Mechanical Valves in Pregnancy: Scant Progress, Big Risks

Shelley Wood

September 02, 2014

BARCELONA, SPAIN — Pregnant women with mechanical valves continue to face significantly higher risks of complications and death than pregnant cardiac patients with no prostheses, according to some of the first contemporary data to address this complex issue.

Moreover, as Dr Jolien Roos-Hesselink (Rotterdam, the Netherlands) showed here at the European Society of Cardiology 2014 Congress , there is a wide variety in the types of anticoagulation regimens these women with prosthetic valves are following during pregnancy, with fewer than half following a guideline-recommended strategy.

The data highlight the need for this group to be followed at specialized centers, she said. "I think what is happening now, if you have in your hospital a patient with a complex congenital lesion, you'll probably send her to a tertiary center. But if you have a patient with a mechanical valve, most doctors feel they can treat this patient through pregnancy. I'm afraid this is really a high-risk patient group and . . . we should take care of them in specialized centers." This entails a team that includes an obstetrician, an anesthesiologist, a cardiologist, and someone really specialized in hematological complications.

Registry of Pregnancy and Cardiac Disease

Roos-Hesselink and colleagues drew on data from the ongoing, worldwide Registry of Pregnancy and Cardiac Disease ,ultimately comparing 212 patients with mechanical valves with 2620 cardiac patients with no prostheses.

Not surprisingly, rates of maternal mortality, thrombotic events, hemorrhagic events, miscarriage, and fetal mortality were all significantly higher among the women with mechanical valves.

Adverse Events, Mechanical Valve vs Other Cardiac Patients

Event Mechanical valve (%) Cardiac patients, no prosthesis (%)
Maternal mortality 1.4 0.2*
Thrombotic event 6.1 0.4*
Hemorrhagic event 23 5*
Miscarriage <24 weeks 15.6 1.7*
Fetal mortality >24 weeks 2.8 0.6*
*p<0.05

Overall, the rate of event-free live births in women with mechanical valves was just was 58%, vs 78% in other pregnant cardiac patients and more than 90% in women with no cardiac disease.

Dr Bernard Iung (Bichat Hospital, Paris, France), one of the session moderators, observed that these numbers are "very consistent with what has been published previously, mainly 20 years ago, and it's surprising to see that even a contemporary registry . . . found roughly the same figure regarding maternal mortality, thrombotic complications, pregnancy issues, and fetal outcomes [as two decades ago], and that illustrates just how difficult a problem [this is]."

Investigators also studied the anticoagulation regimen followed by the women in their registry and, to their surprise, identified at least seven different patterns of anticoagulant use. "We really were shocked by all the differences [in anticoagulant use] in this worldwide registry," she said.

The most common was a combination of unfractionated heparin (UH) in the first trimester, a vitamin-K antagonist (VKA) in the second trimester, and low-molecular-weight heparin or unfractionated heparin (LMWH/UH) in the third trimester—not a guideline-recommended anticoagulation regimen for this patient group.

But just 20% of women with mechanical valves in the registry were following guideline-recommended VKAs for trimesters 1 and 2 followed by LMWH/UH, or the second recommended strategy: LMWH, VKA, and LMWH/UH for each trimester, respectively.

When that analysis was paired with data on hemorrhagic events, no strategy was significantly worse than another. But for live births, there were striking differences between regimens. In particular, VKAs were associated with rates of miscarriage, while heparin in the first trimester was associated with higher rates of valve thrombosis.

Importantly, Roos-Hesselink stressed, "No one regime turned out to be clearly optimal," underscoring the dire need for better research in this area.

Commenting on the study, Dr Genevieve Derumeaux (Charles Nicolle University Hospital, Rouen, France) pointed to the fact that the registry had a high proportion of women with rheumatic heart disease, reflecting their country of origin and suggesting that "interregional issues . . . along with social and economic environment" also play a role.

Roos-Hesselink agreed, pointing to Egypt as an example of a country with high rates of rheumatic heart disease, mitral stenosis, and mechanical-valve use.

"In these countries, I think the level of care is really excellent, but there are cultural influences. A lot of these patients do not come to see a doctor before they are contemplating pregnancy. They come to the doctor when they are already 20 weeks' pregnant because it is so important in these countries to have a family and to raise a family," she said. "They don't want to hear that they cannot become pregnant or that they are at high risk, so they often come in when they are already [having a] problem."

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