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Difficulty: EasyCardiovascular System

An emergency medical services team brings a 58-year-old man to the hospital due to severe, continuous substernal chest pain, shortness of breath, and profound diaphoresis that began 45 minutes ago. His medical history is significant for hyperlipidemia and a 35-pack-year smoking habit. Initial vital signs demonstrate a blood pressure of 85/50 mmHg85/50\text{ mmHg}, a heart rate of 55/min55/\text{min}, and a respiratory rate of 20/min20/\text{min}. Physical examination reveals significantly elevated jugular venous pressure, but the lung fields are completely clear to auscultation bilaterally. A 12-lead electrocardiogram demonstrates 3 mm3\text{ mm} ST-segment elevations in leads II, III, and aVF. Which of the following is the most appropriate next step in the management of this patient's hypotension?

  1. A
    Immediate transport for a computed tomography angiography of the chest
  2. B
    Administration of nebulized albuterol and intravenous corticosteroids
  3. Administration of an intravenous normal saline bolusAnswer
  4. D
    Administration of intravenous vancomycin and piperacillin-tazobactam
  5. E
    Withhold interventions until quantitative serum troponin levels are resulted

Answer

Administration of an intravenous normal saline bolus
The correct answer addresses the specific pathophysiology of a right ventricular (RV) infarction. This patient's electrocardiogram shows an inferior myocardial infarction (ST elevations in II, III, aVF), and the physical examination reveals elevated jugular venous pressure with clear lung fields. This triad is the classic presentation of an RV infarction. In this state, the right ventricle loses its contractility and becomes a passive conduit, making it highly dependent on adequate right-sided filling pressures (preload) to push blood into the left side of the heart. Consequently, the first-line therapy to correct the resulting hypotension is volume resuscitation with an intravenous normal saline bolus to maximize preload. Standard angina medications that reduce preload, such as nitroglycerin, must be strictly avoided as they can precipitate profound cardiovascular collapse.

Step-by-Step Solution

1
Analyze the electrocardiogram findings and initial vital signs.
ST-segment elevations in leads II, III, and aVF indicate an acute inferior myocardial infarction. The blood pressure is profoundly low (85/50 mmHg85/50\text{ mmHg}) accompanied by relative bradycardia.
Identifying the anatomical location of the infarction is critical to predicting and treating specific hemodynamic complications.
2
Correlate the physical examination findings with the type of infarction.
The combination of elevated jugular venous pressure and completely clear lungs in the setting of an inferior myocardial infarction points directly to right ventricular involvement.
Right ventricular infarction leads to poor forward flow to the left ventricle, causing systemic hypotension while keeping the pulmonary circulation free of edema.
3
Determine the optimal physiological intervention for the hypotension.
The infarcted right ventricle acts as a passive conduit and becomes highly dependent on elevated preload to maintain cardiac output, making intravenous fluids the necessary initial treatment.
Preload must be artificially supported with a normal saline bolus to push blood through the impaired right heart; conversely, preload-reducing agents must be strictly avoided.

Key Concept

The classic triad of an acute right ventricular infarction includes hypotension, elevated jugular venous pressure, and clear lung fields; the initial treatment of choice is optimizing preload with an intravenous normal saline bolus.
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Topics

Cardiovascular System

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