A 28-year-old woman comes to the office due to exertional shortness of breath for the last 2 weeks. She and her husband recently immigrated to the United States from Cambodia. She has a history of rheumatic mitral stenosis with an estimated mitral valve area of 1.5 cm², which was documented on her most recent transthoracic echocardiogram 4 months ago. The patient's exercise tolerance is about 5 blocks of brisk walking at baseline but is currently about 1 block. She has had no recent upper respiratory infection, sore throat, cough, orthopnea, lower extremity swelling, palpitations, syncope, or chest pain. Blood pressure is 108/67 mm Hg, and pulse is 92/min and regular. A diastolic rumble is heard at the apex in the left decubitus position. The lungs are clear on auscultation. Which of the following is the best next step in management of this patient?

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Explanation: 11ec2b69_be3a_124c_8f63_cd83f1929c85_MD0005_00 This patient has known rheumatic heart disease with severe mitral stenosis, defined as a mitral valve area ≤1.5 cm² (normal: 4-6). Patients with mitral stenosis can remain asymptomatic for years and typically experience a gradual onset of symptoms. Dyspnea is often the first manifestation, followed by cough and hemoptysis (due to pulmonary edema) as well as symptoms of right-sided heart failure (eg, peripheral edema, hepatomegaly). Increased cardiovascular demand can hasten symptom development in patients with mitral stenosis. The normal physiologic changes of pregnancy include increases in plasma volume, heart rate, and cardiac output, which cause an increased flow gradient across the mitral valve (evidenced by a prominent diastolic murmur at the apex). This can lead to worsening symptoms in previously stable patients with mitral stenosis. This patient has experienced a relatively abrupt worsening of dyspnea on exertion and should be evaluated for pregnancy as the precipitating cause. (Choice A) Chest x-ray in mitral stenosis may show signs of left atrial enlargement (eg, straightened left heart border, left bronchus elevation); however, these findings are neither sensitive nor specific. Chest x-ray is useful to evaluate volume overload in patients with mitral stenosis but is unlikely to be helpful in this patient with no signs of pulmonary edema. (Choice B) Pulmonary function testing is helpful in diagnosing obstructive (eg, asthma) or restrictive lung disease (eg, interstitial lung disease). However, these conditions are a less likely cause of dyspnea on exertion in this patient with clear lungs and known severe mitral stenosis. (Choice C) Measurement of serum creatinine and electrolytes is indicated when acute renal failure is suspected. Although acute renal failure can present with dyspnea, the dyspnea is usually associated with signs of volume overload (eg, jugular venous distension, pulmonary crackles, peripheral edema). (Choice D) Transesophageal echocardiogram is often performed to confirm severity and to evaluate the subvalvular apparatus in patients with mitral stenosis. However, it is invasive and not needed to evaluate the most likely underlying cause of this patient's worsening dyspnea. Educational objective: The physiologic changes of pregnancy (eg, increased plasma volume and heart rate) cause an increase in flow gradient across the mitral valve, and can lead to worsening symptoms in previously stable patients with mitral stenosis. References: 2014 AHA/ACC guideline 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. (http://www.ncbi.nlm.nih.gov/pubmed/24603191)

A 28-Year-Old Woman Comes to the Office Due to Exertional