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A 36 year old Somalian woman presented with severe exertional breathlessness 20 weeks into her sixth pregnancy. She had four successful deliveries previously but suffered a miscarriage a year before this presentation. There were physical signs of severe mitral stenosis. The diagnosis of rheumatic mitral stenosis was confirmed on transthoracic echocardiography with an estimated mitral valve area of 0.8 cm2. There was also echocardiographic evidence of significant pulmonary hypertension (estimated pulmonary artery pressure 90 mmHg) and right ventricular hypertrophy.
Under transoesophageal echocardiography (TOE) guidance, percutaneous balloon mitral valvotomy (BMV) was undertaken from the right femoral vein. A 24 mm balloon dilatation was undertaken with a satisfactory increase in valve area to 1.4 cm2 (see panels). Within 24 hours, the pulmonary artery pressure had fallen to less than 40 mm Hg with a dramatic improvement in patient symptoms. The patient went on to have a successful delivery by planned caesarean section at 38 weeks.
Pregnancy is associated with a 40–50% increase in cardiac output and a decrease in systemic vascular resistance but, in the presence of severe mitral stenosis, these changes cannot occur. Untreated, the haemodynamic effects of mitral stenosis, together with the risk of thromboembolism, can lead to significant maternal and fetal morbidity and mortality. BMV in the second trimester of pregnancy improves haemodynamic indices and maternal and fetal outcomes. Fluoroscopic radiation carries a potential risk to the unborn child, but the use of TOE abolishes the need for a left ventriculogram and reduces the overall radiation dose.