11.4.4 Heart valve disease and pregnancy

The most common valvular pathologies in young women are mitral stenosis, aortic stenosis due to bicuspid valve coarctation or ARF, mitral insufficiency (MI) and aortic insufficiency (AI). In general, stenosis is a dangerous limitation of cardiac output, whereas insufficiency is well tolerated due to the arterial vasodilatation of pregnancy, but may lead to left-sided decompensation. If valvulopathy decompensates during pregnancy and threatens the mother's survival, the therapeutic strategy will depend on a number of factors [6].

• If anatomy permits, percutaneous balloon dilatation valvuloplasty is the first choice for mitral stenosis. Anatomically favourable aortic stenosis is less common, where the risk of secondary valve failure and embolization of sclerotic fragments is greater.
• Valve replacement on bypass surgery is only considered when other options have failed or are not feasible, as maternal mortality is 1-5% and fetal mortality is 10-30% [2,11,17,18,20].
• The most favourable time for surgery is the 2nd trimester, when organogenesis is complete and before haemodynamic changes and uterine excitability are at their maximum.
• If the decompensation occurs in the 3rd trimester and the foetus is viable, a caesarean section can be performed before the cardiac operation (ideal time between the two operations: 24-48 hours).
• Valvular insufficiency can generally be controlled with vasodilators and diuretics. In cases of severe LV failure and dilatation, termination of pregnancy or premature delivery may be necessary.
• When aortic insufficiency is secondary to dilatation of the ascending aorta, as in Marfan syndrome, the therapeutic criterion is the diameter of the aorta, given the risk of dissection and rupture.
• Native valvular disease does not require antibiotic therapy.

The aim of treating valvulopathy in pregnancy is to reduce symptoms, save the woman in labour and, if possible, allow the baby to develop to term; it is not aimed at the long-term future of the mother [4,14,19].

 Mitral stenosis

Mitral stenosis is the most common heart valve disease in pregnant women. It is associated with near-fixed cardiac output. It is very poorly tolerated in pregnancy once the mitral surface area is < 1.5 cm², even if the patient is previously asymptomatic [4,19]. The gradient across the valve is proportional to the cardiac output (CO); as the latter increases during the second half of pregnancy, the transmitral gradient increases by 25-50% and the pressure in the left atrium increases. This leads to congestion and pulmonary oedema (APO). On the other hand, the tachycardia that comes along with the increase in CO dangerously shortens diastole: the volume passing through the mitral valve decreases, which in turn increases the LA pressure. The incidence of APO is about 40% in moderate stenosis (S = 1.5 cm²) and 60% in severe stenosis (S < 1.0 cm²); the rate of AF is 15% and 30% respectively [17]. Treatment should include a beta-blocker and a diuretic [6]. Maternal mortality increases with worsening clinical status. From 1% in class I-II, it rises to 5% in class III and 14-17% in class IV, particularly in the presence of AF [10]. Mitral stenosis is associated with a high rate of preterm birth, intrauterine growth retardation, miscarriage and fetal death, especially in cases of APO [5,17]. Caesarean section is often preferred to avoid the difficulties of prolonged labour, but vaginal delivery may be possible if epidural analgesia blocks sympathetic discharges sufficiently to prevent tachycardia and if autotransfusion due to labour is tolerated [8].

 Mitral regurgitation

Second in frequency, mitral insufficiency (MI) is generally well tolerated, especially during pregnancy, when moderate vasodilatation and tachycardia improve haemodynamics. Only 5% of cases are complicated by APO and 4% by atrial tachyarrhythmia [17]. Mitral valve prolapse is generally well tolerated. However, sympathetic stimulation may increase peripheral resistance and increase regurgitation. If MI is secondary to LV dilatation, the prognosis depends on the degree of LV failure. Caesarean section under spinal anaesthesia or vaginal delivery under epidural anaesthesia is feasible.

Aortic stenosis

Aortic stenosis is usually due to bicuspid aortic valve disease. Bicuspid aortic valve disease may be associated with dilatation of the ascending aorta or coarctation. The fixed cardiac output imposed by aortic stenosis causes haemodynamic deterioration in 10-20% of mothers with the disease; maternal mortality is currently < 1% [6,15]. However, mortality from left-sided failure can be as high as 11% when the mean gradient is > 50 mmHg (tight stenosis), with a peak in the peripartum period [18]. Tachycardia and atrial fibrillation are poorly tolerated. The drop in preload (hypovolaemia) is dangerous and afterload must be maintained with a vasoconstrictor in minimal doses to maintain blood pressure without risk of placental ischaemia. However, there is no medical treatment for aortic stenosis. As it is absolutely necessary to maintain preload and peripheral resistance, spinal anaesthesia is contraindicated. Epidural anaesthesia is possible in stable cases, provided the block is introduced very gradually and low concentrations of local anaesthetic are used; in symptomatic narrow stenosis, caesarean section under general anaesthesia is preferable [3,14].

