What is the management approach for bradycardia (abnormally slow heart rate)?

Management of Bradycardia

For symptomatic bradycardia with hemodynamic compromise, immediately administer atropine 0.5-1 mg IV as first-line therapy, repeating every 3-5 minutes up to 3 mg total, while simultaneously preparing for transcutaneous pacing if atropine fails. 1, 2

Initial Assessment and Stabilization

Determine if the bradycardia is causing the symptoms or if symptoms are from another condition causing bradycardia as a physiologic response. 1 This distinction is critical because treatment is only indicated when bradycardia directly causes:

• Hypotension (systolic BP <90 mmHg) 3
• Altered mental status or confusion 3
• Ischemic chest pain or angina 3
• Acute heart failure signs (pulmonary edema, dyspnea) 3
• Syncope or presyncope 3
• Shock with end-organ hypoperfusion 3

Establish IV access, continuous cardiac monitoring, and obtain a 12-lead ECG immediately, but do not delay treatment for ECG acquisition. 1 The ECG identifies the specific mechanism (sinus node dysfunction vs. AV block) which guides definitive management. 1

Identify and Treat Reversible Causes First

Before any intervention, aggressively evaluate for reversible causes—this is a Class I recommendation from the ACC/AHA. 4, 1 Permanent pacing should never be considered until reversible causes are excluded. 4

Common Reversible Causes:

• Medications: Beta-blockers, non-dihydropyridine calcium channel blockers (diltiazem, verapamil), digoxin, antiarrhythmics 1

  • Discontinue or reduce dosage of non-essential negative chronotropic drugs 4

• Metabolic/Endocrine: Hypothyroidism, hyperkalemia, hypokalemia, hypoglycemia, severe acidosis 1

• Cardiac: Acute myocardial infarction, cardiac surgery, elevated intracranial pressure 4

• Sleep apnea: Nocturnal bradycardia should prompt screening for sleep apnea, but is NOT an indication for permanent pacing 4

Acute Pharmacologic Management

First-Line: Atropine

Atropine 0.5-1 mg IV bolus is the first-line agent (Class IIa recommendation from AHA). 4, 1, 2

• Repeat every 3-5 minutes to maximum total dose of 3 mg 1, 2
• Do not use doses <0.5 mg as this may paradoxically slow heart rate 3
• Most effective for sinus bradycardia and AV nodal blocks 3
• Less effective for infranodal blocks (wide-complex escape rhythms) 3
• Contraindication: Avoid in heart transplant patients—causes paradoxical heart block or sinus arrest in 20% of cases 4

Second-Line: Beta-Adrenergic Agonists

If atropine fails or is contraindicated, consider: 1

• Dopamine infusion (5-20 mcg/kg/min, titrated every 2 minutes) 4
• Epinephrine infusion (2-10 mcg/min) 1
• Isoproterenol (1-20 mcg/min)—avoid in suspected coronary ischemia as it increases myocardial oxygen demand while decreasing coronary perfusion 4

Special Situations: Beta-Blocker/Calcium Channel Blocker Overdose

For symptomatic bradycardia from overdose (Class IIa recommendations): 4

• Calcium chloride or calcium gluconate IV for calcium channel blocker toxicity 4
• Glucagon for beta-blocker or calcium channel blocker toxicity 4
• High-dose insulin therapy for either toxicity 4

Temporary Pacing

Transcutaneous pacing is reasonable for symptomatic bradycardia unresponsive to atropine (Class IIa recommendation). 1, 3 Use as a bridge to transvenous or permanent pacing. 1 Note that transcutaneous pacing is painful and less reliable than transvenous pacing. 1

Temporary transvenous pacing is indicated for hemodynamically compromising bradycardia refractory to medical therapy. 1 This provides more stable pacing than transcutaneous methods while definitive management is arranged. 5

Indications for Permanent Pacemaker

Class I Indications (Must Pace):

Permanent pacing is mandatory for second-degree Mobitz type II, high-grade AV block, or third-degree AV block NOT caused by reversible causes—regardless of symptoms. 4, 1 These conditions carry risk of progression to asystole. 4

Permanent pacing is indicated for symptomatic bradycardia that persists after excluding and treating all reversible causes. 4, 1, 3

Permanent pacing is required when symptomatic bradycardia develops as a consequence of guideline-directed medical therapy (e.g., beta-blockers for heart failure) for which there is no alternative treatment and continued therapy is clinically necessary. 4

Class IIa Indication:

For tachy-brady syndrome with symptoms attributable to bradycardia, permanent pacing is reasonable. 4 These patients often require both pacemaker therapy and antiarrhythmic drugs. 4

When NOT to Pace:

Asymptomatic or minimally symptomatic patients have NO indication for permanent pacing, even with documented bradycardia on monitoring or electrophysiology studies. 4 There is no established minimum heart rate or pause duration that mandates pacing in sinus node dysfunction. 4

Nocturnal bradycardia alone is NOT an indication for permanent pacing. 4 Screen for sleep apnea instead, as treatment of sleep apnea reduces bradycardia frequency. 4

Special Pacing Considerations

In patients with LVEF 36-50% and AV block requiring pacing >40% of the time, use cardiac resynchronization therapy or His bundle pacing rather than standard right ventricular pacing to prevent heart failure. 4 This is critical to avoid pacing-induced cardiomyopathy.

Key Clinical Pitfalls

• Do not confuse physiologic bradycardia with pathologic bradycardia. Asymptomatic sinus bradycardia (even 40-45 bpm) is common in athletes, during sleep, and in young healthy individuals—no treatment needed. 3

• Correlation between symptoms and documented bradycardia is essential. 4 If symptoms occur without bradycardia on monitoring, pacing provides no benefit. 4

• First-degree AV block is benign and requires no treatment. 3

• Age alone is not a contraindication to pacing, but goals of care discussions considering functional status, life expectancy, and quality of life priorities are essential in elderly patients. 3

• Left bundle branch block on ECG markedly increases likelihood of structural heart disease—obtain echocardiography. 4