Management of bradycardia

Bradycardia is generally defined as a heart rate of < 60/min. All patients require urgent evaluation with ECG and monitoring. Patients with unstable bradycardia require immediate stabilization, initially with IV atropine, followed by transcutaneous pacing and/or IV chronotropic medications (e.g., dopamine, epinephrine), and transvenous pacing for refractory bradycardia. Treatment should also address reversible underlying causes of bradycardia, e.g., hypoxemia, acute coronary syndrome, electrolyte disturbances, and medication-induced bradycardia. Stable patients may not require immediate intervention, but often require monitoring and investigations to determine the underlying etiology and risk of progression to unstable bradycardia or sudden cardiac death. Definitive management depends on the underlying cause of bradycardia and can include permanent pacemaker implantation for patients with nonreversible bradyarrhythmias.

See also “Overview of cardiac arrhythmias,” “Sinus node dysfunction,” “Atrioventricular block,” and “Cardiac implantable electronic devices.”

Approach ^[1][2]

• Follow ABCDE approach and check pulse.
  • Pulseless patients: Start CPR (see “ACLS”).
  • Pulse present: Evaluate hemodynamic stability.
• Clinical features of unstable bradycardia present: Follow adult unstable bradycardia algorithm.
• Stable bradycardia: Manage according to underlying etiology and symptom severity.
  • Evaluate for symptoms attributable to bradyarrhythmia.
  • Identify ECG abnormality: e.g., sinus node dysfunction (SND), atrioventricular block (AV block), or conduction disorders (e.g., LBBB, RBBB).
  • Uncertain diagnosis: Consider additional diagnostics (e.g., TTE) on an individual basis.
  • Identify indications for permanent pacemaker insertion.

Patients with unstable bradycardia need immediate stabilization with IV atropine, temporary cardiac pacing, and/or IV chronotropic medication, e.g., dopamine or epinephrine. ^[1]

Patients asymptomatic stable bradycardia or only mildly symptomatic stable bradycardia typically do not require acute intervention. ^[2]

Initial management of bradycardia

• Call for help.
• Establish IV access.
• Bring crash cart to bedside and attach pads.
• Begin continuous cardiac and respiratory monitoring.
• Unstable bradycardia: Begin stabilization according to the adult unstable bradycardia algorithm.
• Evaluate underlying rhythm.
  • Unstable patients: Obtain rhythm strip first.
  • All patients: Obtain 12-lead ECG.
• Identify and treat reversible causes of bradycardia, e.g., supplemental O₂ for hypoxemia. ^[2][3]
• Consult cardiology.

Do not delay acute stabilization of unstable bradycardia to obtain a 12-lead ECG for rhythm identification.

Overview of bradyarrhythmias

Clinical features of unstable bradycardia ^[1]

• Acute altered mental status
• Ischemic chest pain
• Acute heart failure
• Hypotension
• Signs of shock despite adequate airway and breathing

Adult unstable bradycardia algorithm ^[1][2]

Start initial management of bradycardia and immediate hemodynamic support simultaneously with the following treatment:

• First-line: IV atropine
• If refractory to atropine: Start temporizing measures.
  • Transcutaneous pacing
  • AND/OR IV pharmacotherapy
    • Dopamine
    • OR Epinephrine
• If refractory to pharmacotherapy: Consult cardiology for transvenous pacing.

Concurrently treat reversible causes of bradycardia, e.g., hypoxia, hyperkalemia, acute coronary syndrome, beta blocker toxicity, CCB toxicity, cardiac glycoside toxicity.

Special situations ^[2]

• No IV access or IO access: Consider transcutaneous pacing as first-line intervention while awaiting vascular access. ^[1]
• Acute coronary syndrome
  • Use atropine with caution.
  • Temporary pacing is indicated for unstable bradycardia.
  • If MI is causing AV block: Consider aminophylline ^[2]
• Recent heart transplant
  • Atropine is contraindicated.
  • Consider alternative chronotropic medications
    • Aminophylline ^[2]
    • OR Theophylline ^[2]
• Known infranodal block or a wide QRS with AV block: Consider transcutaneous pacing as first-line intervention instead of atropine. ^[2][3]
• Spinal cord injury: Consider alternative chronotropic medications if unresponsive to atropine and inotropes.
  • Aminophylline ^[2]
  • OR Theophylline ^[2]

Management

• Begin definitive therapy for specific bradyarrhythmias under specialist guidance.
  • See “Management of high-risk AV block.”
  • See “SND treatment.”
• Identify indications for permanent pacemaker insertion.
• Continue treatment of the underlying cause of bradycardia.

Disposition

• Inpatient cardiology consult for all patients
• Urgent cardiology consult if transvenous pacing is required
• ICU or CCU admission

• ABCDE survey
• IV access, continuous telemetry, and pulse oximetry
• Unstable and/or symptomatic bradycardia: Administer atropine.
• If atropine is ineffective, consider temporizing measures (tailored to the patient).
  • Transcutaneous pacing
  • AND/OR pharmacotherapy
    • Dopamine
    • OR Epinephrine
• Consult cardiology.
• Consider transvenous pacing.
• Identify and treat the underlying cause of bradycardia.
• Admit to the ICU.

Provide initial management of bradycardia concurrently for all patients.

If signs of unstable bradycardia develop at any time, follow the adult unstable bradycardia algorithm.

Diagnostics ^[2]

• Conduct comprehensive clinical evaluation and obtain 12-lead ECG in all patients.
• Consider additional diagnostics on an individual basis under specialist guidance.
  • Obtain TTE if ECG is nondiagnostic and structural heart disease is suspected.
  • Consider exercise ECG testing for exertional symptoms.
  • Consider ambulatory ECG monitoring for intermittent symptoms. ^[2]

Management

• Asymptomatic or only mildly symptomatic patients typically do not require acute intervention.
• Definitive management depends on the underlying rhythm.
  • See “SND treatment.”
  • See “Management of low-risk AV block.”
  • See “Management of high-risk AV block.”

