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Difficulty: MediumCardiovascular System

A 6060-year-old male is transported to the emergency department by ambulance following an abrupt onset of severe dyspnea that started 22 hours ago. He has a known medical history of essential hypertension and mitral valve prolapse. He reports no recent febrile illness, chills, or changes in sputum. His temperature is 37.0∘37.0^\circ C (98.6∘98.6^\circ F), blood pressure is 165/95165/95 mmHg, heart rate is 118118/min, respiratory rate is 2828/min, and oxygen saturation is 85%85\% on room air. He is visibly distressed and using accessory muscles of respiration. Jugular venous distention is noted at 88 cm H 2_2 O. Lung auscultation reveals diffuse bilateral crackles extending up to the apices, accompanied by prominent expiratory wheezing. Cardiac auscultation demonstrates a regular tachycardia with a normal S 11 and a harsh holosystolic murmur heard best at the apex that radiates to the axilla.

Laboratory results are as follows:
- Leukocyte count: 8,5008,500/mm 3^3
- Thyroid-stimulating hormone (TSH): 0.10.1 μ\mu U/mL (Normal: 0.4−4.00.4-4.0 μ\mu U/mL)
- Free thyroxine (T4): 1.21.2 ng/dL (Normal: 0.8−1.80.8-1.8 ng/dL)
- Arterial blood gas (room air): pH 7.287.28, pCO 2_2 5555 mmHg, pO 2_2 5050 mmHg, HCO 3−_3^- 2525 mEq/L

Chest radiography reveals bilateral alveolar opacities with a normal-sized cardiac silhouette.

Which of the following is the most appropriate initial pharmacologic intervention for this patient's underlying condition?

  1. Intravenous sodium nitroprussideAnswer
  2. B
    Inhaled albuterol and oral prednisone
  3. C
    Intravenous piperacillin-tazobactam
  4. D
    Intravenous sodium bicarbonate
  5. E
    Oral methimazole

Answer

Intravenous sodium nitroprusside
The correct intervention is intravenous sodium nitroprusside. This patient's presentation of abrupt-onset severe dyspnea, flash pulmonary edema, and a harsh holosystolic murmur radiating to the axilla in the setting of mitral valve prolapse is highly characteristic of acute mitral regurgitation (MR), likely secondary to ruptured chordae tendineae. In acute MR, the sudden massive volume load on an unprepared left atrium leads to rapidly elevated pulmonary venous pressures and acute pulmonary edema. The chest radiograph typically shows bilateral infiltrates with a normal cardiac silhouette because the left atrium has not had time to undergo compensatory dilation. In a hemodynamically stable or hypertensive patient with acute MR, the immediate goal is afterload reduction. Sodium nitroprusside, a potent rapid-acting arterial vasodilator, decreases systemic vascular resistance. This promotes forward stroke volume into the aorta and significantly reduces the regurgitant fraction back into the left atrium, effectively relieving pulmonary congestion while awaiting definitive surgical intervention.

Step-by-Step Solution

1
Identify the primary pathology based on the physical exam and imaging findings.
The patient has a new harsh holosystolic murmur radiating to the axilla, flash pulmonary edema, and a normal-sized heart on chest X-ray, which strongly indicates acute mitral regurgitation.
Accurately diagnosing the cause of sudden cardiogenic shock and respiratory failure is required to guide specific therapy.
2
Determine the hemodynamic goals for acute mitral regurgitation.
The immediate goal is to decrease systemic vascular resistance (afterload) to promote forward blood flow and reduce the regurgitant volume into the left atrium.
High systemic resistance exacerbates the backflow of blood into the low-pressure left atrium, worsening pulmonary congestion.
3
Select the appropriate pharmacologic agent to achieve this hemodynamic goal.
Intravenous sodium nitroprusside is selected.
It is a potent arterial and venous vasodilator that rapidly reduces afterload in a hypertensive patient, directly targeting the pathophysiologic derangement.

Key Concept

Hemodynamic management of acute mitral regurgitation
Estimated Time:1m 30s
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Topics

Cardiovascular System

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