A 67-year-old woman is evaluated in the cardiac intensive care unit after a sudden episode… — USMLE Step 2 CK

A $67$ -year-old woman is evaluated in the cardiac intensive care unit after a sudden episode of unresponsiveness. She was admitted $4$ days ago for an acute anterior ST-segment elevation myocardial infarction and underwent successful percutaneous coronary intervention of the left anterior descending artery. Her medical history is notable for hypertension, type 2 diabetes mellitus, and a $40$ -pack-year smoking history. Following the episode of unresponsiveness, she quickly regains consciousness but reports feeling extremely weak and lightheaded. Her temperature is $36.7^\circ\text{C}$ ( $98.1^\circ\text{F}$ ), blood pressure is $72/40$ mm Hg, pulse is $126$ /min and regular, and respirations are $26$ /min. Pulse oximetry is $93\%$ on room air. Physical examination reveals cold, clammy extremities and significant jugular venous distention. The apical impulse is not palpable. Lung fields are clear to auscultation bilaterally. Heart sounds are distant, and no murmurs, rubs, or gallops are appreciated. An electrocardiogram shows sinus tachycardia and persistent ST-segment elevations in the anterior leads, unchanged from the post-intervention electrocardiogram. Arterial blood gas analysis on room air reveals a pH of $7.24$ , pCO $_2$ of $32$ mm Hg, and pO $_2$ of $68$ mm Hg. Which of the following is the most appropriate next step in the management of this patient?

Perform immediate bedside echocardiographyAnswer
B
Administer inhaled albuterol and intravenous methylprednisolone
C
Administer intravenous sodium bicarbonate
D
Transport the patient for computed tomography angiography of the chest
E
Initiate empiric therapy with intravenous broad-spectrum antibiotics

Answer

Perform immediate bedside echocardiography

The patient's presentation of sudden-onset shock, elevated jugular venous pressure, clear lung fields, and muffled heart sounds

4

days after an anterior myocardial infarction is classic for left ventricular free wall rupture leading to cardiac tamponade. Bedside echocardiography is the diagnostic test of choice to rapidly confirm the presence of a pericardial effusion and right ventricular diastolic collapse in a hemodynamically unstable patient, which can then be immediately followed by pericardiocentesis or surgical repair.

Step-by-Step Solution

Analyze the patient's hemodynamic status and physical exam findings.

The patient is in profound shock (blood pressure

72/40

mm Hg) with Beck's triad: hypotension, jugular venous distention, and distant heart sounds.

Identifying the type of shock is critical. Clear lungs rule out cardiogenic shock from left ventricular failure, pointing toward obstructive shock.

Correlate the physical findings with the clinical timeline.

The presentation occurs exactly

4

days after an acute anterior myocardial infarction.

The

3

5

day post-infarction window is the peak time for macrophage-mediated structural degradation, making left ventricular free wall rupture highly likely.

Determine the safest and most effective diagnostic modality.

Bedside echocardiography is selected.

The patient is hemodynamically unstable, absolutely contraindicating transport to a CT scanner. Bedside ultrasound rapidly and safely confirms cardiac tamponade.

Key Concept

Recognition and acute management of left ventricular free wall rupture leading to cardiac tamponade post-myocardial infarction.

Estimated Time:1m 30s

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