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Difficulty: Very hardDiagnostic Workup and Test Sequencing

A 72-year-old woman is brought to the emergency department by ambulance after suddenly collapsing at home. Her husband reports that she complained of sharp, right-sided chest pain and extreme shortness of breath immediately before losing consciousness. She has a history of hormone receptor-positive breast cancer currently treated with tamoxifen, as well as essential hypertension. Upon arrival, she is poorly responsive, diaphoretic, and in visible respiratory distress. Vital signs are temperature 37.1°C (98.8°F), blood pressure 76/50 mm Hg, heart rate 132/min, respiratory rate 30/min, and oxygen saturation 85% on 15 L/min via a non-rebreather mask. Physical examination reveals elevated jugular venous pressure. Lungs are clear to auscultation bilaterally. Cardiac auscultation reveals a rapid rhythm with a loud P2 and no murmurs. An electrocardiogram demonstrates sinus tachycardia, right axis deviation, and inverted T waves in leads V1 through V4. A portable chest radiograph shows clear lung fields and a normal cardiac silhouette. What is the most appropriate next step in the diagnostic workup?

  1. Bedside transthoracic echocardiographyAnswer
  2. B
    Computed tomography pulmonary angiography
  3. C
    Measurement of high-sensitivity cardiac troponin and brain natriuretic peptide
  4. D
    Transesophageal echocardiography
  5. E
    Bilateral lower extremity compression ultrasonography

Answer

Bedside transthoracic echocardiography is the most appropriate next diagnostic step to rapidly evaluate for right ventricular dysfunction in a hemodynamically unstable patient.
This patient presents with obstructive shock, highly suggestive of a massive pulmonary embolism (PE) given her acute dyspnea, chest pain, profound hypotension, and significant risk factors (malignancy and tamoxifen use). Her electrocardiogram demonstrates acute right heart strain (S1Q3T3 equivalent with right axis deviation and anterior T-wave inversions), further supporting the diagnosis. The definitive diagnostic test for PE is typically computed tomography pulmonary angiography (CTPA). However, a critical inflection point in the diagnostic algorithm for PE is hemodynamic stability. Transporting a hemodynamically unstable patient out of the resuscitation bay to a CT scanner poses an unacceptable risk of cardiopulmonary arrest in an unmonitored setting away from immediate life-saving interventions. Therefore, the most appropriate next step in the diagnostic workup is bedside transthoracic echocardiography (TTE). TTE can be performed immediately and can reveal indirect signs of massive PE, such as right ventricular dilation, septal flattening (D-sign), and right ventricular free wall hypokinesis with apical sparing (McConnell's sign). In a crashing patient with high pretest probability, echocardiographic evidence of right ventricular overload provides sufficient diagnostic justification to proceed directly to life-saving reperfusion therapy, such as systemic thrombolysis or surgical embolectomy, while simultaneously ruling out other catastrophic causes of shock like pericardial tamponade.

Step-by-Step Solution

1
Assess the patient's hemodynamic stability and acuity.
The patient is in profound shock (blood pressure 76/50 mm Hg) with severe hypoxia.
Hemodynamic instability dictates whether the patient can safely leave the emergency department for diagnostic imaging.
2
Formulate the most likely differential diagnosis.
The patient has obstructive shock, most likely due to a massive pulmonary embolism given her risk factors (malignancy, tamoxifen) and presentation (acute right heart strain on ECG, clear lungs).
Identifying the suspected etiology guides the selection of targeted, high-yield diagnostic tests.
3
Select the appropriate diagnostic testing pathway based on stability.
Bedside transthoracic echocardiography is chosen over computed tomography pulmonary angiography.
Transporting an unstable patient carries an unacceptable risk of cardiac arrest; bedside imaging provides immediate evidence of right ventricular overload to justify emergent reperfusion therapy.

Key Concept

In hemodynamically unstable patients with high clinical suspicion for massive pulmonary embolism, bedside transthoracic echocardiography is the diagnostic test of choice to identify right ventricular strain, as transporting the patient for computed tomography carries an unacceptably high mortality risk.
Estimated Time:2m 0s
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Diagnostic Workup and Test Sequencing

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