pulse. Circulation. 2015;132:S444–S464.
  4. Fulton MR II. Advanced Cardiac Life Support (ACLS). StatPearls. 2025.

Key Takeaways

  • Differentiate sinus bradycardia vs AV block.
  • Stable + asymptomatic → monitor and treat causes.
  • Symptomatic/high-grade AV block → urgent pacing, consider pacemaker.
  • Unstable bradycardia = ACLS algorithm: Atropine → TCP/Pressors → TVP.
  • Always search for reversible causes in parallel.