Mitral stenosis in pregnancy is a well recognised problem. Mitral stenosis is a result of rheumatic fever and can present in a number of different ways. In this article, we shall take a look at the significance of mitral stenosis in pregnancy.
How common is mitral stenosis in pregnancy?
Over the last decade or so, the incidence of rheumatic fever has come down significantly. Despite this, there still exists a large number of cases of mitral stenosis in the community. Many patients who have not experience any symptoms yet may be completely unaware that they have this condition.
Current studies suggest that nearly 9/10 cases of heart disease in pregnancy is due to mitral stenosis (Bhatla et al). This is no doubt a significantly large number. Reassuringly though, new medical research and advanced medical techniques mean that the chances of any harm coming to the mother and baby due to mitral stenosis is low.
The problem with mitral stenosis
Patients who have mild mitral stenosis usually do not have any problems during pregnancy. However, those who have moderate or severe mitral stenosis do not tolerated very well during pregnancy. The assessment of the severity of mitral stenosis can be easily made through echocardiography. Some patients may require an exercise test.
Risk to the mother
The main risk that is associated with mitral stenosis is the heart becoming weak due to the stress of pregnancy. Weakening of the heart muscle may occur only in moderate or severe mitral stenosis. This is particularly common in patients who are in their second or third trimesters.
As the pregnancy progresses, the heart muscle can become weaker and weaker and patients ultimately develop heart failure. Heart failure is a condition where the heart is unable to pump blood effectively throughout the body. Due to heart failure, fluid may accumulate in the body including the lungs (called pulmonary edema) causing breathing difficulty.
Mitral stenosis is often accompanied by an irregular heart rhythm (atrial fibrillation) and this can worsen heart failure as well. The presence of atrial fibrillation along with a weak heart can increase in the risk of development of blood clots in the body (by up to 80%).
Risk during delivery
The primary risk that is associated with delivery is the development of severe heart failure. The degree to which the mother will develop this depends upon how they tolerated the condition during pregnancy and what the degree of heart failure was at the time.
Risk to the baby
There are certain risks to the growing fetus associated with mitral stenosis in the mother. This risk is higher in mothers who have a greater degree of heart failure.
Up to 30% of the child births may be premature. Failure of the fetus to grow appropriately (called intrauterine growth retardation) may be seen in up to 20% of the cases. Up to 3% of the babies may be stillborn.
Managing mitral stenosis in pregnancy
The best way to manage mitral stenosis in childbearing women is to get the condition treated before conception. In other words, it is important for women to receive appropriate counseling and treatment if required if they have mitral stenosis. The best time to do this is before trying to have a baby.
Medical management
Medical management is the main way of managing mitral stenosis in pregnancy.
Complete bed rest and oxygen therapy is the first step in management.
In patients who develop weak hearts and in those who accumulate fluid in the body, diuretic medication may be used in small doses. Using a small dose of beta blockers such as atenolol may reduce the chances of development of pulmonary edema without affecting the growing fetus.
Patients who develop atrial fibrillation and who are at risk of developing blood clots may be placed on some blood thinning medication. Digoxin and beta-blockers are excellent drugs in treating this condition. If this treatment fails, patients may require shock therapy under anesthesia. Blood thinning medication like heparin is given during the first trimester and this can be changed over to warfarin from 12 to 36 weeks. Towards the end of pregnancy, patients will be swapped over again to heparin.
These treatments are usually offered to the patient before they conceive.
Management during pregnancy
In women who are already pregnant and who have discovered that they have mitral stenosis, certain procedures may be performed to treat the condition.
One such procedure is percutaneous mitral commissurotomy. This procedure is ideally performed in the second trimester of pregnancy, though usually it is performed after 20 weeks of gestation. Only selected patients will be considered suitable for this procedure. These include those who have high blood pressure within the lungs (pulmonary hypertension) and a severe degree of heart failure. During this procedure, adequate measures will be taken to prevent exposure of the growing fetus to radiation.
In prospective mothers who fail to respond to these treatments, open-heart surgery and valve replacement may be considered. However, this procedure has certain risks and can result in loss of fetus in 16% to 33% of the cases (Sutton et al)
Management during delivery
Women who have moderate to severe mitral stenosis in pregnancy without evidence of severe heart failure can undergo normal vagina delivery. However, in those who have severe heart failure, a Caesarean section may be offered. Caesarean sections are also offered to women in whom medical therapy and other strategies have not worked.
If women undergo maternal delivery or even caesarian section, epidural anesthesia i.e. anesthesia that is administered into the epidural space of the spine may be preferred. this is because this form of anesthesia can keep the heart rate and blood pressure under control and can prevent the accumulation of fluid in the lungs.
Conclusion
Mitral stenosis is a well-recognised problem in India and can be an issue that needs dealing with during pregnancy. Unfortunately, it is a condition that has numerous complications especially in the second and third trimester. While mild mitral stenosis does not appear to have any significant effect, moderate to severe mitral stenosis can result in heart failure and can compromise blood flow to the fetus. Undergoing screening for heart disease with an echocardiogram prior to conceiving is recommended.
References
Misra M, Mittal M, Singh R, Verma A, Rai R, Chandra G, et al. Prevalence of rheumatic heart disease in school-going children of Eastern Uttar Pradesh. Indian Heart J. 2007;59:42–3
Sutton SW, Duncan MA, Chase VA, Marce RJ, Meyers TP, Wood RE. Cardiopulmonary bypass and mitral valve replacement during pregnancy. Perfusion. 2005;20:359–68.
Reference guideline – http://www.escardio.org/guidelines-surveys/esc-guidelines/guidelinesdocuments/guidelines-pregnancy-ft.pdf