What is the recommended management of severe bradycardia (maternal heart rate <50 beats/min with symptoms or hemodynamic compromise) in a pregnant woman?

Management of Severe Bradycardia in Pregnancy

For symptomatic severe bradycardia in pregnancy, immediately reposition the patient to left lateral decubitus position to relieve inferior vena cava compression, and if symptoms persist, proceed with temporary pacemaker placement. 1

Initial Assessment and Immediate Management

First-Line Intervention: Positional Changes

• Change the patient's position to left lateral decubitus immediately to relieve uterine compression of the inferior vena cava, which can cause paradoxical sinus slowing and symptomatic bradycardia (supine hypotensive syndrome of pregnancy). 1
• This simple maneuver may resolve symptomatic bradycardia without further intervention, particularly during labor and delivery when Valsalva maneuvers can trigger reflex cardiac slowing. 1

When Positional Changes Fail

• If symptoms persist despite left lateral positioning, temporary pacemaker placement is necessary. 1
• Temporary pacing is specifically recommended during delivery in selected women with complete heart block and symptoms due to the risk of bradycardia and syncope. 1

Evaluation of Underlying Cause

Determine the Etiology

• Assess for sinus node dysfunction versus atrioventricular blocks, as management differs based on the underlying mechanism. 1
• Bradyarrhythmias may become symptomatic during pregnancy due to increased demands for higher heart rate and cardiac output, particularly in patients with structural heart disease. 1
• Obtain a detailed history including personal cardiac history (previous arrhythmias, structural heart disease, congenital heart disease) and family history of sudden cardiac death or inherited arrhythmia syndromes. 2

Specific Bradyarrhythmia Types

Sinus Node Dysfunction:

• Sinus bradycardia during pregnancy is often benign and related to reflex cardiac slowing during Valsalva maneuvers or supine hypotensive syndrome. 1
• Positional management is typically sufficient unless symptoms persist. 1

Atrioventricular Blocks:

• First-degree AV block can occur in the absence of underlying heart disease and does not progress to complete heart block. 1
• Second-degree AV block (usually type I Wenckebach) is rare and typically unassociated with symptomatic bradycardia. 1
• Isolated congenital complete heart block has a favorable outcome during pregnancy, especially with narrow QRS escape rhythm, and supportive pacing is usually not necessary. 1
• Vaginal delivery carries no extra risks in mothers with congenital complete heart block unless contraindicated for obstetric reasons. 1

Permanent Pacemaker Implantation

Indications and Timing

• Permanent pacemaker implantation (preferably single chamber) is indicated for persistent symptomatic bradycardia that does not respond to conservative measures. 1
• The risks of permanent pacemaker implantation are generally low and can be performed safely, especially if the fetus is beyond 8 weeks gestation. 1
• Use echocardiographic guidance for implantation to minimize radiation exposure to the fetus. 1

Special Considerations for Complete Heart Block

• Thirty percent of congenital AV blocks remain undiscovered until adulthood and may present during pregnancy. 1
• Temporary pacing during delivery is specifically recommended in selected women with complete heart block and symptoms. 1

Pharmacologic Considerations

Atropine Use in Pregnancy

• Atropine crosses the placenta but is not contraindicated for severe or life-threatening bradycardia. 3
• Life-sustaining therapy for the pregnant woman should not be withheld because of concerns regarding effects on the fetus. 3
• Available observational data show atropine use was not associated with increased risk of congenital malformations in multiple surveillance studies. 3
• To minimize infant exposure if breastfeeding, pump and discard milk for 24 hours after atropine use before resuming breastfeeding. 3

Critical Pitfalls to Avoid

• Do not delay necessary interventions due to pregnancy concerns—maternal stability is essential for fetal survival. 4, 5
• Do not assume all bradycardia in pregnancy is benign; asymptomatic bradyarrhythmias may become symptomatic due to increased cardiac demands. 1
• Do not overlook structural heart disease, particularly in patients with congenital heart disease who have undergone corrective surgery (tetralogy of Fallot, VSD repair). 1
• Remember that bradyarrhythmias and conduction disturbances are rare during pregnancy but usually have favorable outcomes in the absence of underlying heart disease. 1

Monitoring and Follow-Up

• Continuous fetal monitoring is essential to assess fetal heart rate and well-being, as maternal bradycardia can cause fetal hypoperfusion. 4
• Regular monitoring of maternal symptoms and fetal well-being throughout pregnancy is recommended. 4, 5, 2