 Aortic insufficiency

Even more than in MI, the moderate vasodilatation and tachycardia of pregnancy improve the haemodynamic situation in aortic insufficiency (AI), but the situation may deteriorate with sympathetic stimulation during labour and delivery. The risk depends on the degree of the parturient's symptoms and the degree of dilatation of her LV. As long as the latter is normal, pregnancy is well tolerated [6]. AI may be associated with dilatation of the aortic root and ascending aorta, as in Marfan syndrome; this situation carries a high risk of dissection (type A) and rupture. For this reason, pregnancy is contraindicated if the aortic diameter is > 4.5 cm [7,14]. Antihypertensive medication, a beta-blocker (sotalol) and very close echocardiographic monitoring are required once the diameter of the ascending aorta exceeds 4.0 cm.

In the case of AI, the spinal region is a good choice for delivery. However, if the ascending aorta is dilated, hypertensive crises associated with vaginal labour should be avoided because of the risk of acute aortic dissection; a planned caesarean section is safer, whether under spinal, epidural or general anaesthesia.

 Tricuspid regurgitation and pulmonary insufficiency

Tricuspid regurgitation is generally well tolerated due to the low pressure regime of the right heart. It is usually secondary to ARF or endocarditis. The situation is very different when it is part of a congenital condition such as Ebstein's disease, or when it occurs in a situation where the RV functions as a systemic ventricle (corrected transposition of the great vessels); it is then an independent predictor of complications.

Pulmonary valve regurgitation is most commonly seen as a residual lesion of corrected tetralogy of Fallot in childhood. It causes volume overload and dilatation of the RV, leading to right-sided failure and ventricular arrhythmias. As long as the RV is of normal size and function, pregnancy can proceed unhindered; the prognosis depends on the degree of right-sided dilatation and failure [7].

 Prosthetic valves

Bioprostheses are usually recommended for women who wish to have children to reduce the risk of thromboembolism and anticoagulation. This advantage is offset by a rate of structural deterioration that limits the life of these valves to around twelve years, although new homograft models have a longer life expectancy. This means that patients are condemned to a second heart operation at a later date to fit a long-lasting mechanical valve. During pregnancy, women with prosthetic valves have a mortality rate of between 1% and 4% (currently 1.5%), mainly due to thromboembolic or haemorrhagic problems [16,19]. The complication rate is approximately 20% for bioprostheses and 40% for mechanical prostheses [6]. With all prosthetic valves, there is a trend towards increased prematurity, delayed weight and height and post-partum haemorrhage.

The main problem is anticoagulation. Without going into the details of anticoagulation in pregnant women, we can mention the following [1,6,13,14,21].

• Anti-vitamin K agents (AVK) are teratogenic in the first trimester, associated with abortus in the 2nd and 3rd trimesters, and associated with neonatal intracerebral haemorrhage in vaginal delivery.
• Low molecular weight heparin (LMWH) therapy, which is not associated with fetal pathology, is the recommended treatment for pregnant women, aiming for anti-Xa activity levels of 0.8-1.2 IU/mL at peak activity and ≥ 0.5 IU/mL at nadir; however, the dose of LMWH required to achieve this goal is higher due to the state of hypercoagulability.
• The new oral anticoagulants (dabigatran and rivaroxaban) are contraindicated in pregnancy and breastfeeding.
• Apart from the first 3 months after implantation, bioprostheses require only aspirin (≤ 150 mg/d).

•  During the first trimester, mechanical mitral valve prosthesis: AVK if a low dose is sufficient to maintain the INR within the desired limits (< 2 mg acenocoumarol, < 3 mg phenprocoumon, < 5 mg warfarin); otherwise LMWH with a target anti-Xa activity of 0.8-1.5 IU/mL at peak activity and ≥ 0.7 IU/mL at nadir.
• During the first trimester, mechanical aortic prosthesis: LMWH with a target anti-Xa activity of 0.8-1.2 IU/mL at peak activity and ≥ 0.5 IU/mL at nadir.
• AVK during the 2nd and 3rd trimesters, despite the risk of abortus.
• Add aspirin (100 mg/d) throughout pregnancy.
• Peripartum: switch to LMWH or UFH.  

• Worsening LV dilatation and dysfunction (EF < 35%);
• Marfan syndrome with AI and ascending aortic dilatation > 4 cm;
• Symptomatic narrow aortic or mitral stenosis that cannot be dilated percutaneously.