hEART
VALVES IN PREGNANCY
DR. HASSAN
CHAMSI-PASHA
MD, FRCP(Lond),FRCP(Glasg),FRCPI,FACC
Published in Journal of Saudi Heart Association
Pregnancy
causes dramatic, usually reversible, changes in a woman’s cardiovascular
system. Maternal heart disease (present
in 2%) of all pregnancies is the most important non-obstetric cause of death in
pregnant women. Valvular heart disease
may have a significant impact on fetal and maternal health during pregnancy,
labor, and delivery. Pregnant women with
valvular heart disease should be managed by a high-risk obstetric service that
can provide cardiology consultation, close obstetric supervision and provisions
for delivery with hemodynamic monitoring when required.(1)
Valvular heart lesions
associated with high maternal and/or fetal risk during pregnancy include severe
aortic stenosis, aortic and mitral regurgitation with functional class III-IV
symptoms, mitral stenosis with class II-IV symptoms, aortic and/or mitral valve
disease resulting in severe pulmonary hypertension or associated with severe LV
dysfunction and mechanical prosthetic valve requiring anticoagulation. On the
other hand, valvular heart lesions
associated with low maternal and fetal risk include asymptomatic mild to
moderate aortic stenosis with normal LV systolic function, aortic or mitral
regurgitation with NYHA functional class I or II with normal LV systolic
function, mitral valve prolapse with mild to moderate MR, and mild to moderate
mitral stenosis without severe pulmonary hypertension.(2)
Young pregnant
women with a previous history of acute rheumatic fever and carditis should
continue to receive penicillin prophylaxis as indicated in the non-pregnant
state. The most common rheumatic lesion
in this age group remains mitral stenosis (MS). Patients with mild to moderate
MS can almost always be managed with judicious use of diuretics and B-blockade.
Diuretics are given to relieve pulmonary and excess systemic venous congestion.
Patients with severe MS who are symptomatic before conception should be
considered for percutaneous balloon mitral valvotomy before conception. Patients with severe MS who develop NYHA
functional Class III-IV symptoms during pregnancy should undergo percutaneous
balloon valvotomy.(2) The reported
results with mitral balloon valvotomy have been excellent.(3) In developing countries, there is a long
history of successful surgical closed commissurotomy for pregnant women.
Patients with
mitral regurgitation (MR) usually tolerate pregnancy and can be managed
medically. Medical management includes
diuretics for patients with pulmonary congestion. Vasodilator therapy is indicated only in the
presence of concomitant systemic hypertension and should not be advised in the
setting of normal or low systemic blood pressure. ACE inhibitors are considered unsafe in
pregnancy while hydralazine and nitrates are known to be safe.
Patients with
mild to moderate aortic stenosis (AS) and normal LV systolic function can
usually be managed conservatively through the entire pregnancy. Patients with pressure gradient >50 mm Hg
or symptoms should be advised to delay conception until relief of AS can be
obtained. For those with severe AS whose disease is first appreciated during
pregnancy, consideration may have to be given to either percutaneous aortic
balloon valvotomy (4) or surgery before labor if heart failure has developed or
syncope has occurred. These procedures
are fraught with danger to both the mother and fetus.
Isolated aortic
regurgitation (AR), like MR, can usually be managed medically with a
combination of diuretics and, if necessary, vasodilator therapy. Women with
symptoms and/or signs of LV failure should be carefully monitored throughout
labor and delivery with strict attention to volume status and blood pressure.
The approach to
the patient with tricuspid valve involvement as part of a more complex
congenital or acquired heart disease is predicated on the features of the
associated lesions. Isolated TR should
not pose a significant problem, although greater care may be necessary to
protect against diuretic-induced hypoperfusion.(2) Vasodilators and digoxin are unlikely to be
beneficial.(5)
The management of
women with prosthetic heart valves during pregnancy poses a particular
challenge as there are no available guidelines for effective antithrombotic
therapy.(6)
Warfarin crosses
the placenta and has been associated with an increased incidence of spontaneous
abortion, prematurity, and stillbirth.
Warfarin embryopathy occurs in 4% to 10% of patients.(7) The risk may be dose-related and appears to
be highest if exposure occurs during the 6th to 12th
weeks of gestation.
