Discussion

The most common cause of aortic stenosis among women of childbearing age is congenital bicuspid aortic valve disease, which accounts for 2% of CHDs.Reference Silversides, Colman, Sermer, Farine and Siu ^{1 –} Reference Fedak, Verma, David, Leask, Weisel and Butany ⁵ On the basis of WHO classification of maternal cardiovascular risk by cardiac condition, severe symptomatic aortic stenosis in pregnancy is classified under WHO class IV. These patients are considered extremely high risk for maternal morbidity and mortality. Data quantifying maternal and fetal risk of pregnancy in women specifically with these high-risk features of aortic stenosis are limited. A systematic search of peer-reviewed literature between 1985 and 2007 on pregnancy in women with structural CHD reported rates of maternal risks including arrhythmias (2.4%), heart failure (7%), and cardiovascular events such as myocardial infarction, stroke, and cardiovascular mortality (2.5%).Reference Drenthen, Pieper and Roos-Hesselink ⁶ Although this study reported no difference in neonatal outcomes when compared with the general population, Hameed et alReference Hameed, Karaalp and Tummala ⁷ reported adverse fetal outcomes such as preterm delivery and intrauterine growth restriction in patients with severe aortic stenosis.

In severe aortic stenosis, there is elevation of ventricular systolic and diastolic filling pressures owing to a fixed stroke volume and limited increase in cardiac output. Patients with aortic stenosis become very sensitive to acute changes in preload and afterload, in which ventricular arrhythmias and heart failure can occur. Symptomatic patients may benefit from admission in a tertiary referral hospital with a specialised unit for close maternal cardiac surveillance, blood pressure control, and heart rate regulation. In our institution, we also keep a STAT caesarean section cart and an infant warmer bedside in case an emergent delivery is necessary and mobilisation of patient to the operating room will cause loss of valuable time. Initiation of antepartum fetal surveillance including monthly growth ultrasounds should be considered during admission, starting at viability, to assess fetal well-being and growth. During the course of our patient’s hospitalisation, she received two full courses of antenatal corticosteroids for promotion of fetal lung maturity and prevention of prematurity-associated complications.

A conservative management strategy was deemed high risk for both the mother and fetus owing to complaint of chest pain associated with intermittent arrhythmias and hypotensive episodes noted on presentation. Treatment options were discussed by a multi-disciplinary team with special attention paid to maternal and fetal risks and feasibility of each option. In addition to the diagnosis of severe aortic stenosis, our patient was found to have severe aortic regurgitation, which might have played a role in her presentation and course. The American College of Cardiology and the American Heart Association have recommended that pregnant patients with severe aortic regurgitation should only be considered for a valve operation if they have refractory NYHA class IV heart failure symptoms.Reference Nishimura, Otto and Bonow ⁸ Overall, aortic regurgitation is better tolerated in pregnancy than aortic stenosis. However, when both conditions present simultaneously in one individual, it might make the management challenging and possibly worsen the prognosis. Information is scarce on the management of pregnant patients with a combination of both aortic stenosis and aortic regurgitation.

Valvular surgery has been performed successfully during pregnancy for many years. However, aortic valve replacement during pregnancy does pose an increased risk of mortality to the mother and fetus (3–15% and 16–33%, respectively).Reference John, Gurley and Schaff ^{9 ,} Reference Chambers and Clark ¹⁰ Balloon aortic valvuloplasty has an overall lower associated risk of complication; however, it has been reported to increase or worsen existing aortic regurgitation. Although there are sparse data on transcatheter aortic valve replacement during pregnancy, the existing data suggest that transcatheter aortic valve replacement performed during pregnancy would likely be successful with a lower risk to the fetus and acceptable maternal risk compared with surgery.Reference Hodson, Kirker, Swanson, Walsh, Korngold and Ramelli ¹¹ Following evaluation, our patient was not an ideal candidate for balloon aortic valvuloplasty owing to already existing severe aortic regurgitation. Additionally, our patient was not a candidate for transcatheter aortic valve replacement owing to significant narrowing of the femoral artery and the absence of calcification on the aortic valve annulus, which would enable anchoring of the prosthetic valve.

The total blood volume rises steadily during the first trimester and is increased by almost 50% by the 30th week, remaining constant thereafter in late pregnancy. Furthermore, the enlarged uterus partially impedes venous return by compressing the inferior caval vein, accounting for lower cardiac output. Ultimately, a decision was made to proceed with delivery and surgical aortic valve replacement at 28 weeks’ gestational age owing to increased frequency of non-sustained ventricular tachycardia and persistent hypotension. However, at 28 weeks there is increased survival rate of the fetus, and beyond this gestational age increased cardiac performance might increase maternal mortality. Of note, the decision to deliver at 28 weeks does not come without risk of morbidity to the neonate, including risk of respiratory distress syndrome, neonatal ICU admission, intraventricular haemorrhage, and necrotising enterocolitis. Nonetheless, when compared with the risk of mortality associated with sudden cardiac arrest or decompensation that may arise in the patient, delivery is a reasonable option.

During delivery, care is best provided through the cooperative efforts of a multi-disciplinary team involving Obstetrics/Maternal Fetal Medicine, Neonatology, Cardiothoracic surgery, and Obstetric Anaesthesia. Decision to proceed with a caesarean section was based on the concern for significant demands on the cardiovascular system during the first and second stages of labour, placing an acute load on the diseased heart.