eComment: Are low molecular weight heparin effective in mechanical valve prosthesis anticoagulation during pregnancy?

We read with great interest the report by Carnero-Alcazar and co-workers regarding the successful mechanical mitral valve replacement due to pros-thetic valve thrombosis in a first trimester pregnant woman w1x. Two percent of all pregnant women suffer from some kind of cardiac pathology. Although this incidence varies in different countries, cardiac disease is the leading cause of death in pregnancy w2x. Many factors are associated with pregnancy in cardiopathic patient such as social, ethical and maternal desire for decision whether the pregnancy will be terminated or maintained. When a cardiac problem requires an operation during pregnancy the risks are inevitably increased and substantial efforts must be made to reduce the risk. There are several cases reported in the literature of cardiopulmonary bypass (CPB) used on pregnant women at various stages of pregnancy w2–4x. Many factors associated with cardiac operations requiring CPB can adversely affect both the mother and the fetus, but the embryo-fetal mortality is found that highly increased under hypothermic conditions than the normothermic conditions although maternal mortality did not differ at different temperatures w2x. Younger gestational age and a greater degree of hypothermia are known to increase fetal morbidity during CPB w3x. Cardiophatic pregnant patients can be separated into two groups. One of them is pregnant women who have cardiac pathologies and the other is pregnant women who require emergent surgical interventions. The cardi-opathic patient, even if well compensated, can easily sustain acute heart failure caused by the increase of cardiorespiratory requirements during pregnancy. Ideally, valve disease should be evaluated before pregnancy and treated if necessary. However, pregnancy is often already present when the patient presents. In such cases, if possible, it is always preferable to delay surgery until the time the fetus is viable and a caesarean section can be performed as part of a concomitant procedure w4x. On the other hand, medical therapy is not always sufficient to drive a heart with a reduced functional reserve and acute complications, such as the thrombosis of a valvular prosthesis, endocarditis or acute aortic dissection, which can seriously compromise the heart functions of the pregnant woman. When the open heart operation is necessary to save the patient's life in such situations, the fetus could be seriously compromised after exposure to cardiopulmonary bypass. High-flow, high-pressure, normothermic bypass offers the least risk to the fetus. Fetal heart and uterine monitoring is essential to allow adjustments to the flow to ensure adequate …