BARCELONA – Women with mechanical heart valves who become pregnant face a very-high-risk pregnancy, with a 58% rate of an uncomplicated pregnancy resulting in a live birth, according to international registry data collected since 2007.

Pregnant women at high risk because of a mechanical heart valve need management by a multidisciplinary team at a referral center that focuses on these cases, a type of care that many of these women do not receive today, Dr. Jolien W. Roos-Hesselink said at the annual congress of the European Society of Cardiology.

“We believe management of these women needs to be better structured and organized,” said Dr. Roos-Hesselink, professor and head of the department of congenital cardiology at Erasmus Medical Center in Rotterdam, the Netherlands. “Pregnancy is a time of risk for any woman with structural heart disease, but for those with a mechanical valve are really high-risk patients,” she said in an interview.

“Most of these women are now cared for by a general cardiologist. They need a specialist in obstetric cardiology,” as well as care from other experts with experience in the types of complications these woman develop, said Dr. Roger J.C. Hall, professor of cardiology at Norfolk and Norwich (U.K.) University Hospital.

The data also showed that physicians around the world used any one of seven different anticoagulant regimens during these pregnancies, a strikingly high number that highlights uncertainty about which regimen is best, although heparin use during the first trimester was linked with a higher rate of valve thrombosis. The various regimens use different combinations of periods of treatment with unfractionated heparin, low-molecular-weight heparin, or a vitamin K antagonist drug during the first trimester, during weeks 14-36, and during the last weeks of pregnancy.

“We found large differences in management among different countries, physicians, and among individual patients. All the regimens have advantages and disadvantages” and are based on expert opinion with no prospect for a randomized, controlled trial, said Dr. Roos-Hesselink. For now, the numbers of women receiving each of the seven regimens remains too small for statistical analysis, but the researchers hope that eventually larger numbers may start to reveal which regimens work best, said Dr. Hall.

However, the available data showed two clear trends: Treatment with vitamin K antagonists was tied to an increased rate of miscarriages, and treatment with heparin during the first trimester was associated with an increased rate of valve thrombosis, noted Dr. Roos-Hesselink.

One other notable finding was that the risks faced by women with mechanical heart valves far exceeded the risk seen in women with tissue valves, and in women with other forms of mechanical heart disease but no valve prostheses. Adolescents and young women who need a heart valve should be part of a shared decision process that reviews the pros and cons of a mechanical and tissue valve, said Dr. Roos-Hesselink and Dr. Hall. A tissue valve is less durable, and so typically requires replacement sooner than does a mechanical valve. But in the current study, the pregnancy loss and complication rates among the 134 women with a tissue valve roughly matched the rates among the 2,620 women with no valve prosthesis, while the rates among 212 women with a mechanical valve ran much higher.

The Registry of Pregnancy and Cardiac Diseases began in 2007 through an initiative of two interest groups of the European Society of Cardiology, the valve group and the congenital heart disease group (Eur. Heart J. 2013;34:657-65). By September 2014, the registry had enrolled more than 3,600 pregnancies. The current report focused on the first 2,966 women enrolled, with an average age of 29 years. Slightly more than half the enrolled women had congenital heart disease, slightly fewer than a third had valvular heart disease (usually because of rheumatic heart disease), 7% had cardiomyopathy, and smaller number of women had other etiologies.

Maternal mortality averaged 1.4% for women with mechanical valves, 1.5% for those with tissue valves, and 0.2% for everyone else. Miscarriage rates were 16% for mothers with mechanical valves and 2% for everyone else, including those with tissues valves. Fetal mortality was 3% among women with mechanical valves and less than 1% for everyone else. Thrombotic and hemorrhagic events occurred in about 29% of women with mechanical valves, compared with less than 6% in everyone else. Ten of the women with mechanical valves (5%) developed valve thrombosis. The live birth rate was 80% for women with mechanical valves and 95% or better for everyone else.

Dr. Roos-Hesselink and Dr. Hall had no disclosures.

mzoler@frontlinemedcom.com

On Twitter @mitchelzoler

Mechanical heart valves create high pregnancy risk