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Difficulty: HardCardiovascular System

Paramedics evaluate a 61-year-old male at his residence following an emergency call for sudden-onset, excruciating retrosternal chest pain that radiates to his mid-back. He is immediately transported to the nearest tertiary care center. On arrival, the patient is visibly distressed, diaphoretic, and tachypneic. His medical history is notable for uncontrolled hypertension and a 40-pack-year smoking history. Vital signs demonstrate a temperature of 36.8°C (98.2°F), a heart rate of 122/min, a blood pressure of 78/46 mm Hg in the right arm and 82/48 mm Hg in the left arm, and an oxygen saturation of 88% on room air. Physical examination reveals elevated jugular venous pressure and diffuse bilateral crackles on lung auscultation. A bounding, early diastolic decrescendo murmur is auscultated along the right sternal border. An electrocardiogram reveals sinus tachycardia with left ventricular hypertrophy but no acute ischemic ST-segment changes. Which of the following is the most appropriate next step in the management of this patient?

  1. A
    Computed tomography angiography of the chest and abdomen
  2. B
    Initiation of an intravenous labetalol infusion
  3. Bedside transesophageal echocardiographyAnswer
  4. D
    Administration of intravenous loop diuretics and continuous positive airway pressure
  5. E
    Therapeutic anticoagulation with intravenous unfractionated heparin

Answer

The correct answer is bedside transesophageal echocardiography.
The correct answer proposes utilizing a bedside imaging modality. This patient's presentation of tearing chest and back pain, combined with a new early diastolic decrescendo murmur and flash pulmonary edema, is highly indicative of a Type A aortic dissection complicated by acute aortic regurgitation. The retrograde propagation of the intimal flap into the aortic root disrupts the commissural support of the aortic valve leaflets, leading to sudden, massive regurgitation. Because the left ventricle has not had time to undergo eccentric hypertrophy to accommodate this sudden volume load, end-diastolic pressure rises exponentially, backing up into the pulmonary circulation (causing bilateral crackles and hypoxemia) and severely reducing forward cardiac output (causing profound hypotension and shock). In a hemodynamically unstable patient, leaving the emergency department or intensive care unit for a computed tomography (CT) scan is strictly contraindicated. Bedside transesophageal echocardiography (TEE) is the diagnostic procedure of choice; it offers excellent sensitivity and specificity for visualizing the proximal aorta, identifying the intimal flap, and evaluating the mechanism of aortic regurgitation, all while allowing concurrent resuscitation or immediate transition to the operating room.

Step-by-Step Solution

1
Analyze the patient's presenting symptoms and history.
Sudden, excruciating tearing chest pain radiating to the back in a patient with chronic hypertension.
These are the classic hallmark symptoms of an acute aortic dissection.
2
Evaluate the patient's vital signs and physical examination findings.
Severe hypotension (BP 78/46 mm Hg), tachycardia, hypoxemia, bilateral pulmonary crackles, elevated JVP, and a new early diastolic decrescendo murmur at the right sternal border.
These findings indicate that the dissection has extended proximally to involve the aortic root, causing failure of aortic valve coaptation and resulting in acute aortic regurgitation (AR). The unacclimated left ventricle cannot handle the sudden volume load, rapidly leading to flash pulmonary edema and cardiogenic shock.
3
Determine the safest diagnostic approach for a hemodynamically unstable patient.
Select bedside transesophageal echocardiography (TEE) over computed tomography (CT) angiography.
CT angiography requires transporting the patient out of the resuscitation area and placing them supine, which is highly dangerous in severe shock. TEE can be performed immediately at the bedside (or in the operating room prior to sternotomy) with high sensitivity and specificity for visualizing the aortic root and assessing valvular function.

Key Concept

In patients with suspected acute aortic dissection who are hemodynamically unstable, bedside transesophageal echocardiography (TEE) is the initial diagnostic modality of choice to avoid the risks associated with transport to a CT scanner.
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Topics

Cardiovascular System

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