Heparin does not
cross the placenta and is generally considered safer. Its long-term use, however, is complicated by
sterile abscesses, osteoporosis, thrombocytopenia, and bleeding. Subcutaneous
administration of heparin has been reported to be ineffective in preventing
thromboembolic complications.(6) Thromboembolic complications, including fatal
valve thrombosis, in high-risk pregnant women managed with subcutaneous heparin
was reported in 12-24% of patients.(8)
Thromboembolism, however, has been reported mostly in patients with
older-generation mechanical valves (Starr-Edwards, Bjork-Shiley and so forth)
in the mitral portion.(5) These findings
led to recommendations included in the American College of Cardiology/American
Heart Association Guidelines for the use of Warfarin as an anticoagulant of
choice for the first 35 weeks of pregnancy in patients with a mechanical prosthetic
valve. These guidelines state that “the
decision whether to use heparin during the first trimester or to continue oral
anticoagulation throughout pregnancy should be made after full discussion with
the patient and her partner; if she chooses to change to heparin for the first
trimester, she should be made aware that heparin is less safe for her, with a
higher risk of both thrombosis and bleeding.
High-risk women who choose not take warfarin during the first trimester
should receive continuous heparin intravenously. Transition to warfarin can occur
thereafter”(2).
These
recommendations have been problematic and have not been adopted by both
patients and physicians, especially in United States. Women in general are not willing to take
warfarin during the first trimester of pregnancy.(5) The attitude of physicians is reflected by
the fact that 96% of 438 members of the Society of Perinatal Obstetricians
surveyed on their preferred management of a pregnant patient with a mechanical
prosthesis in the mitral position selected discontinuation of warfarin and use
of full-dose heparin for the duration of pregnancy.(9)
Vitale et al
recently made an important contribution demonstrating a close dependency
between warfarin dosage and fetal complications. In his study, 22 of 25
pregnant women (88%) whose warfarin dose was >5 mg/day had fetal
complications with a 9% incidence of warfarin embryopathy. In contrast, only 5 of 33 cases (15%) treated
with a small dose warfarin (< 5 mg/day) had fetal complications
and non of them had warfarin embryopathy.(10)
These findings may suggest the feasibility of risk free use of warfarin
during pregnancy in patients with prosthetic heart valves who can be well
anticoagulated with < 5 mg of warfarin per day.
Meschengieser et
al recently studied 92 pregnancies in 59 women with mechanical heart valve
prosthesis. In 31 pregnancies, subcutaneous heparin was started when pregnancy
was diagnosed and in the second trimester oral anticoagulants were resumed. In 61 pregnancies oral anticoagulants were
continued during the first trimester.
Abortion or fetal losses were similar in the two groups while embolic
episodes were more common (p=.0029) in women who received heparin (4.92%) compared
with those on oral anticoagulants (0.33%).(11)
Recently Chan et
al(6) made a systematic review of the literature and found that the use of oral
anticoagulants throughout pregnancy was associated with warfarin embryopathy in
6.4% of live births. The substitution of
heparin at or prior to 6 weeks, and continued until 12 weeks, eliminated this
risk. The regimen associated with the lowest risk of valve thrombosis (3.9%)
was the use of oral anticoagulants throughout; using heparin only between 6 and
12 weeks’ gestation was associated with increased risk of valve thrombosis
(9.2%).(6)
The additional
use of low-dose aspirin should be considered, particularly in women with
high-risk valves, women with previous transient ischemic attacks and/or strokes, and women with atrial
fibrillation.(12)
A more recent and
theoretically more promising approach consists of therapy with
low-molecular-weight heparins (LMWH), which do not cross the placenta, do not
require frequent partial thromboplastin time monitoring and have a longer
half-life than sodium heparin.(1) There
is a great deal of interest in the use of LMWH as a substitute for
unfractionated heparin in patients with prosthetic heart valves during
pregnancy. The data to support the use
of LMWH, however, is not yet available.
