An emergency medical team evaluates a 65-year-old male who presents with the abrupt onset … — USMLE Step 3

An emergency medical team evaluates a $65$ -year-old male who presents with the abrupt onset of severe, sharp chest pain that radiates to his interscapular region. He describes the pain as a "tearing" sensation. His medical history is significant for poorly controlled essential hypertension and stage $4$ chronic kidney disease with a baseline serum creatinine of $3.4$ mg/dL. His temperature is $37.1^\circ$ C ( $98.8^\circ$ F), blood pressure is $192/114$ mm Hg in the right arm and $154/96$ mm Hg in the left arm, and heart rate is $105$ /min. Physical examination reveals a new diastolic decrescendo murmur at the right upper sternal border. An electrocardiogram shows left ventricular hypertrophy but no acute ST-segment changes. A chest radiograph demonstrates a widened mediastinum. Which of the following is the most appropriate next step in the diagnostic workup?

A
Computed tomography angiography of the chest
B
Coronary angiography
Transesophageal echocardiographyAnswer
D
Transthoracic echocardiography
E
Magnetic resonance angiography of the chest

Answer

Transesophageal echocardiography

The patient's clinical presentation—sudden, tearing chest pain radiating to the back, asymmetric blood pressures, and a new murmur of aortic regurgitation—is highly suspicious for an acute aortic dissection. In hemodynamically stable patients with normal renal function, computed tomography angiography (CTA) is the standard initial imaging modality. However, this patient has stage 4 chronic kidney disease, making the administration of iodinated contrast for a CTA contraindicated due to the high risk of contrast-induced nephropathy. Transesophageal echocardiography (TEE) is highly sensitive and specific for evaluating the thoracic aorta. It does not require intravenous contrast and can be performed rapidly, making it the most appropriate diagnostic choice in this specific clinical scenario.

Step-by-Step Solution

Identify the primary suspected diagnosis based on the clinical presentation.

The tearing chest pain radiating to the back, asymmetric upper extremity blood pressures, new aortic regurgitation murmur, and widened mediastinum strongly suggest an acute thoracic aortic dissection.

Recognizing the high-acuity diagnosis dictates the urgency and type of diagnostic imaging required.

Determine the standard first-line diagnostic test for the suspected condition and evaluate for any patient-specific contraindications.

Computed tomography angiography (CTA) is the standard initial test, but the patient's stage 4 chronic kidney disease (creatinine 3.4 mg/dL) is a strong contraindication to the required iodinated contrast.

Administering iodinated contrast to this patient carries an unacceptably high risk of irreversible contrast-induced nephropathy.

Select the most appropriate alternative diagnostic modality that balances diagnostic accuracy with patient safety.

Transesophageal echocardiography (TEE) is highly sensitive, avoids nephrotoxic contrast, and can be performed rapidly.

TEE provides the necessary anatomic visualization of the thoracic aorta without compromising the patient's remaining renal function.

Key Concept

In patients with suspected acute aortic dissection who have underlying severe renal impairment or hemodynamic instability, transesophageal echocardiography (TEE) is the preferred diagnostic imaging modality over computed tomography angiography (CTA).

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