hEART VALVES IN PREGNANCY
DR. HASSAN CHAMSI-PASHA
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 in pregnant women with prosthetic heart valves: a double
jeopardy. J Am Coll Cardiol 1996;27:1704-6.
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.