When is pacing considered in the Emergency Department (ED) for patients with bradycardia or tachycardia?

Pacing in the Emergency Department

Indications for Transcutaneous Pacing in Bradycardia

Transcutaneous pacing (TCP) should be initiated in the ED for patients with symptomatic bradycardia who remain hemodynamically unstable despite atropine administration, particularly those with severe hypotension, altered mental status, or signs of shock. 1

Treatment Algorithm for Symptomatic Bradycardia

The approach follows a stepwise escalation based on response:

First-Line Pharmacologic Therapy:

• Administer atropine 0.5-1 mg IV bolus as initial treatment 1
• Repeat every 3-5 minutes up to maximum total dose of 3 mg 1
• Doses <0.5 mg should be avoided as they may paradoxically worsen bradycardia 1

Second-Line Options When Atropine Fails:

• Initiate TCP immediately for unstable patients (Class IIa recommendation) 2, 1
• Alternatively, start IV infusion of chronotropic agents: 1
  • Dopamine 5-10 mcg/kg/min IV
  • Epinephrine 2-10 mcg/min IV
  • Isoproterenol 2-10 mcg/min IV

Clinical Evidence Supporting TCP

Research demonstrates TCP is clinically effective in atropine-resistant unstable bradycardia, with significant improvements in systolic blood pressure (from 71 to 105 mmHg), diastolic blood pressure (from 43 to 61 mmHg), and heart rate (from 40 to 74 bpm) after first application 3. Importantly, TCP appears most beneficial in patients who maintain a palpable pulse on presentation, with 80% survival to hospital discharge in this subgroup compared to 0% without pacing 4.

Critical Predictors of TCP Effectiveness

TCP should be prioritized when:

• Patient has palpable pulse on arrival (strong predictor of benefit) 4
• Hemodynamic instability persists after maximum atropine dosing 1
• Type II second-degree or third-degree AV block with wide QRS is present (atropine likely ineffective) 1

TCP has limited utility when:

• Patient presents in asystole or pulseless bradycardia (no survivors in cardiac arrest scenarios) 5
• Cardiac arrest has already occurred 5

Rhythm-Specific Considerations

Atropine likely effective (may delay or avoid pacing):

• Sinus bradycardia 1
• AV nodal block 1
• Sinus arrest 1

Atropine likely ineffective (proceed directly to TCP/chronotropes):

• Type II second-degree AV block 1
• Third-degree AV block with wide QRS complex 1
• Post-cardiac transplant patients (atropine may cause paradoxical high-grade AV block) 1

Practical Implementation of TCP

Technical parameters:

• Most patients require 40-80 mA current for capture 6
• Higher thresholds expected in emphysema, pericardial effusion, or positive pressure ventilation 6
• Successful capture shows widened QRS complex followed by distinct ST segment and broad T wave 6

Essential confirmatory steps:

• Always verify mechanical capture by palpating arterial pulse, not just ECG capture 6
• Provide adequate sedation/analgesia as TCP is painful in conscious patients 1, 6

Common Pitfalls to Avoid

• Do not delay TCP while giving additional atropine doses in unstable patients 1
• Do not treat the heart rate number alone—treat the patient's clinical status 7
• Do not use TCP in asymptomatic bradycardia (Class III: Harm recommendation) 7
• Do not confuse "history of symptoms" with "currently symptomatic"—only intervene for current hemodynamic compromise 7

Real-World ED Data

In a 10-year registry of 277 patients presenting with compromising bradycardia, approximately 20% required temporary emergency pacing (transcutaneous or transvenous) for initial stabilization, while 39% stabilized with bed rest alone and 61% received IV chronotropic drugs 8. Ultimately, 50% required permanent pacemaker implantation 8.

Pacing Considerations for Tachycardia

Synchronized cardioversion, not pacing, is the appropriate intervention for unstable tachycardia in the ED. 2

Hemodynamically Unstable Tachycardia

• Immediate synchronized cardioversion is indicated for any tachycardia causing hemodynamic instability 2
• This includes atrial fibrillation with rapid ventricular response causing hypotension, altered mental status, or acute heart failure 2

Specific Tachycardia Scenarios Where Pacing May Be Considered

Torsades de pointes (polymorphic VT with long QT):

• Overdrive pacing may be effective when associated with bradycardia or pause-dependent episodes 2
• Pacing is adjunctive to IV magnesium and correction of underlying causes 2
• Consider pacing when polymorphic VT is precipitated by pauses in rhythm 2

Polymorphic VT with acquired long QT syndrome:

• Addition of pacing may be considered when accompanied by bradycardia 2
• Isoproterenol or ventricular pacing can terminate torsades associated with bradycardia and drug-induced QT prolongation 2

Critical Warning

Avoid isoproterenol in familial long QT syndrome—use pacing and β-blockers instead 2