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Difficulty: HardOrdering Imaging Studies

A 68-year-old man presents to the emergency department complaining of sudden-onset, severe, "tearing" chest pain that radiates to between his shoulder blades. He has a history of poorly controlled hypertension and type 2 diabetes mellitus complicated by diabetic nephropathy. His current medications include amlodipine, lisinopril, and insulin glargine.

Blood pressure is 172/96 mmHg in the right arm and 148/88 mmHg in the left arm. Heart rate is 92/min, and respiratory rate is 18/min. Physical examination reveals a new early diastolic murmur heard best at the right sternal border.

Laboratory testing shows a serum creatinine of 3.4 mg/dL3.4 \text{ mg/dL} (baseline 3.1 mg/dL3.1 \text{ mg/dL}) and an estimated glomerular filtration rate of 17 mL/min/1.73m217 \text{ mL/min/1.73m}^2. An electrocardiogram shows left ventricular hypertrophy without acute ischemic changes. A portable chest radiograph demonstrates a widened mediastinum.

Which of the following is the most appropriate next step in imaging to confirm the diagnosis?

  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
    Conventional thoracic aortography

Answer

Transesophageal echocardiography is the most appropriate next imaging study, as it provides definitive diagnosis without exposing the patient to contraindicated contrast agents.
The clinical presentation (sudden tearing chest pain radiating to the back, asymmetric arm blood pressures, new diastolic murmur, and widened mediastinum) is classic for an acute aortic dissection. To definitively establish the diagnosis, imaging must clearly delineate the aortic anatomy and locate the intimal flap. While computed tomography angiography is often the initial test of choice due to its speed and widespread availability, it requires iodinated contrast, which is absolutely contraindicated in this patient given his estimated glomerular filtration rate of 17 mL/min/1.73m². Magnetic resonance angiography is similarly contraindicated because gadolinium exposure in severe renal impairment carries a black-box warning for nephrogenic systemic fibrosis. Transesophageal echocardiography circumvents these issues; it does not require intravenous contrast, can be rapidly deployed at the bedside, and provides excellent visualization of the thoracic aorta (particularly the ascending segment and aortic valve), making it the most appropriate choice.

Step-by-Step Solution

1
Identify the primary suspected diagnosis based on the clinical presentation.
The patient's sudden tearing chest pain, asymmetric blood pressures, new early diastolic murmur (aortic regurgitation), and widened mediastinum are highly suggestive of an acute thoracic aortic dissection.
Establishing the pretest probability of the disease dictates the need for definitive confirmatory imaging.
2
Evaluate the patient's baseline physiological parameters and comorbidities for imaging contraindications.
The patient has severe renal impairment, with an estimated glomerular filtration rate (eGFR) of 17 mL/min/1.73m².
Renal function directly determines whether nephrotoxic contrast (iodine) or renally cleared contrast (gadolinium) can be safely administered.
3
Select the imaging modality that provides high diagnostic accuracy while avoiding contraindicated agents.
Transesophageal echocardiography is selected.
It offers excellent sensitivity and specificity for detecting intimal flaps in the thoracic aorta and can be performed rapidly at the bedside without requiring intravenous contrast.

Key Concept

In patients with suspected acute aortic dissection who have severe renal impairment or hemodynamic instability, transesophageal echocardiography is the imaging modality of choice to avoid the nephrotoxic effects of iodinated contrast and the risk of nephrogenic systemic fibrosis from gadolinium.
Estimated Time:1m 30s
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Ordering Imaging Studies

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