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Difficulty: HardCardiovascular System

A 59-year-old male is brought to the emergency department by his spouse due to the sudden onset of crushing substernal chest pain that began 1 hour ago. He also reports profound weakness and diaphoresis. His medical history is significant for type 2 diabetes mellitus and hypertension. His current temperature is 37.1°C (98.8°F), blood pressure is 80/50 mmHg, heart rate is 110/min, and respiratory rate is 20/min. Pulse oximetry shows 95% on room air. On physical examination, the patient appears pale and diaphoretic. Jugular venous pulsation is visible 8 cm above the sternal angle. The lungs are clear to auscultation bilaterally with no wheezes or crackles. Cardiac auscultation reveals a regular tachycardia with no murmurs, rubs, or gallops. The extremities are cool and clammy with delayed capillary refill. Laboratory studies show a serum bicarbonate of 18 mEq/L and a lactate level of 4.5 mmol/L. An ECG reveals 3-mm ST-segment elevations in leads II, III, and aVF, as well as reciprocal ST-segment depressions in leads I and aVL. Which of the following is the most appropriate next step in the management of this patient's hemodynamic instability?

  1. Intravenous isotonic saline bolusAnswer
  2. B
    Intravenous furosemide therapy
  3. C
    Immediate computed tomography angiography of the chest
  4. D
    Empiric administration of broad-spectrum intravenous antibiotics
  5. E
    Intravenous sodium bicarbonate infusion

Answer

Intravenous isotonic saline bolus
The correct answer is the administration of an intravenous isotonic saline bolus. This patient is presenting with an acute inferior myocardial infarction complicated by right ventricular (RV) infarction. This diagnosis is characterized by the classic clinical triad of hypotension, elevated jugular venous pressure, and clear lungs on auscultation, alongside ST-segment elevations in leads II, III, and aVF. Because the ischemic right ventricle loses its ability to contract effectively, it acts essentially as a passive conduit. Therefore, the heart becomes highly dependent on adequate right-sided filling pressures (preload) to drive blood through the pulmonary circulation and into the left ventricle. Maximizing preload with intravenous fluids is the critical first step to restoring cardiac output and reversing the cardiogenic shock.

Step-by-Step Solution

1
Analyze the patient's presenting hemodynamics and physical exam findings.
The patient exhibits profound hypotension, elevated jugular venous pressure, and clear lung fields.
This specific triad suggests isolated right-sided heart failure without left-sided fluid backup (pulmonary edema).
2
Correlate the physical exam with the diagnostic ECG findings.
The ECG shows an acute inferior STEMI (elevations in II, III, aVF).
Inferior myocardial infarctions frequently involve the right ventricle, structurally confirming the cause of the right-sided failure.
3
Determine the appropriate physiological intervention for right ventricular ischemia.
Administer an intravenous isotonic saline bolus.
An infarcted right ventricle loses contractility and relies entirely on elevated venous filling pressures (preload) to push blood into the pulmonary circulation and maintain left-sided cardiac output.

Key Concept

Acute right ventricular myocardial infarction typically presents with hypotension, elevated jugular venous pressure, and clear lungs. It is highly preload-dependent, making intravenous fluid resuscitation the initial treatment of choice, while preload-reducing agents (e.g., diuretics, nitrates) are strictly contraindicated.
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Topics

Cardiovascular System

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