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Difficulty: MediumOrdering Imaging Studies

A 65-year-old man is brought to the emergency department via ambulance due to sudden, severe, and tearing chest pain that radiates directly to his back between the shoulder blades. The pain began 45 minutes ago while he was resting. His medical history is significant for poorly controlled hypertension, type 2 diabetes mellitus, and stage 4 chronic kidney disease. Upon arrival, he appears in acute distress. His temperature is 37.1°C (98.8°F), blood pressure is 195/110 mm Hg in the right arm and 175/95 mm Hg in the left arm, pulse is 112/min, and respirations are 22/min. Physical examination reveals a new early diastolic decrescendo murmur heard best at the right upper sternal border. The lungs are clear to auscultation bilaterally. Neurologic examination shows no focal deficits. Laboratory studies demonstrate a serum creatinine level of 3.6 mg/dL (baseline 2.9 mg/dL) and a blood urea nitrogen of 48 mg/dL. An electrocardiogram shows left ventricular hypertrophy and sinus tachycardia, but no acute ischemic changes. A portable chest radiograph reveals a widened mediastinum. Which of the following is the most appropriate next step in imaging for this patient?

  1. Transesophageal echocardiographyAnswer
  2. B
    Computed tomography angiography of the chest
  3. C
    Magnetic resonance angiography of the chest
  4. D
    Transthoracic echocardiography
  5. E
    Non-contrast computed tomography of the chest

Answer

Transesophageal echocardiography
The patient's classic presentation (tearing chest pain, unequal blood pressures, new diastolic murmur, widened mediastinum) strongly suggests an acute aortic dissection. To definitively diagnose a dissection, imaging of the entire aorta is required. The most accurate imaging studies are computed tomography angiography (CTA), transesophageal echocardiography (TEE), and magnetic resonance angiography (MRA). Because this patient has significant renal failure (creatinine 3.6 mg/dL), the iodinated contrast required for a CTA is contraindicated. MRA is inappropriate in an acute emergency because it is time-consuming and its gadolinium contrast poses a risk for nephrogenic systemic fibrosis in severe renal disease. Therefore, TEE is the most appropriate next step because it has excellent sensitivity and specificity for aortic dissection, uses no contrast, and can be rapidly performed at the bedside.

Step-by-Step Solution

1
Analyze the patient's presentation.
The patient has tearing chest pain radiating to the back, asymmetric blood pressures, a new murmur of aortic regurgitation, and a widened mediastinum.
These findings are highly suspicious for an acute aortic dissection.
2
Evaluate the patient's comorbidities and laboratory results.
The patient has underlying stage 4 chronic kidney disease with an acute elevation in serum creatinine (3.6 mg/dL).
Severe renal dysfunction dictates which imaging modalities are safe, as certain contrast agents are contraindicated.
3
Select the optimal imaging modality.
Transesophageal echocardiography is chosen over computed tomography angiography.
Transesophageal echocardiography has high sensitivity and specificity for aortic dissection, avoids nephrotoxic iodinated contrast, and can be rapidly performed in acute settings.

Key Concept

In patients with suspected acute aortic dissection who have severe renal dysfunction or hemodynamic instability, transesophageal echocardiography is the preferred diagnostic imaging modality over computed tomography angiography.
Estimated Time:1m 30s
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Ordering Imaging Studies

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