How to manage a patient with symptomatic absolute bradycardia (abnormally slow heart rate)?

From the Guidelines

For a patient with absolute bradycardia, immediate treatment with atropine 0.5 mg IV is recommended, which can be repeated every 3-5 minutes up to a maximum of 3 mg, as it is the first-line drug for acute symptomatic bradycardia, according to the 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care 1. This approach is also supported by the 2010 international consensus on cardiopulmonary resuscitation and emergency cardiovascular care science with treatment recommendations, which suggests atropine 0.5 to 1 mg IV repeated every 3 to 5 minutes as needed up to 1.5 to 3 mg total as the first-line drug treatment for symptomatic bradycardia 1.

Key Considerations

• Assess if the patient is symptomatic, experiencing dizziness, syncope, hypotension, chest pain, or altered mental status, as this will guide the urgency of treatment.
• If atropine is ineffective, consider initiating transcutaneous pacing or administering dopamine (2-10 mcg/kg/min) or epinephrine (2-10 mcg/min) infusion.
• For asymptomatic patients with heart rate below 40 bpm or those with concerning features, close monitoring is essential to promptly identify any deterioration.
• Identify and treat underlying causes such as medications (beta-blockers, calcium channel blockers), electrolyte abnormalities, hypothyroidism, increased vagal tone, or cardiac ischemia, and discontinue or adjust rate-limiting medications if possible.

Important Notes

• Atropine should be used cautiously in the presence of acute coronary ischemia or MI, as increased heart rate may worsen ischemia or increase infarction size 1.
• The recommended atropine dose for bradycardia is 0.5 mg IV every 3 to 5 minutes to a maximum total dose of 3 mg, with doses of atropine sulfate of <0.5 mg potentially resulting in further slowing of the heart rate 1.

From the FDA Drug Label

Atropine-induced parasympathetic inhibition may be preceded by a transient phase of stimulation, especially on the heart where small doses first slow the rate before characteristic tachycardia develops due to paralysis of vagal control Adequate doses of atropine abolish various types of reflex vagal cardiac slowing or asystole The drug also prevents or abolishes bradycardia or asystole produced by injection of choline esters, anticholinesterase agents or other parasympathomimetic drugs, and cardiac arrest produced by stimulation of the vagus.

For a patient with absolute bradycardia, atropine can be used to abolish bradycardia by paralyzing vagal control and increasing the heart rate.

• Key consideration: Administer atropine with caution, as it may cause a transient phase of stimulation before the desired effect.
• Dosage: Not specified in the provided text, but should be determined based on the patient's condition and medical history. 2

From the Research

Management of Absolute Bradycardia

• The management of absolute bradycardia involves various strategies, including the use of atropine, transcutaneous cardiac pacing (TCP), and permanent pacemaker (PPM) implantation 3, 4, 5.
• Atropine is often recommended as a first-line therapy for unstable bradycardic patients, but its administration can sometimes lead to paradoxical worsening of bradycardia, particularly in patients with atrioventricular blocks at the level of the His-Purkinje fibers (infranodal) 3.
• Transcutaneous cardiac pacing (TCP) is a rapid, time-saving, and non-invasive ventricular stimulation that can be effective in treating symptomatic bradycardias, especially in patients who are unresponsive to atropine 4.
• The efficacy of TCP in unstable bradycardia patients has been demonstrated in several studies, with significant improvements in mean systolic and diastolic blood pressure, as well as median heart rate 4.

Considerations for Treatment

• The choice of treatment for absolute bradycardia depends on various factors, including the underlying cause of the bradycardia, the patient's clinical presentation, and the availability of resources 5.
• Permanent pacemaker (PPM) implantation may be considered for patients with irreversible causes of symptomatic bradycardia, such as heart block or atrial arrhythmias with slow ventricular response 5.
• The timing of PPM implantation is crucial, with early implantation (≤2 days) potentially reducing the risk of adverse events and shortening the length of stay 5.
• Prehospital transcutaneous cardiac pacing for symptomatic bradycardia or bradyasystolic cardiac arrest has been studied, but the evidence is limited, and its efficacy is still uncertain 6, 7.

Clinical Outcomes

• Clinical outcomes of various management strategies for symptomatic bradycardia have been evaluated in several studies, with findings suggesting that early intervention and appropriate treatment can improve patient outcomes 5.
• Adverse events related to bradycardia, such as syncope, central line-associated bloodstream infections, cardiac arrest, and in-hospital mortality, can be reduced with timely and effective treatment 5.
• The use of TCP and PPM implantation can be effective in managing symptomatic bradycardia, but the choice of treatment should be individualized based on the patient's specific needs and clinical presentation 3, 4, 5.