What are the diagnosis, causes, and management of junctional rhythm bradycardia (abnormally slow heart rate originating from the atrioventricular (AV) junction)?

From the Guidelines

Junctional rhythm bradycardia should be managed by addressing the underlying cause and considering permanent pacemaker implantation in symptomatic patients with hemodynamic compromise, as recommended by the 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay 1. Junctional rhythm bradycardia is a slow heart rhythm that originates from the atrioventricular (AV) junction when the sinoatrial (SA) node fails to function properly. It's diagnosed on ECG by the absence of P waves before QRS complexes, or by inverted P waves that appear after the QRS complex or hidden within it, along with a regular, narrow QRS complex. Common causes include:

• Medication side effects (beta-blockers, calcium channel blockers, digoxin)
• Increased vagal tone
• Ischemic heart disease
• Electrolyte abnormalities (particularly hyperkalemia)
• Hypothyroidism
• Degenerative conduction system disease Management depends on whether the patient is symptomatic. For asymptomatic patients, addressing the underlying cause may be sufficient. However, for symptomatic patients with hemodynamic compromise, immediate treatment includes:
• Atropine 0.5mg IV every 3-5 minutes up to a maximum of 3mg
• Temporary transcutaneous pacing should be initiated while preparing for transvenous pacing if atropine is ineffective
• Dopamine (2-10 mcg/kg/min) or epinephrine (2-10 mcg/min) infusions can be used as bridge therapies Long-term management may require permanent pacemaker implantation, especially in cases of degenerative conduction system disease, as stated in the guideline 1. The underlying mechanism involves failure of the SA node, causing the AV junction to take over as the heart's pacemaker at a slower intrinsic rate, which can lead to decreased cardiac output and symptoms like dizziness, fatigue, syncope, or even shock in severe cases. Establishing temporal correlation between symptoms and bradycardia is important when determining whether permanent pacing is needed, as emphasized in the guideline 1.

From the Research

Junctional Rhythm Bradycardia Overview

• Junctional rhythm bradycardia is a type of bradycardia that originates from the atrioventricular (AV) junction, which includes the AV node and the bundle of His.
• This condition can be caused by various factors, including:
  • Renal failure, which can lead to hyperkalemia and accumulation of toxins that affect the heart rate 2
  • Use of AV nodal blockers, such as beta blockers, which can slow down the heart rate 2
  • Hyperkalemia, which can affect the heart's electrical activity and lead to bradycardia 2

Diagnosis

• Diagnosis of junctional rhythm bradycardia typically involves:
  • Electrocardiogram (ECG) to evaluate the heart's electrical activity and confirm the presence of bradycardia
  • Laboratory tests to check for underlying conditions, such as renal failure and hyperkalemia
  • Physical examination to assess for signs of hemodynamic instability, such as hypotension and syncope

Management

• Management of junctional rhythm bradycardia depends on the underlying cause and the presence of hemodynamic instability.
• Treatment may involve:
  • Atropine, ionotropic, and vasopressive infusions to increase heart rate and blood pressure 2
  • Correction of underlying conditions, such as renal failure and hyperkalemia
  • Avoidance of AV nodal blockers, such as beta blockers, in patients with bradycardia
  • Mechanical pacing, if necessary, to maintain a stable heart rate 2
• It is essential to consider the multiple causes of bradycardia and tailor treatment to the individual patient's needs, rather than following a standard algorithm 2