What is the best next step in care for a patient with chest pain, shortness of breath, tachycardia, and hypoxemia?

Best Next Step: Obtain CT Pulmonary Angiogram

This patient requires immediate CT pulmonary angiography (CTPA) to diagnose pulmonary embolism, which is highly suspected based on her clinical presentation. 1

Clinical Reasoning

This patient presents with a high clinical probability of pulmonary embolism based on multiple critical features:

• Major risk factor present: Oral contraceptive use (a well-established thrombotic risk factor) 1
• Classic PE triad: Unexplained dyspnea, chest pain, and tachycardia 1
• Objective hemodynamic instability: Tachycardia (HR 115), tachypnea (RR 22), hypoxemia (SpO2 92%), and low-grade fever 1
• Clinical DVT: Unilateral leg swelling strongly suggests concurrent deep vein thrombosis 1
• Decreased breath sounds: Suggests pulmonary pathology consistent with PE 1

Why CTPA is the Correct Answer

CT angiography with contrast is the preferred gold standard imaging modality for PE diagnosis and should be performed immediately in this high-probability patient. 1, 2

Advantages of CTPA in this case:

• Directly visualizes pulmonary emboli as filling defects in pulmonary arteries 2
• Can assess RV strain, which helps risk-stratify the patient 1
• Evaluates alternative diagnoses that may cause similar symptoms 1, 3
• Can be combined with indirect CT venography to detect concurrent DVT 1

Why Other Options Are Incorrect

D-dimer is NOT appropriate here:

• D-dimer should NOT be performed when clinical probability is high 1
• The British Thoracic Society explicitly states: "It should not be performed if clinical probability is high" 1
• D-dimer has limited utility in patients on oral contraceptives due to baseline elevation 1
• Only negative D-dimer results are clinically useful for excluding PE in LOW probability patients 1
• This patient's high pretest probability (oral contraceptives + tachypnea + hypoxemia + clinical DVT) makes D-dimer testing inappropriate and potentially dangerous by delaying definitive imaging 1

Antibiotics are incorrect:

• While the patient has low-grade fever, the clinical picture strongly suggests PE, not pneumonia 1
• Unilateral leg swelling and hypoxemia with clear lung fields (except decreased breath sounds) are not consistent with bacterial pneumonia 1

Discharge with albuterol is dangerous:

• This patient has hemodynamic instability with hypoxemia and tachycardia, making discharge inappropriate 1
• The presentation suggests life-threatening PE, not reactive airway disease 1

Critical Management Points

Consider initiating anticoagulation immediately while awaiting CTPA results if there are no contraindications, as recommended by NCCN guidelines: "In cases with high suspicion of PE and no contraindications, consider initiating early anticoagulation while waiting for imaging results." 1

Additional immediate workup should include:

• ECG to exclude acute MI and assess for RV strain patterns 1, 4
• Troponin and NT-proBNP for risk stratification 1
• CBC, PT/aPTT, renal function before anticoagulation 1

Common pitfall to avoid:

Do not delay imaging to obtain D-dimer in high-probability patients. The British Thoracic Society emphasizes that most patients with PE are breathless and/or tachypneic >20/min, and when combined with major risk factors (like oral contraceptives), clinical probability is HIGH, making D-dimer testing both inappropriate and potentially harmful. 1