Obstetric cardiology

Question 1

What is the mortality rate of a foetus whose mother undergoes cardiopulmonary bypass?

Answer 1

15-30%

Question 2

What are the harms of warfarin to a foetus?

Answer 2

Dose dependent increase in risk
Foetal anomalies 5-10%
Miscarriage 30%
Late foetal loss 10%

Question 3

What are the benefits of warfarin to a pregnant female with mechanical valve compared to other anticoagulation?

Answer 3

10% absolute risk reduction of major adverse events (valve failure, thromboembolism and death) compared to Enoxaparin. (15% vs 5%)

Question 4

What is the antithrombotic management of a pregnant female with an established bioprosthetic valve?

Answer 4

Aspirin through pregnancy

Question 5

In the setting of a pregnant female with a mechanical valve, when would you consider adding aspirin?

Answer 5

When on heparin or LMWH

Question 6

What are the risk factors for valve complications in a pregnant female with a mechanical valve?

Answer 6

Old or small mechanical mitral valve
Atrial fibrillation or flutter
Previous thromboembolism
Multiple mechanical valves

Question 7

What is the anticoagulant strategy for pregnant females with mechanical valves at the end of term? (On warfarin or on LMWH)

Answer 7

If on LMWH

1. Hold enoxaparin 24 hours prior to induction/caesarean
2. Transition to heparin infusion (Without bolus) or prophylactic clexane
3. Aim to cease heparin 4-6 hours before delivery
4. Cease aspirin 7 days prior
5. Initiate anticoagulation 4-6 hours post or as soon as is safe from bleeding POV (heparin without bolus or enoxaparin prophylactic does 6 hours after and 0.75mg/kg BD at 12 hours post)

If on warfarin

1. Transition to enoxaparin at week 36 and as above
2. Consider adding aspirin

Question 8

What is the target Factor xa level for BD clexane for a pregnant female with mechanical valves?

Answer 8

Aortic 0.8-1.0
Mitral 1.0-1.2

4-6 hours post dose