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Difficulty: HardDiagnostic Workup and Test Sequencing

A 68-year-old man is brought to the emergency department via ambulance due to the sudden onset of severe, tearing chest pain that radiates to his back between his shoulder blades. The pain began abruptly 45 minutes ago while he was sitting at his desk. His medical history includes poorly controlled hypertension, type 2 diabetes mellitus, and stage IV chronic kidney disease. Current medications include amlodipine, lisinopril, insulin glargine, and aspirin.

Upon arrival, his temperature is 37.0°C (98.6°F), blood pressure is 185/105 mmHg in the right arm and 145/85 mmHg in the left arm. Pulse is 110/min, and respirations are 22/min. Oxygen saturation is 96% on room air. The patient appears distressed and diaphoretic. Cardiopulmonary examination reveals a regular tachycardia and a faint early diastolic murmur at the right upper sternal border. Lungs are clear to auscultation bilaterally. There is a noticeable discrepancy in radial pulse volume between the right and left arms.

Electrocardiography (ECG) shows sinus tachycardia with left ventricular hypertrophy but no acute ST-segment or T-wave changes. Initial laboratory studies reveal a serum creatinine of 2.8 mg/dL (baseline 2.5 mg/dL) and high-sensitivity troponin T within normal limits. Intravenous labetalol is initiated for blood pressure and heart rate control.

Which of the following is the most appropriate next step in the diagnostic workup?

  1. A
    Computed tomography angiography (CTA) of the chest
  2. B
    Transthoracic echocardiography (TTE)
  3. Transesophageal echocardiography (TEE)Answer
  4. D
    Magnetic resonance angiography (MRA) of the chest
  5. E
    Emergent coronary angiography

Answer

Transesophageal echocardiography (TEE)
The patient's clinical presentation (sudden tearing chest pain, pulse asymmetry, a blood pressure differential, and a new early diastolic murmur indicating aortic regurgitation) is highly suspicious for an acute thoracic aortic dissection. Rapid, definitive imaging is required to confirm the diagnosis and determine the anatomical extent (Type A versus Type B). The primary imaging modalities for confirming an aortic dissection are computed tomography angiography (CTA) and transesophageal echocardiography (TEE). While CTA is typically the preferred initial modality because it is fast and non-invasive, it requires iodinated contrast, which is strictly contraindicated in this patient due to his stage IV chronic kidney disease (creatinine 2.8 mg/dL). Therefore, TEE is the most appropriate diagnostic test. It provides excellent sensitivity and specificity for detecting an intimal flap, can evaluate for complications like pericardial effusion or aortic valve involvement, can be performed quickly at the bedside, and entirely avoids nephrotoxic contrast agents.

Step-by-Step Solution

1
Analyze the patient's clinical presentation and physical examination findings.
The patient exhibits sudden, severe, tearing chest pain radiating to the back, significant pulse and blood pressure asymmetry between his arms, and a new early diastolic murmur indicating aortic regurgitation.
Identifying this classic triad of symptoms establishes a highly elevated pre-test probability for an acute thoracic aortic dissection.
2
Evaluate the initial diagnostic data (ECG and laboratory results) to rule out immediate mimics and assess patient safety for imaging.
The ECG shows no acute ischemic changes, and troponin is normal, making an acute myocardial infarction less likely. Importantly, the serum creatinine is significantly elevated at 2.8 mg/dL.
Ruling out clear ST-elevation myocardial infarction prevents inappropriate antithrombotic therapy. Noting the severely impaired renal function is critical for selecting a safe imaging modality.
3
Determine the optimal diagnostic test based on patient-specific contraindications.
Computed tomography angiography (CTA) is contraindicated due to the patient's advanced chronic kidney disease. Transesophageal echocardiography (TEE) is selected instead.
TEE provides high diagnostic accuracy for identifying an intimal flap without the need for nephrotoxic iodinated contrast material, and it can be performed quickly in hemodynamically unstable or critically ill patients.

Key Concept

In patients with a high clinical suspicion for acute thoracic aortic dissection who have severe renal impairment (preventing the use of iodinated contrast) or hemodynamic instability, transesophageal echocardiography (TEE) is the diagnostic imaging modality of choice.
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Diagnostic Workup and Test Sequencing

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