Optimizing Anticoagulation in Pregnancies With Mechanical Heart Valves

Condition(s) studied

Investigational drug(s) / intervention(s)

LMWH and LDA: 1\) Therapeutic LMWH throughout pregnancy either using weight-based dosing or dosing according to anti-Xa levels. The initial dose will be a twice daily therapeutic dose of 1.35U/kg (pregnancy weight) of enoxaparin or 135 U/kg (pregnancy weight) of dalteparin using prefilled syringes titrated to the higher dose prefilled syringe (i.e., not below the pregnancy weight-based dosing). 1. The dose of therapeutic LMWH can be adjusted by anti-Xa (done at least after four days of the start of LMWH or change in LMWH dose) levels or by pregnancy weight however, weight and anti-Xa levels will be determined for all participants using LMWH. Pregnancy weight in kilograms is to be determined every month. 2. If therapeutic LMWH is adjusted according to anti-Xa levels, peak and trough anti-Xa levels (done at least after four days of the start of LMWH or change in LMWH dose) are to be sent every four weeks or weekly if there is a change in dose.

Vitamin K antagonists (e.g warfarin)+/- LDA: VKAs during pregnancy: VKA use will require INRs every two weeks or weekly (done at least 5 days after starting or changing the dose) if there is a change in doses to ensure an INR of 2.5 for a patient with an aortic MVR (INR of 2 for the On-X AVR) and 3 for mitral MVR or two MHVs is met. LDA 81 mg to be added once pregnancy is confirmed.

Sequential therapy +/- LDA: LMWH at 6 weeks gestation until 12 weeks gestation prescribed according to the regimens above then VKAs from 12 weeks gestation until 34-36 weeks gestation followed by twice daily LMWH according to doses above until delivery. LDA to be added when pregnancy is confirmed

Study summary

The purpose of this pilot study is to collect data on pregnancies with mechanical heart valves to see if using a blood thinner called low molecular weight heparin (LMWH) and low dose aspirin (LDA) is comparable to warfarin/vitamin K antagonist (VKA) to reduce the chance of clotting around the mechanical valve and improve survival. The study is a pilot study as the study investigators need to ensure that the blood levels needed for adequate amounts of LMWH and warfarin can be maintained during pregnancy to be able to compare LMWH and aspirin to warfarin. If this study shows that we can collect the tests that are needed for a larger study, the individuals' information who participated in this pilot study will be moved to the larger study. The larger study will compare survival, clot development and cardiac function as well as safety of these two common blood thinners.

Eligibility

Primary outcome measure(s)

• Primary outcome Measures — At baseline
  1\) Enrollment rate: To determine enrollment rate as defined by the number of patients enrolled/patients eligible, and consent rates (consent obtained/patients approached)
• Adherence rate — From enrollment until birth.
  To determine the adherence rate as defined as adherence to the anticoagulation regimen in 80% or more of the pregnancy.

Trial sites (1)

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