What causes bradycardia in a female patient during hysteroscopy?

Bradycardia During Hysteroscopy

Bradycardia during hysteroscopy is primarily caused by vasovagal reflex—an inappropriate autonomic response triggered by cervical manipulation, uterine distension, and pain that results in parasympathetic activation and sympathetic withdrawal, leading to both bradycardia and vasodilation. 1, 2

Primary Mechanism: Vasovagal Reflex

The vasovagal response (also called the Bezold-Jarisch reflex) represents the most common cause of bradycardia during hysteroscopy. This occurs through:

• Parasympathetic activation combined with sympathetic inhibition, triggered by mechanical stimulation of the cervix and uterus during instrumentation 2
• Reduced cardiac venous return from patient positioning and procedural factors that paradoxically activate baroreceptors 2
• Affective mechanisms including pain and anxiety that further amplify the vagal response 2

The key distinguishing feature is that vagally-mediated bradycardia occurs with concomitant sinus node slowing (P-P prolongation) and typically resolves when the stimulus is removed 3, 4

Contributing Factors

Patient-Related Risk Factors

• Age >60-65 years increases susceptibility to bradycardia during procedures 5, 6
• Baseline heart rate <60 bpm predisposes to more severe bradycardia 5, 6
• Concurrent beta-blocker use or other negative chronotropic medications 5, 6
• ASA Class III-IV comorbidities 5, 6

Procedure-Related Triggers

• Cervical manipulation and dilation, particularly when using larger diameter hysteroscopes (≥5mm) 7
• Uterine distension from saline instillation, especially at higher pressures 7
• Pain intensity during the procedure, which heightens vagal tone 3
• Paracervical anesthesia administration, which paradoxically increases bradycardia risk through inadvertent intravascular injection of local anesthetic 8

Clinical Recognition

Vasovagal syncope during hysteroscopy presents with:

• Bradycardia (heart rate typically drops significantly from baseline)
• Hypotension due to concurrent vasodilation—often more severe than bradycardia alone would suggest 2
• Pallor, diaphoresis, nausea, and potential loss of consciousness 1
• Patient distress or inability to communicate discomfort 7

Critical pitfall: The hypotension may be disproportionate to the degree of bradycardia because of unappreciated vasodilation, requiring treatment of both components 2

Immediate Management Algorithm

Step 1: Stop the Procedure

• Immediately cease hysteroscopy and remove instruments 7
• Position patient supine or in Trendelenburg to restore venous return 2

Step 2: Supportive Measures

• Ensure adequate oxygenation and ventilation 4
• Restore venous return through positioning and fluid administration 2

Step 3: Pharmacologic Intervention

• Administer atropine 0.5-1 mg IV for persistent bradycardia, repeatable every 3-5 minutes up to maximum 3 mg 3, 4
• Atropine onset occurs within 3 minutes of IV administration 4
• Ephedrine is the most logical single-drug choice because it addresses both bradycardia and vasodilation through combined cardiac and peripheral vascular effects 2

Step 4: Escalation if Needed

• For hemodynamically unstable bradycardia unresponsive to pharmacologic therapy, initiate transcutaneous pacing 5
• Epinephrine must be used early in established cardiac arrest 2

Prevention Strategies

Pre-procedure Optimization

• Administer oral NSAIDs one hour before the scheduled procedure 7
• Use vaginoscopic approach (no speculum) whenever possible to minimize cervical manipulation 7
• Select the smallest diameter hysteroscope adequate for the procedure 7
• Instill saline at the lowest possible pressure to achieve satisfactory visualization 7

High-Risk Patient Preparation

For patients with multiple risk factors (age >60, baseline HR <60, beta-blocker use, ASA III-IV):

• Place transcutaneous pacing pads before beginning the procedure 5, 4
• Review and consider holding negative chronotropic medications 5, 6
• Ensure atropine is immediately available at the bedside 5, 4
• Implement continuous heart rate monitoring throughout the procedure 5, 6

Technique Modifications

• Avoid routine paracervical anesthesia when using vaginoscopic approach, as it increases bradycardia risk without clear pain benefit 7, 8
• Consider paracervical block only when speculum use or cervical dilation is anticipated 7
• Use mechanical tissue removal systems rather than bipolar electrodes for polyp removal (less painful, potentially less vagal stimulation) 7

Important Caveats

• Do NOT routinely use conscious sedation for outpatient hysteroscopy, as it does not prevent vasovagal responses and adds respiratory risks 7
• Do NOT place prophylactic transvenous pacing wires—transcutaneous pads are sufficient and transvenous access carries increased risk of ventricular arrhythmias 5, 6
• The clinical team must stop immediately if the patient appears distressed or shows signs of vasovagal episode, even if she cannot verbalize concerns 7
• Low-dose ketamine infusion (0.75 mg/kg bolus, then 10 mcg/kg/min) reduces both pain and the incidence of bradycardia/hypotension during hysteroscopy, though it causes disorientation in 75% of patients 9