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.