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Difficulty: HardCardiovascular System

A 62-year-old man is brought to the emergency department by ambulance after experiencing sudden-onset, severe epigastric and lower chest pain for the past 90 minutes. He describes the pain as a "heavy weight" and reports associated nausea and profuse sweating. His medical history includes type 2 diabetes mellitus, peripheral arterial disease, and a 40-pack-year smoking history. Current medications include metformin and atorvastatin. On arrival, his temperature is 36.8 °C (98.2 °F), blood pressure is 82/50 mmHg, pulse is 112/min, and respiratory rate is 18/min. Pulse oximetry is 97% on room air. Physical examination reveals clear lungs to auscultation bilaterally. Jugular venous pulsations are visible 10 cm above the sternal angle while the patient is seated at a 45-degree angle. Cardiac auscultation reveals a regular rhythm without murmurs or gallops. The extremities are cool and clammy. An electrocardiogram reveals sinus tachycardia with 3-mm ST-segment elevations in leads II, III, and aVF, as well as 2-mm ST-segment depressions in leads I and aVL. The patient is administered chewable aspirin and ticagrelor. Which of the following is the most appropriate initial step to stabilize this patient's hemodynamics?

  1. Administration of an isotonic saline bolusAnswer
  2. B
    Administration of sublingual nitroglycerin
  3. C
    Administration of intravenous furosemide
  4. D
    Administration of intravenous metoprolol
  5. E
    Initiation of an intravenous dobutamine infusion

Answer

Administration of an isotonic saline bolus
This patient is presenting with an acute inferior ST-segment elevation myocardial infarction (STEMI) complicated by right ventricular myocardial infarction (RVMI). The classic triad of RVMI includes hypotension, clear lungs (no evidence of pulmonary edema), and elevated jugular venous pressure. In RVMI, the right ventricle loses its contractile function and acts largely as a passive conduit. Consequently, the right ventricle becomes highly dependent on elevated venous return (preload) to push blood through the pulmonary circuit and ensure adequate filling of the left ventricle. Therefore, the most appropriate initial step to stabilize hemodynamics in a patient with RVMI is volume expansion with an isotonic saline bolus. This optimizes right ventricular preload and improves systemic cardiac output.

Step-by-Step Solution

1
Analyze the electrocardiogram and clinical presentation to determine the anatomical location of the myocardial infarction.
ST-segment elevations in leads II, III, and aVF indicate an acute inferior ST-segment elevation myocardial infarction (STEMI).
Identifying the territory of the infarct is crucial for predicting potential complications, such as right ventricular involvement.
2
Synthesize the vital signs and physical examination findings to diagnose the specific complication.
The classic triad of hypotension, clear lungs, and elevated jugular venous pressure in the setting of an inferior STEMI confirms right ventricular myocardial infarction (RVMI).
The right coronary artery supplies the inferior wall of the left ventricle and the right ventricle. Obstruction leads to right ventricular failure.
3
Select the appropriate targeted intervention to address the altered hemodynamics of right ventricular failure.
Choose volume expansion with an isotonic saline bolus to maximize venous return.
The infarcted right ventricle loses contractility and becomes highly dependent on elevated preload to push blood forward into the pulmonary circulation and maintain left ventricular filling.

Key Concept

Hemodynamic management of Right Ventricular Myocardial Infarction
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Topics

Cardiovascular System

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