Congenital Complete Heart Block (CCHB) in Pregnancy - Maternal Problems

1. Physiological Conflict: Fixed Heart Rate vs. Pregnancy Demands

• The body compensates partly by increasing stroke volume, but this compensation has limits
• By the third trimester, when demands are highest, compensatory mechanisms can fail
• A previously asymptomatic woman can decompensate during pregnancy and develop symptomatic bradycardia or heart failure
• The vertigos she already has are a warning sign - these are likely due to low cardiac output states, and they will tend to worsen as pregnancy progresses

2. Worsening of Vertigo / Pre-syncope and Syncope

• The mild vertigos she currently has represent transient low-flow episodes (Adams-Stokes type)
• As cardiac demands increase in pregnancy, these episodes can worsen into frank syncope
• Syncopal attacks reported in up to 29% of pregnant women with CHB in one case series (Mandal et al., 21 patients)
• Syncope during pregnancy carries risk of falls, placental abruption, and fetal injury

3. Risk of Developing Heart Failure

• The fixed low heart rate means augmentation of cardiac output depends entirely on stroke volume
• Volume overload of pregnancy (blood volume increases ~1.5 L) combined with fixed rate can cause ventricular dilatation and eventual systolic dysfunction
• In women with particularly slow escape rates (<40 bpm), heart failure can occur even without structural disease

4. Peripartum Period - The Highest-Risk Phase

• During contractions: auto-transfusion of 300-500 mL blood per contraction
• Valsalva maneuver during pushing: can further suppress an already-slow heart rate
• However - textbook data is somewhat reassuring: asymptomatic women with CCHB generally do not require temporary pacing even during labor and Valsalva, provided they are monitored carefully (Fuster and Hurst's The Heart, 15th Edition)
• The immediate postpartum period also carries risk due to sudden volume shifts

5. Need for Permanent Pacemaker Insertion During Pregnancy

• If she becomes symptomatic during pregnancy (worsening vertigo, frank syncope, heart failure), permanent pacemaker implantation becomes necessary
• This can be done safely during pregnancy using echocardiographic guidance to minimize or eliminate radiation exposure to the fetus
• Pacemakers can be placed safely, but the procedure itself carries procedural risk (pneumothorax, infection, lead dislodgement)

6. Fetal / Obstetric Complications

• Intrauterine growth restriction (IUGR): reported in up to 14% of pregnancies with maternal CHB (Mandal series) - likely due to reduced uteroplacental perfusion from low maternal cardiac output
• Oligohydramnios: reported in ~7%
• Preterm labor / delivery: up to 11%, sometimes driven by IUGR requiring early delivery
• Absent or reversed diastolic flow in umbilical vessels (indicating severe uteroplacental insufficiency) requiring preterm cesarean section has been reported

7. Drug-Related Hazards During Labor and Delivery

8. Mode of Delivery and Anesthetic Challenges

• Vaginal delivery is generally safe if she is well-monitored and heart rate is adequate
• Cesarean section (if needed) carries anesthetic challenge: spinal anesthesia can cause hypotension, which in a woman already with low cardiac output is dangerous
• Both spinal and general anesthesia carry special considerations; management requires a multidisciplinary team (cardiologist + obstetrician + anesthesiologist)
• Transcutaneous pacing should be on standby during any delivery

9. Psychological Stress and Monitoring Burden

• She will require increased antenatal surveillance: frequent echocardiograms, 24-hour Holter monitoring, serial fetal growth scans
• The anxiety of close monitoring adds psychological burden
• She should ideally be managed at a tertiary center with maternal-fetal medicine and cardiac expertise

Summary of Risk Stratification