Emergency medical services transport a 62-year-old male patient to the acute care unit due… — USMLE Step 2 CK

Emergency medical services transport a $62$ -year-old male patient to the acute care unit due to two hours of unrelenting, oppressive chest discomfort that radiates to his jaw. He also reports profound diaphoresis and severe lightheadedness. His medical background includes type 2 diabetes mellitus, hyperlipidemia, and a $40$ -pack-year smoking history. Upon arrival, his temperature is $36.8^\circ\text{C}$ ( $98.2^\circ\text{F}$ ), his blood pressure is remarkably low at $82/52\text{ mm Hg}$ , pulse is $52\text{ beats/min}$ , and respirations are $18\text{ breaths/min}$ . Pulse oximetry reveals an oxygen saturation of $96\%$ on room air. Physical evaluation shows prominent jugular venous pulsations at $10\text{ cm}$ above the sternal angle while seated at $45$ degrees. Pulmonary auscultation indicates completely clear breath sounds bilaterally without any wheezes or crackles. The cardiac exam reveals a regular bradycardic rhythm with a right-sided S3 gallop, but no significant murmurs. An electrocardiogram is rapidly acquired and demonstrates $3\text{ mm}$ ST-segment elevations in leads II, III, and aVF, along with 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?

Intravenous administration of 0.9% sodium chlorideCevap
B
Sublingual administration of nitroglycerin
C
Intravenous administration of furosemide
D
Intravenous administration of metoprolol
E
Administration of nebulized albuterol and ipratropium

Cevap

The most appropriate next step is the intravenous administration of 0.9% sodium chloride.

The patient's presentation of hypotension, elevated jugular venous pressure, and clear lungs in the setting of an inferior STEMI (ST elevations in II, III, aVF) is the classic triad for a right ventricular (RV) infarction. The ischemic right ventricle loses contractility and becomes stiff, relying heavily on increased right atrial pressure (preload) to maintain flow through the pulmonary vasculature and fill the left ventricle. Therefore, the most appropriate immediate management to stabilize the patient's hemodynamics is volume expansion with intravenous isotonic saline (0.9% sodium chloride).

Adım Adım Çözüm

Analyze the electrocardiogram findings.

The ECG reveals ST-segment elevations in leads II, III, and aVF, diagnosing an acute inferior myocardial infarction.

Identifying the territory of the infarction is critical because inferior MIs commonly involve the right ventricle.

Correlate the ECG findings with the physical examination.

The triad of hypotension, elevated jugular venous pressure, and clear lung fields in the setting of an inferior STEMI is highly specific for right ventricular infarction.

Physical signs help distinguish right ventricular failure (systemic congestion, clear lungs) from left ventricular failure (pulmonary edema).

Determine the hemodynamic requirements of an infarcted right ventricle.

An ischemic right ventricle acts as a passive conduit and loses its contractile force, relying almost entirely on elevated venous pressure (preload) to push blood through the pulmonary circulation into the left heart.

Understanding the pathophysiology dictates that preload must be maximized and negative inotropes/venodilators must be avoided.

Select the appropriate pharmacological intervention.

Intravenous fluid resuscitation with isotonic saline is selected.

Volume expansion increases right ventricular preload, which enhances left ventricular filling and subsequently improves systemic cardiac output and blood pressure.

Anahtar Kavram

Management of right ventricular myocardial infarction requires avoiding preload-reducing agents and administering intravenous fluids to optimize right ventricular filling and cardiac output.

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