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Difficulty: MediumInterpreting Imaging Results

A rapid response team is activated for a hospitalized patient in their late sixties who experiences sudden-onset severe dyspnea and syncope on the third day following a total knee arthroplasty. Current vital signs reveal a blood pressure of 78/50 mm Hg, heart rate of 124/min, and oxygen saturation of 86% on high-flow oxygen. Physical examination shows pronounced jugular venous distension. Lungs are clear to auscultation bilaterally. Stat laboratory testing reveals a troponin T level of 0.08 ng/mL (normal <0.04 ng/mL). A bedside point-of-care transthoracic echocardiogram is immediately performed and demonstrates a markedly dilated right ventricle. There is severe hypokinesis of the right ventricular mid-free wall, but the right ventricular apex exhibits normal contractility. Based on these sonographic findings, which of the following is the most likely diagnosis?

  1. Acute massive pulmonary embolismAnswer
  2. B
    Right ventricular myocardial infarction
  3. C
    Cardiac tamponade
  4. D
    Tension pneumothorax
  5. E
    Acute aortic dissection

Answer

Acute massive pulmonary embolism
The correct diagnosis relies heavily on the interpretation of the point-of-care echocardiogram. The patient is exhibiting signs of obstructive shock. The echocardiogram reveals right ventricular dilation with akinesia of the mid-free wall but normal apical contractility. This specific sonographic pattern is known as McConnell's sign and is highly indicative of an acute massive pulmonary embolism. The right ventricle bulges into the relatively lower pressure apex, preserving its motion while the free wall fails against acutely elevated pulmonary vascular resistance. The mild troponin elevation is secondary to right ventricular strain, and the recent joint replacement is a classic risk factor for venous thromboembolism.

Step-by-Step Solution

1
Identify the clinical syndrome
The patient is experiencing obstructive shock (hypotension, tachycardia, hypoxia, jugular venous distension) in a high-risk postoperative setting.
Establishing the type of shock narrows the differential diagnosis.
2
Evaluate the laboratory findings
The mildly elevated troponin indicates myocardial strain but is not highly specific for a primary coronary event in this context.
Troponin leak can occur secondary to severe right heart strain.
3
Interpret the imaging findings
The echocardiogram shows right ventricular dilation with mid-free wall akinesia and apical sparing (McConnell's sign).
This specific sonographic pattern is highly sensitive and specific for acute massive pulmonary embolism.

Key Concept

Echocardiographic interpretation of McConnell's sign (right ventricular mid-free wall hypokinesis with apical sparing) as a specific indicator of acute massive pulmonary embolism in the setting of obstructive shock.
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Interpreting Imaging Results

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