Mitral Stenosis in pregnancy

First 20 weeks represents the most changes and so the major challenge to those with significant cardiac disease.

Across normal mitral valve, pressure gradient increases due to increased heart rate and increased blood volume.
Mitral stenosis:
  • Cardiac output is dependent on valve area
  • Cardiac output is limited if valve area < 1.5 cm2
  • 30-50% increase cardiac output during pregnancy causes decompensation in 2nd or 3rd trimester
Pre-conceptual assessment:
Mild (MV area > 1.5 cm2)
  • Favorable outcome
  • Valve repair before pregnancy not indicated
Moderate
  • Decision to perform valvuloplasty before conception should be based on valve area and exercise tolerance
Severe (MV area < 1.0 cm2)
  • Patients should be offered balloon valvuloplasty before pregnancy
What if already pregnant?
Try to reduce heart rate and left atrial pressure
  • Restrict physical activity
  • Add B-blocker – metoprolol relatively safe and well tolerated by both mother and fetus
  • Restrict salt intake and give diuretics to decrease blood volume

Be careful to avoid hypovolaemia and reduced placental perfusion

Delivery
Early epidural
  • minimises fluctuations in cardiac output
  • reduces atrial pressure
  • reduces pulmonary pressures
 Careful fluid management
Vasoconstrictors
Left displacement of uterus
Semi-elective section if severe MS
Post-partum
Pulmonary oedema often seen in first few hours postpartum but usually responds to diuresis
Severe mitral stenosis should be monitored in intensive care
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