A successful use of LMWH was reported in small number of patients and
more information is required before LMWH can be recommended for anticoagulation
in a patient with a prosthetic valve during pregnancy.(5) Recently, two cases of LMWH treatment failure
resulting in thrombosed prosthetic heart valves were reported.(13)
Another important
issue related to pregnancy is whether pregnancy affects the durability of
valvular bioprostheses or not. Anecdotal reports of early failure of biological
heart valves in pregnant patients tend to raise concerns. (14) Recently Salazar et al(15) reported data from
48 women who became pregnant after bovine pericardial valve replacement. Their data confirm recent reports that
pregnancy does not significantly affect durability of bioprosthesis. In their study, the actuarial freedom from
dysfunction was 90.4% at 5 years and 77%
at 8 years for the pregnancy group and 86.3% and 73.4% respectively, for the
control group (p = not significant).
This study, however, has more than one limitation. First, the number of patients is relatively
small, and secondly, the study is limited to the hard end points of death and
reoperation. Conceivably, pregnancy could cause more subtle valvular
dysfunction not detected by analysis of death and reoperation. The primary implication of this study is that
bioprostheses remain the devices of choice for young women willing to trade
earlier operation for the opportunity of pregnancy.(16)
References:
1) Teerlink JR, Foster E.
Valvular Heart Disease in Pregnancy. Cardiol Clin 1998,16:573-95.
2) Bonow RO, Carabello B, de Leon AC Jr, Edmunds
LH Jr, Fedderly BJ, Freed MD, Gaasch WH, McKay CR, Nishimura RA, O’Gara PT, O’Rourke RA, Rahimtoola SH.
ACC/AHA guidelines for the management of patients with valvular heart disease:
a report of the American College of Cardiology/American Heart Association Task
Force on Practice Guidelines (Committee on Management of Patients With Valvular
Heart Disease). J Am Coll Cardiol. 1998;32:1486-588.
3) Martinez-rios MA, Tovar S,
Luna J, Eid-Lidt G. Percutaneous Mitral
Commissurotomy. Cardiol Review 1999,7:108-16.
4) Banning AP, Pearson JF, Hall
RJ. Role of balloon dilatation of the
aortic valve in pregnant patients with severe aortic stenosis. Br Heart J 1993;70:544-45.
5) Elkayam U. Pregnancy through
a prosthetic heart valve. J Am Coll Cardiol 1999;33:1642-5.
6) Chan WS, Anand S, Ginsberg
JS. Anticoagulation of pregnant women with mechanical heart valves: a
systematic review of the literature. Arch Intern Med 2000;160:191-6.
7) Hirsh J, Fuster V. Guide to
anticoagulant therapy, part 2: oral anticoagulants. American Heart
Association. Circulation 1994;89:1469-80.
8) Elkayam UR. Anticoagulation
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9) Evans W, Laifer SA, Mc Nanley TJ et al. Management of thromboembolic disease
associated with pregnancy. J
Maternal-Fetal Med 1997;6:21-7.
10)Vitale N, de
Feo M, de Santo LS, Pollice A, Tedesco N, Cotrufo M.
Dose-dependent
fetal complications of warfarin in pregnant women with mechanical heart valves.
J Am Coll Cardiol 1999;33:1637-41.
11)Meschengieser SS, Fondevila CG, Santarelli MT, Lazzari MA. Anticoagulation in pregnant women
with mechanical heart valve prostheses. Heart 1999; 82:23-6.
12)Chan WS. What is the optimal
management of pregnant women with valvular heart disease in pregnancy? Haemostasis
1999,29 suppl S1:105-6.
13)Lev Rano, Kamer A, Gurevitch
J, Shapira, Mohr R. Low-molecular weight heparin for prosthetic heart valves: treatment
failure. Ann Thoracic Surg 2000; 69: 264-5.
14)Jamieson WR, Miller DC, Akins CW et al. Pregnancy and bioprostheses:
influence on structural valve deterioration. Ann Thorac Surg 1995; 60:S
282-86.
15)Salazar F, Espinola N, Roman L, Casanova JM. Effect
of pregnancy on the duration of bovine pericardial bioprostheses. Am Heart J
1999;137(4 Pt 1): 714-20.
16)Glower DD. Does pregnancy
affect the durability of valvular bioprostheses? Am Heart J 1999;137(4 Pt1):590-1.