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Difficulty: MediumCardiovascular System

Paramedics transport a 5858-year-old male to the emergency department following the acute onset of unrelenting retrosternal chest pressure and profound diaphoresis that began 9090 minutes ago. On evaluation, his blood pressure is 82/5282/52 mmHg and his pulse is 5252/min. His respiratory rate is 1616/min and oxygen saturation is 96%96\% on room air. Physical examination demonstrates visibly distended neck veins while the patient is sitting at a 45∘45^\circ angle. Auscultation reveals clear lung fields bilaterally without crackles or wheezing. Cardiac examination demonstrates a regular, slow rhythm without murmurs, rubs, or gallops. A 12-lead electrocardiogram obtained by triage staff demonstrates 33-mm convex ST-segment elevations in leads II, III, and aVF, with reciprocal ST-segment depressions in leads I and aVL. In addition to antiplatelet therapy and preparation for immediate revascularization, which of the following is the most appropriate initial intervention to stabilize this patient's hemodynamics?

  1. Rapid infusion of isotonic crystalloid solutionAnswer
  2. B
    Sublingual isosorbide dinitrate
  3. C
    Intravenous loop diuretic administration
  4. D
    Urgent computed tomography angiography of the chest
  5. E
    Intravenous beta-adrenergic antagonist administration

Answer

The correct answer is the rapid infusion of isotonic crystalloid solution.
The patient is experiencing an acute inferior ST-segment elevation myocardial infarction (STEMI) complicated by right ventricular (RV) infarction. This complication is classically characterized by the physical exam triad of severe hypotension, elevated jugular venous pressure, and clear lung fields. Because the ischemic right ventricle loses its active pumping capability, it functions as a passive conduit. Maintaining forward blood flow through the pulmonary circulation and into the left ventricle becomes strictly dependent on adequate venous return (preload). Therefore, the most appropriate initial step to manage this patient's severe hypotension is volume loading with an isotonic crystalloid solution to maximize right-sided filling pressures and restore cardiac output.

Step-by-Step Solution

1
Analyze the electrocardiogram (ECG) findings in the context of the patient's presentation.
The presence of ST-segment elevations in leads II, III, and aVF identifies an acute inferior wall myocardial infarction.
Inferior wall MIs are frequently associated with proximal occlusion of the right coronary artery, which also supplies the right ventricle.
2
Correlate the ECG diagnosis with the physical examination findings.
The patient exhibits the classic triad of right ventricular (RV) infarction: hypotension, elevated jugular venous pressure (distended neck veins), and clear lung fields.
This triad confirms significant ischemic dysfunction of the right ventricle, distinguishing it from isolated left ventricular failure (which would present with pulmonary crackles).
3
Determine the hemodynamic requirements of an ischemic right ventricle.
The infarcted RV loses its contractile force, rendering it highly dependent on high venous filling pressures (preload) to push blood through the pulmonary circulation into the left heart.
Without adequate preload, left ventricular filling drops precipitously, leading to profound systemic hypotension and cardiogenic shock.
4
Select the appropriate pharmacologic intervention.
Administer an intravenous bolus of isotonic crystalloid solution (e.g., normal saline).
Volume expansion mechanically increases right-sided filling pressures, thereby optimizing Starling forces, restoring left ventricular preload, and improving systemic blood pressure.

Key Concept

Hemodynamic management of acute right ventricular myocardial infarction
Estimated Time:1m 30s
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Topics

Cardiovascular System

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