How do you manage symptomatic bradycardia?

Management of Symptomatic Bradycardia

For symptomatic bradycardia causing acute altered mental status, ischemic chest discomfort, acute heart failure, hypotension, or other signs of shock, administer atropine 0.5-1 mg IV immediately as first-line therapy, and prepare for transcutaneous pacing if atropine fails. 1

Initial Assessment and Stabilization

When a patient presents with bradycardia (heart rate <50 bpm), immediately assess whether the bradycardia is causing the symptoms:

• Evaluate for signs of poor perfusion: acute altered mental status, ischemic chest discomfort, acute heart failure, hypotension (systolic BP <90 mmHg), or other signs of shock 1, 2
• Maintain patent airway and assist breathing as necessary 1
• Provide supplementary oxygen if hypoxemic or showing increased work of breathing (tachypnea, intercostal retractions, suprasternal retractions) 1
• Establish IV access and attach cardiac monitor 1
• Obtain 12-lead ECG to define the rhythm, but don't delay therapy 1

Critical Distinction: Who Needs Treatment

Treat only if bradycardia is causing symptoms. The following patients do NOT require treatment:

• Asymptomatic patients with sinus bradycardia, even with rates <40 bpm 1
• Well-conditioned athletes with physiologic bradycardia 1
• Sleep-related bradycardia or pauses during sleep 1
• Patients whose symptoms occur in the absence of documented bradycardia 1

Pharmacologic Management Algorithm

First-Line: Atropine

Atropine remains the first-line drug for acute symptomatic bradycardia (Class IIa, Level of Evidence B) 1:

• Dose: 0.5-1 mg IV bolus 1, 3
• Mechanism: Reverses cholinergic-mediated decreases in heart rate by antagonizing muscarinic receptors 3
• Effective for: Symptomatic sinus bradycardia and conduction block at the AV node level 1
• Onset: Effects on heart rate are delayed by 7-8 minutes after IV administration 3

Common pitfall: Atropine may be less effective or ineffective for high-degree AV blocks (Mobitz type II, third-degree block) where the block is below the AV node in the His-Purkinje system 1

Second-Line: Chronotropic Agents

If bradycardia is unresponsive to atropine, initiate IV infusion of β-adrenergic agonists (Class IIa, Level of Evidence B) 1:

• Dopamine infusion: 5-20 mcg/kg/min, particularly useful if hypotension is present 1
• Epinephrine infusion: 2-10 mcg/min 1

These agents are especially appropriate when atropine is inappropriate or has failed 1

Pacing Strategies

Transcutaneous Pacing (TCP)

Initiate TCP in unstable patients who do not respond to atropine (Class IIa, Level of Evidence B) 1:

• TCP is effective as a temporizing measure while preparing for definitive therapy 1
• Consider immediate pacing in unstable patients with high-degree AV block when IV access is not available (Class IIb, Level of Evidence C) 1

Temporary Transvenous Pacing

Avoid routine use of temporary transvenous pacing when possible due to high complication rates (14-40% in studies, including central line-associated bloodstream infections) 1, 4, 5:

• Reserve for patients who fail TCP and pharmacologic therapy 1
• Not recommended for mildly to moderately symptomatic patients with intermittent episodes not associated with hemodynamic compromise 1
• Studies show temporary transvenous pacing is associated with significantly higher adverse events (19.1% vs 3.4%, P<.001) compared to other management strategies 5

Permanent Pacemaker Implantation

Permanent pacing is the only definitive therapy for persistent symptomatic bradycardia 6:

• Early PPM implantation (≤2 days) has similar adverse event rates compared to delayed implantation (6.6% vs 12.5%, P=.20) 5
• Weekend admissions delay PPM implantation by 1 day and prolong length of stay by 2 days; consider weekend implantation to avoid temporary transvenous pacing 5
• Approximately 50% of patients presenting with compromising bradycardia ultimately require permanent pacing 4

Identify and Treat Reversible Causes

Before considering permanent pacing, aggressively evaluate for reversible causes (Class I, Level of Evidence C-EO) 1:

• Medications: Beta-blockers, calcium channel blockers, digoxin, antiarrhythmic drugs—consider dose reduction or discontinuation 1
• Metabolic: Hypothyroidism, hyperkalemia, hypokalemia, severe acidosis 1
• Cardiac: Acute myocardial infarction (14% of cases), elevated intracranial pressure 1, 4
• Other: Drug intoxication (6% of cases), sleep apnea 4

In one registry, 21% of compromising bradycardia cases were due to adverse drug effects, and 39% of patients required only bed rest for symptom resolution 4

Special Considerations by Rhythm

Mobitz Type II Second-Degree AV Block

• High risk of progression to complete heart block, especially in setting of acute MI 1
• May require treatment even if minimally symptomatic due to risk of progression 1
• Atropine often ineffective as block is below AV node 1

Third-Degree (Complete) AV Block

• No impulses pass between atria and ventricles 1
• Can be permanent or transient depending on underlying cause 1
• Typically requires pacing if symptomatic 1

Bradycardic Atrial Fibrillation

• Accounts for 14% of compromising bradycardia presentations 4
• Evaluate for medication toxicity (especially digoxin) and thyroid dysfunction 4

Prognosis and Outcomes

• 30-day mortality: Approximately 5% in patients presenting with compromising bradycardia 4
• Need for temporary pacing: About 20% of patients with compromising bradycardia require temporary emergency pacing for initial stabilization 4
• Complications of PPM implantation: Range from 3-7% with significant long-term implications for transvenous lead systems 1