In a 47-year-old woman with a mildly elevated D-dimer, a negative lower‑extremity duplex ultrasound, and an echocardiogram showing mild right ventricular enlargement, what is the appropriate next step in evaluating for pulmonary embolism?

Proceed Directly to CT Pulmonary Angiography (CTPA)

In a 47-year-old woman with mildly elevated D-dimer, negative lower extremity ultrasound, and echocardiogram showing mild right ventricular enlargement, you should proceed directly to CT pulmonary angiography to definitively diagnose or exclude pulmonary embolism. The combination of elevated D-dimer and RV enlargement on echo significantly elevates her clinical probability of PE, making imaging mandatory regardless of the negative leg ultrasound 1, 2.

Why CTPA is Required

The echocardiographic finding of mild RV enlargement is a critical piece of evidence that fundamentally changes the diagnostic approach:

• RV enlargement indicates hemodynamic impact from potential PE, even if the patient appears clinically stable 1
• This finding, combined with elevated D-dimer, creates an intermediate-to-high clinical probability scenario where imaging cannot be safely deferred 2
• The negative lower extremity duplex does not exclude PE - only 30-50% of PE patients have detectable DVT, and PE can occur without any leg clot 3, 4

The Diagnostic Algorithm in This Scenario

Step 1: Clinical Probability Assessment

• Elevated D-dimer + RV enlargement on echo = intermediate or high clinical probability
• At age 47, even using age-adjusted D-dimer threshold (470 ng/mL), a "mildly elevated" value warrants imaging 2

Step 2: D-dimer Interpretation

• D-dimer should not be used to exclude PE when clinical probability is elevated 2
• The presence of RV changes elevates the pretest probability beyond what D-dimer can safely rule out 1

Step 3: Imaging Decision

• CTPA is the definitive test and should be performed without delay 2, 5, 3
• Ventilation-perfusion scanning is an alternative only if CTPA is contraindicated (contrast allergy, renal failure) 2, 3

Critical Pitfalls to Avoid

Do not be falsely reassured by:

• The negative leg ultrasound - PE exists independently in 50-70% of cases 3
• "Mild" RV enlargement - any RV dysfunction suggests significant clot burden 1
• Only "mildly" elevated D-dimer - the absolute value matters less than the clinical context at this probability level 6, 7

Do not order additional D-dimer testing - you already have an elevated value with concerning echo findings, making repeat testing unnecessary and potentially harmful through delay 2

The Evidence Hierarchy

The European Society of Cardiology guidelines explicitly state that in patients with RV overload on echocardiography, multidetector CT should be performed to confirm PE diagnosis 1. The American College of Physicians reinforces that imaging with CTPA is indicated in patients with high pretest probability, and your patient's echo findings place her in this category 2.

More recent evidence from 2019 ESC guidelines confirms that CTPA showing segmental or more proximal filling defects in patients with intermediate or high clinical probability is diagnostic and requires no further testing 4.

Practical Next Steps

1. Order CTPA immediately - specify "CT pulmonary angiography for suspected PE"
2. Initiate anticoagulation while awaiting imaging if no contraindications exist, given the intermediate-high probability 4
3. Assess for contraindications to contrast (renal function, prior reactions) - if present, proceed to V/Q scan 2, 3

The combination of elevated D-dimer and RV enlargement creates a clinical scenario where the risk of missing PE far outweighs the risks of CTPA imaging 1, 2, 4.