Discussion
This single-center study delineates the safety and efficacy of two types of mitral valve prostheses. The event rate of mitral valve re-replacement was high after MMP, possibly due to poor compliance to the oral anticoagulant treatment, owing to the young women’s desire to become pregnant. Furthermore, our study confirmed the remarkably high success rate of MBP in young women, whereas MMP was associated with an increased risk of postoperative bleeding. Since both prostheses types have advantages and disadvantages, specific patient characteristics must be considered when choosing the appropriate type. [12,13]
A recent report demonstrated that MBP has superior antithrombotic properties and longer durability, whereas MMP is associated with thromboembolism and bleeding events.[5,14] Consistently, our study showed that oral anticoagulant use among young women with MMP is associated with a high risk of postoperative bleeding and abortion, and increased frequency of pregnancy-related complications. Moreover, there was a considerable survival benefit for young women with MBP.
Kaplan–Meier analysis of the long-term survival at 10 years of follow-up after MVR demonstrated a significantly higher survival rate with MBP (88%) than with MMP (63%), despite survival being equivalent between groups for the first three years of follow-up. Subsequent competing risk regression analyses indicated a significant survival difference between groups; however, adjustment for preoperative baseline variables showed no significant difference between groups.
Specific patient characteristics, including child-bearing period, frequency of medical visits and blood tests, as well as the possibility of anticoagulant-related thrombotic and bleeding events and teratogenicity, particularly in pregnant women, influenced the choice of mitral valve prosthesis type in young women. The rate of comorbidities, such as AF, renal failure, obesity, diabetes mellitus, and operative factors were not significantly different between groups. In the future, MBP implantation in young women will benefit from the trans-catheter valve-in-valve technique in cases of structural valve deterioration, thus decreasing the reoperation risk. Furthermore, newer MBPs with longer durability may also be more attractive for young women from the perspective of both the patient and medical care.
Our results match those of the Society of Thoracic Surgeons database report from 2000 to 2007, indicating that the age of women receiving MBP has been significantly reduced, and that the rate of MMP implantation has decreased from 68% to 37% among young women.[15 ] Woo et al reported that young age is not a risk factor for the structural deterioration of MBP, which agrees with our results. Moreover, the authors showed that the freedom from reoperation rates at 10, 15, and 20 years after new MBP due to structural valve deterioration were 91, 76, and 50%, respectively.[16]
Previous studies have shown that only 62% of young women on oral anticoagulants who receive MMP are within an acceptable INR range.[12,17,18]
Applegate et al reported that the structural deterioration of MBP is unclear and possibly a result of calcium and lipids accumulation over the valve surface, and suggested that a complete saline rinse of the MBP more than once before surgery leads to a considerable decrease in structural deterioration frequency.[19] Although older-generation MBPs undoubtedly had limited durability, newer MBPs have excellent long-term durability and performance for > 25 years.[15]
Our results agree with those by Walfisch et al who reported that the use of vitamin K antagonists, such as coumadin, even at doses < 5 mg during pregnancy holds a very high possibility of serious risks to the fetus, especially during the first trimester or at term. However, one of the most common international protocols suggested the substitution of coumadin by heparin between the 6th and 12th gestational week to reduce the risk of teratogenicity. Nevertheless, since coumadin has a long half-life, with a terminal elimination half-life of one week, heparin substitution starting at 6 gestational weeks is too late to avoid teratogenicity.[20]
In our study, abortion was significantly higher in the MMP (15%) than in the MBP group (3%). Moreover, the rate of freedom from anticoagulant-related complications among women in child-bearing period was significantly higher in the latter (81% versus 56%).
The impulse use of MBP in young female patients at childbearing period is explained by the classic surgical recommendation of life-time anticoagulants’ use after MMP, the lower risk of reoperation by using new-generation MBPs, the future possibility of valve-in-valve technique, as well as by the patients’ decision to refusethe activity constraints associated with anticoagulants.7,21
Our study is limited by its non-randomized prospective design and small sample size. Thus, our results should be verified in future studies including a larger prospective randomized study sample.