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Difficulty: Very hardCardiovascular System

A 2929-year-old primigravida at 3030 weeks gestation is brought to the emergency department due to rapidly progressive shortness of breath, palpitations, and hemoptysis that began 2424 hours ago. She reports a sense of overwhelming anxiety and impending doom. She has a history of bipolar I disorder, currently well-controlled on lamotrigine, and mild intermittent asthma since childhood. Her temperature is 37.0∘C37.0^\circ\text{C} (98.6∘F98.6^\circ\text{F}), blood pressure is 112/68112/68 mmHg, pulse is 135135 /min and irregularly irregular, and respiratory rate is 2828 /min. Oxygen saturation is 88%88\% on room air and improves to 94%94\% on supplemental oxygen.

Physical examination reveals prominent jugular venous pulsations with absent 'a' waves. Pulmonary auscultation reveals bilateral crackles up to the mid-scapulae with scattered expiratory wheezes. Cardiac auscultation reveals a loud first heart sound, a high-frequency sound in early diastole, and a low-pitched mid-diastolic sound best heard at the apex in the left lateral decubitus position.

Which of the following is the most appropriate next step in management?

  1. A
    Administer nebulized albuterol and intravenous methylprednisolone
  2. B
    Initiate oral sertraline and refer for outpatient psychiatric evaluation
  3. Administer intravenous metoprolol and furosemideAnswer
  4. D
    Administer intravenous piperacillin-tazobactam and vancomycin
  5. E
    Reassure the patient and recommend elevating her legs at night

Answer

The correct next step is to administer intravenous metoprolol and furosemide to manage the acute pulmonary edema and rapid ventricular response caused by decompensated mitral stenosis.
The correct management is the administration of intravenous metoprolol and furosemide. This patient's clinical presentation—rapidly progressive dyspnea, hemoptysis, and physical exam findings of a loud first heart sound, opening snap, and mid-diastolic rumble—is highly consistent with rheumatic mitral stenosis. The irregularly irregular rhythm and absent 'a' waves in the jugular venous pulse indicate new-onset atrial fibrillation. In patients with mitral stenosis, the fixed valve area means that left ventricular filling is highly dependent on the duration of diastole. The tachycardia associated with atrial fibrillation drastically shortens diastolic filling time, leading to a severe and rapid rise in left atrial pressure. In a pregnant patient, who already has a physiologic 40%40\% to 50%50\% increase in plasma volume, this acute rise in pressure immediately transmits to the pulmonary vasculature, causing flash pulmonary edema (manifesting as crackles, wheezing, and hypoxemia). Immediate management requires strict rate control to prolong diastole (using beta-blockers like metoprolol or non-dihydropyridine calcium channel blockers) and diuresis to reduce pulmonary congestion (using loop diuretics like furosemide).

Step-by-Step Solution

1
Identify the underlying valvular pathology from the physical examination.
The loud first heart sound, early diastolic high-frequency sound (opening snap), and low-pitched mid-diastolic murmur strongly indicate rheumatic mitral stenosis.
Recognizing the classic auscultatory findings of mitral stenosis is crucial for understanding the patient's hemodynamic compromise.
2
Determine the cause of the acute decompensation.
The irregularly irregular pulse with absent 'a' waves in the jugular venous pulse signifies new-onset atrial fibrillation.
Tachycardia in mitral stenosis drastically reduces diastolic filling time, causing blood to back up into the pulmonary circulation. This is exacerbated by the physiologic 40%40\% to 50%50\% plasma volume expansion of pregnancy.
3
Select the most appropriate pharmacologic intervention.
Intravenous beta-blockers (like metoprolol) are needed for rate control, and loop diuretics (like furosemide) are required to treat the pulmonary edema.
Slowing the heart rate increases diastolic filling time, directly reducing left atrial pressure, while diuresis effectively relieves the fluid overload.

Key Concept

Management of decompensated mitral stenosis with atrial fibrillation in pregnancy relies on strict rate control to prolong diastolic filling time and diuresis to relieve pulmonary congestion.
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Topics

Cardiovascular System

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