What is the Bezold-Jarisch reflex?

The Bezold-Jarisch Reflex

The Bezold-Jarisch reflex is a cardioinhibitory reflex originating from sensory receptors in the inferoposterior wall of the left ventricle, characterized by bradycardia, hypotension, and in some cases apnea, transmitted through unmyelinated vagal C fibers. 1

Pathophysiology and Mechanism

• The Bezold-Jarisch reflex is an inhibitory reflex with afferent pathways that transfer information from cardiac receptors to the brain via the vagus nerve 1, 2
• It originates specifically from mechanoreceptors located in the inferoposterior wall of the left ventricle 1, 2
• The reflex is transmitted through unmyelinated vagal C fibers, which carry the signal to the vasomotor centers in the brainstem 1
• When triggered, it causes a paradoxical withdrawal of sympathetic outflow, resulting in sudden decrease in blood pressure with bradycardia 1

Clinical Manifestations

• The classic triad of the Bezold-Jarisch reflex includes:
  • Bradycardia (often severe, with heart rates dropping significantly) 3, 4
  • Hypotension (can be profound, with systolic blood pressure dropping to dangerous levels) 3, 5
  • Apnea or bradypnea (decreased respiratory rate) 3, 2
• Unlike typical vasovagal syncope which usually presents with cutaneous manifestations, Bezold-Jarisch reflex may occur without skin changes 1

Clinical Contexts and Triggers

• The reflex can be triggered in various clinical scenarios:
  • During regional anesthesia, particularly in the sitting position during upper-extremity nerve blocks 5
  • In the setting of acute myocardial ischemia/infarction, especially inferior wall myocardial infarction 1
  • During neuraxial anesthesia, such as combined spinal-epidural procedures 3
  • In postoperative pediatric cardiac surgical patients 4
  • In the context of intradialytic hypotension (IDH) in hemodialysis patients 1

Differential Diagnosis

• The Bezold-Jarisch reflex should be distinguished from:
  • Vasovagal (vasodepressor) reactions, which typically include pallor, weakness, nausea, and diaphoresis 1
  • Orthostatic hypotension, which occurs within 3 minutes of standing 1
  • Cardiac syncope from other causes (arrhythmias, structural heart disease) 6
  • Anaphylaxis, which typically presents with cutaneous manifestations in >90% of cases 1

Clinical Significance

• In the context of myocardial ischemia, the Bezold-Jarisch reflex can be part of the pathophysiological mechanism of syncope 1
• During anesthesia procedures, this reflex can cause severe hemodynamic compromise requiring immediate intervention 3, 5
• In postoperative cardiac patients, particularly pediatric ones, it may present as cardiovascular collapse 4
• The reflex shows nonuniform responses in different sympathetic pathways - cardiac sympathetic nerve activity may be excited while lumbar sympathetic activity is inhibited 7

Management

• Immediate interventions for acute Bezold-Jarisch reflex include:

  • Atropine administration (0.01 mg/kg as bolus, followed by continuous infusion if needed) 4
  • Positioning (left lateral position in pregnant patients) 3
  • Intravenous fluid administration 3, 5
  • Judicious use of vasopressors in severe cases 3
  • Stopping the triggering stimulus if identifiable 5

• In the context of hemodialysis-related hypotension:

  • Medications like sertraline have shown benefit in improving hemodynamic parameters 1
  • Adjustments to dialysis protocols may help prevent activation of the reflex 1

Important Considerations

• The Bezold-Jarisch reflex can cause bradycardia during anaphylaxis, which might confuse the clinical picture since anaphylaxis typically presents with tachycardia 1
• The reflex can be particularly dangerous in certain clinical contexts like neuraxial anesthesia during cesarean section, affecting both mother and fetus 3
• Cardiac monitoring is essential in situations where this reflex might be triggered 5