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A 68-year-old man is admitted to the intensive care unit with an acute exacerbation of heart failure. On hospital day 3, he experiences sudden-onset right-sided pleuritic chest pain and worsening dyspnea. His temperature is 37.1°C (98.8°F), blood pressure is 115/75 mm Hg, pulse is 118/min, and respiratory rate is 24/min. Oxygen saturation is 88% on 4 L/min via nasal cannula, decreased from 95% on 2 L/min yesterday. Physical examination reveals elevated jugular venous pressure, bilateral basilar crackles, and bilateral 2+ pitting edema extending to the knees. The right calf appears slightly more swollen than the left.

Laboratory studies:
Serum creatinine: 3.4 mg/dL (baseline 1.2 mg/dL)
Brain natriuretic peptide: 1,800 pg/mL

ECG shows sinus tachycardia and new T-wave inversions in leads V1-V4. A portable chest radiograph reveals bilateral pleural effusions and prominent interstitial markings consistent with pulmonary edema. The clinical team suspects an acute pulmonary embolism. Which of the following is the most appropriate next imaging study to evaluate for suspected pulmonary embolism in this patient?

  1. A
    Computed tomography pulmonary angiography
  2. B
    Ventilation-perfusion (V/Q) scanning
  3. C
    Transthoracic echocardiography
  4. D
    Magnetic resonance angiography of the chest
  5. Lower extremity compression ultrasonographyCevap

Cevap

Lower extremity compression ultrasonography is the most appropriate next step.
The correct answer identifies the optimal alternative diagnostic strategy when standard PE imaging pathways are blocked. CT pulmonary angiography is contraindicated due to the patient's severe acute kidney injury. The primary alternative, a ventilation-perfusion (V/Q) scan, is heavily compromised by the patient's severe pulmonary edema and bilateral pleural effusions, which would likely result in an indeterminate reading. In patients with a high pretest probability for PE who cannot undergo definitive chest imaging, lower extremity compression ultrasonography is the preferred next step. Finding a deep vein thrombosis (especially given the asymmetric calf swelling) confirms the presence of venous thromboembolism and dictates the same management as a PE (therapeutic anticoagulation), eliminating the immediate need for potentially harmful or inconclusive chest imaging.

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1
Assess the pretest probability of pulmonary embolism (PE) and identify the standard diagnostic imaging.
The patient has a high clinical suspicion for an acute PE based on symptoms, tachycardia, and hypoxia. Computed tomography pulmonary angiography (CTPA) is typically the initial diagnostic test of choice.
CTPA provides rapid and definitive visualization of the pulmonary vasculature.
2
Evaluate for contraindications to the standard imaging modality.
The patient has developed severe acute kidney injury (creatinine 3.4 mg/dL), which serves as a major contraindication to the iodinated contrast required for CTPA.
Administering iodinated contrast in this setting poses a high risk of exacerbating the acute kidney injury.
3
Determine the viability of standard alternative chest imaging modalities.
A ventilation-perfusion (V/Q) scan is typically the next best alternative; however, it is likely to be non-diagnostic in this patient due to the concurrent pulmonary edema and pleural effusions noted on the chest radiograph.
An abnormal chest radiograph significantly reduces the diagnostic accuracy of a V/Q scan because alveolar filling and pleural fluid obscure the typical mismatched perfusion defects.
4
Select the safest, most effective alternative diagnostic pathway.
Lower extremity compression ultrasonography should be performed next.
Diagnosing a deep vein thrombosis (DVT) confirms venous thromboembolism. Because the treatment (therapeutic anticoagulation) is the same for DVT and PE, a positive ultrasound provides actionable data without exposing the patient to contrast or radiation, and circumvents the limitations of a V/Q scan.

Anahtar Kavram

Diagnostic approach to suspected pulmonary embolism when standard imaging is contraindicated.
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