High-risk AV block is an indication for permanent pacemaker insertion.

Disposition ^[2]

Consult cardiology as disposition varies depending on underlying rhythm and etiology, symptom severity, and patient factors.

• Symptomatic stable bradycardia
  • Inpatient cardiology consult is typically required.
  • Most patients require admission with continuous cardiac monitoring.
• Asymptomatic stable bradycardia
  • Patients may require observation.
  • Consider outpatient cardiology evaluation and follow-up for low-risk patients.

Transcutaneous pacing ^[4][5]

• Definition: a temporizing treatment for bradyarrhythmias in which electrical impulses are delivered through pacing pads placed on the chest wall to stimulate cardiac contraction
• Indication: unstable bradycardia for which pharmacotherapy alone either is ineffective, not readily available, or contraindicated
• Contraindications: no absolute contraindications

Technical background

• Pacemaker spike: A narrow upward deflection on an ECG tracing caused by an electrical impulse from a pacemaker.
• Electrical capture
  • Successful conduction of current from an external pacemaker to the conduction system of the heart
  • Manifests on ECG as a pacer spike immediately followed by a widened QRS complex.
• Mechanical capture
  • Physical cardiac contraction that occurs when current is conducted from an external pacemaker
  • Manifests as a palpable pulse, a pulse oximetry waveform, or ventricular contraction visible on POCUS.

Equipment

• Pacer pads
• Transcutaneous pacemaker
• Continuous cardiac monitoring
• Pulse oximetry
• Bedside ultrasound (optional)

Landmarks and positioning

• Anterior-lateral pacer pad placement
  • Anterior pad inferior to the right clavicle
  • Lateral pad over the left 5th–6th intercostal space on the anterior axillary or midaxillary line
• Anterior-posterior pacer pad placement
  • Anterior pad on the sternum
  • Posterior pad on the left infrascapular region

Consider placing pacer pads early in patients with bradyarrhythmias at risk of decompensation. ^[4]

Procedure ^[4]

1. Apply pacer pads to the chest.
2. Connect the cable from the pads to the pacemaker.
3. Turn on the pacemaker and select the pacer function.
4. Verify that the pacemaker detects the patient's intrinsic rhythm.
5. Set the pacing rate higher than the patient's native heart rate (generally 60–70/minute).
6. Increase the current output until electrical capture occurs. ^[6]
7. Confirm mechanical capture clinically or using POCUS.
8. Maintain the current 5–10 mA above the minimum current required for mechanical capture. ^[6][7]
9. Provide procedural sedation for conscious patients, unless there is persistent hemodynamic instability.

In the unconscious or near-arrest patient, start the current at maximum and decrease until capture is lost. Maintain the final output at 5–10 mA above this threshold. ^[5]

Postprocedural care ^[5]

• Optimize procedural sedation and analgesia, preferably with hemodynamically neutral agents for PSA (e.g., etomidate, ketamine). ^[8]
• Consult cardiology for definitive management.

Troubleshooting

Consider the following if electrical capture or mechanical capture is lost:

• Reposition pacer pads.
• Improve skin-pad contact.
• Minimize chest impedance.
• Manage systemic conditions (e.g., myocardial ischemia, acidosis, hypoxia).

Complications ^[4][6]

• Pain
• Skin burns
• Loss of electrical capture and/or mechanical capture
• Tachyarrhythmias (e.g., ventricular fibrillation)
• Cough and/or hiccups
• Pacemaker syndrome

Transvenous pacing ^[4]

• Definition: The delivery of electrical impulses to stimulate cardiac contraction using an electrode placed via a central venous access site into the right ventricle; often used as a bridge to permanent pacemaker implantation
• Indications ^[4]
  • Symptomatic sinus node dysfunction
  • Second-degree or third-degree heart block
  • Afib with SVR
  • CIED malfunction
  • Also used for temporary antitachycardia pacing
• Contraindications: prosthetic tricuspid valve, severe hypothermia
• Complications: Usually related to vascular access (see “Complications” in “Central venous access.”)

Acute management of reversible causes ^[2][3]

• Provide oxygen therapy and/or mechanical ventilation for hypoxemic respiratory failure.
• Identify and treat acute coronary syndrome.
• Check core temperature and provide rewarming therapy for hypothermia.
• Identify opioid toxidrome and treat opioid toxicity if needed.
• Screen for and treat medication-induced bradycardia.
• Obtain laboratory studies for metabolic causes (e.g., electrolytes, TSH) and treat urgent disturbances.
  • See “Acute management checklist for hyperkalemia.”
  • See “Acute management checklist for myxedema coma.”
• Treat permanent pacemaker malfunctions, if present.

Medication-induced bradycardia ^[2]

Identify medications that may cause bradycardia (e.g., beta blockers, CCBs, digoxin, antiarrhythmics).

Stable bradycardia

Management depends on the indication and individual patient risk. Consult the prescribing clinician if available.

• Noncritical medication: Consider temporary hold or permanent discontinuation.
• Critical medication: Consider dosage reduction or alternative agents under specialist guidance.

Unstable bradycardia

• Follow the adult unstable bradycardia algorithm.
• If indicated, consider adding antidotes for cardiovascular drug poisoning (e.g., CCB poisoning, beta blocker poisoning, digoxin poisoning), such as:
  • Calcium for drug poisoning
  • High-dose euglycemic insulin therapy
  • High-dose glucagon
  • Digoxin immune fab
  • Intravenous lipid emulsion therapy
  • Methylene blue for drug poisoning

Etiologies by underlying mechanism