A 70-year-old man with a history of chronic obstructive pulmonary disease (COPD) and hyper… — USMLE Step 2 CK

A $70$ -year-old man with a history of chronic obstructive pulmonary disease (COPD) and hypertension is brought to the emergency department by ambulance due to the sudden onset of severe substernal chest pressure, shortness of breath, and diaphoresis that began $45\text{ minutes}$ ago. Upon arrival, his blood pressure is $85/54\text{ mmHg}$ , heart rate is $108\text{/min}$ , and respiratory rate is $22\text{/min}$ . Pulse oximetry is $94\%$ on room air. Physical examination reveals elevated jugular venous pressure with prominent $x$ and $y$ descents. Lung auscultation is clear bilaterally with mildly prolonged expiration but no wheezes or crackles. A $12$ -lead electrocardiogram demonstrates $3\text{ mm}$ ST-segment elevations in leads II, III, and aVF, with reciprocal ST-segment depressions in leads I and aVL.

In addition to preparation for emergent percutaneous coronary intervention, what is the most appropriate initial step in the management of this patient?

A
Intravenous furosemide
B
Sublingual nitroglycerin
Intravenous normal saline bolusAnswer
D
Inhaled albuterol and systemic corticosteroids
E
Noninvasive positive pressure ventilation

Answer

Intravenous normal saline bolus

The correct answer is an intravenous normal saline bolus. This patient's electrocardiogram shows an acute inferior wall myocardial infarction (ST elevations in leads II, III, and aVF). The accompanying clinical triad of hypotension, elevated jugular venous pressure, and clear lung fields strongly suggests a right ventricular (RV) infarction, which complicates up to 50% of inferior myocardial infarctions. The ischemic right ventricle has significantly impaired contractility and becomes highly dependent on elevated preload to maintain forward flow through the pulmonary circulation to the left ventricle. Therefore, the most appropriate initial management for hypotension in the setting of an RV infarction is volume expansion with intravenous isotonic fluids (e.g., normal saline) to maximize the Starling mechanism and improve cardiac output.

Step-by-Step Solution

Analyze the patient's clinical presentation and electrocardiogram (ECG) findings.

The patient exhibits hypotension, elevated jugular venous pressure, clear lung fields, and ST-segment elevations in inferior leads (II, III, and aVF).

Identifying the classic clinical triad combined with inferior ECG changes is essential to diagnose an acute right ventricular (RV) myocardial infarction.

Determine the pathophysiologic state of the right ventricle in this condition.

The ischemic right ventricle loses its contractility and becomes highly dependent on elevated right-sided filling pressures (preload).

Understanding RV preload dependence is crucial for selecting the correct hemodynamic intervention and avoiding fatal medication errors.

Select the appropriate initial management for the patient's hypotension.

Intravenous fluid resuscitation (e.g., normal saline) is indicated.

Increasing preload maximizes the Starling mechanism, thereby maintaining forward blood flow through the pulmonary circulation to the left ventricle and improving systemic blood pressure.

Key Concept

Right ventricular myocardial infarction presents with the triad of hypotension, elevated jugular venous pressure, and clear lungs. It is a highly preload-dependent state that requires intravenous fluid resuscitation; preload-reducing therapies must be strictly avoided.

Estimated Time:1m 15s

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