What is the risk of pulmonary embolism (PE) in a 24-week pregnant woman with symptoms of intermittent dyspnea, tachycardia, and chest heaviness?

Risk of Pulmonary Embolism in a 24-Week Pregnant Woman with Intermittent Dyspnea, Tachycardia, and Chest Heaviness

This patient requires formal diagnostic evaluation for PE, as pulmonary embolism is the leading cause of pregnancy-related maternal death in developed countries, and her symptoms—while potentially physiological—cannot be dismissed without objective testing. 1

Understanding the Clinical Context

Why This Presentation Demands Attention

• PE accounts for 20% of maternal deaths in the United States, with an incidence of 1 per 1,000 to 1 per 3,000 deliveries. 1, 2
• Pregnancy creates a hypercoagulable state through increased coagulation factors, venous stasis from uterine compression, and vascular changes—fulfilling Virchow's triad. 3, 4
• The symptoms described (dyspnea, tachycardia, chest heaviness) overlap significantly with normal physiological changes of pregnancy, making clinical diagnosis extremely challenging. 1, 5

The Diagnostic Dilemma

• Breathlessness is common in normal pregnancy, which is why the 2014 ESC Guidelines explicitly state this symptom "should be interpreted with caution" in pregnant women. 1
• However, the risk of missing PE far outweighs concerns about unnecessary testing—erroneously missing PE leads to maternal death, while erroneously diagnosing it exposes the patient to anticoagulation risks and impacts future pregnancy management. 1
• Most pregnant women investigated for suspected PE do not have the disease (low prevalence among those tested), but this should not deter appropriate evaluation. 5, 6

Specific Risk Assessment Approach

Clinical Features That Increase PE Likelihood

• Tachycardia and chest heaviness are concerning features that warrant investigation, even though tachycardia can be physiological in pregnancy. 2, 6
• The presence of multiple risk factors or smoking significantly increases PE probability. 6
• Unilateral leg swelling would substantially elevate concern for deep vein thrombosis (DVT) and associated PE. 2, 3

Clinical Features That Lower PE Likelihood

• The absence of pleuritic chest pain has a negative predictive value of 97.8% in pregnant women, though this patient has "chest heaviness" which is non-specific. 6
• A Wells score <6 points may help stratify risk, though validation data in pregnancy are limited. 1

Recommended Diagnostic Algorithm

Step 1: Initial Assessment

• Perform bilateral lower extremity compression ultrasonography FIRST if any signs or symptoms of DVT are present (leg swelling, pain, warmth). 1, 3
• If DVT is confirmed, start anticoagulation immediately—no further radiation-based testing is needed, as treatment is identical. 1, 3

Step 2: D-Dimer Consideration

• D-dimer measurement should be considered to rule out PE, but with critical caveats. 1
• A normal D-dimer has the same exclusion value as in non-pregnant patients, but is found less commonly because D-dimer physiologically increases throughout pregnancy. 1
• Recent evidence shows D-dimer has inadequate sensitivity (73%) and poor specificity (15%) in pregnancy, so it cannot be relied upon alone. 2, 7
• If D-dimer is normal AND clinical probability is low, PE can be safely excluded without imaging in select cases. 5

Step 3: Imaging When Indicated

If lower extremity ultrasound is negative or not indicated, and D-dimer is elevated or not performed:

• Obtain a chest X-ray first. 3, 7
• If chest X-ray is normal, perfusion scintigraphy is preferred to minimize maternal breast radiation exposure. 1, 3
• If chest X-ray is abnormal, CT pulmonary angiography (CTPA) should be performed as the first-line option. 1, 3
• Both modalities are safe—all diagnostic tests deliver radiation doses well below the 50 mSv (50,000 mGy) threshold for fetal harm. 1, 7

Critical Pitfalls to Avoid

Do Not Dismiss Symptoms as "Normal Pregnancy Changes"

• While dyspnea and tachycardia are common in pregnancy, they can also indicate PE—formal diagnostic assessment with validated methods is mandatory when PE is suspected. 1, 2
• The intermittent nature of symptoms does not exclude PE. 8

Do Not Let Radiation Concerns Prevent Necessary Testing

• Chest X-ray delivers <0.01 mGy to the fetus—approximately 1/5,000,000th of the safety threshold. 7
• CTPA and perfusion scans deliver doses well below 50 mSv, and the danger threshold for fetal injury is 50,000 mGy. 1, 7
• The hazards of missing a potentially fatal diagnosis far outweigh radiation concerns, particularly for suspected high-risk PE. 1, 7
• Iodinated contrast agents for CTPA are not associated with neonatal adverse events. 8

Do Not Rely Solely on D-Dimer

• D-dimer alone should not be used to exclude PE in pregnancy due to inadequate sensitivity and specificity. 2, 7
• D-dimer is most useful when combined with clinical prediction rules (revised Geneva score or pregnancy-adapted YEARS algorithm). 8, 5

Do Not Delay Arterial Blood Gas Measurement

• If arterial blood gas is obtained, draw blood with the patient in the upright position—partial pressure of oxygen may be falsely lower in the supine position during the third trimester. 1

When to Escalate Care Immediately

The following features indicate high-risk PE requiring urgent multidisciplinary involvement:

• Severe dyspnea at rest, syncope, hemoptysis, or unexplained hypotension. 3
• Oxygen desaturation (SpO2 <95%), persistent tachycardia, or abnormal lung auscultation. 3
• Cardiac arrest or hemodynamic instability—consider thrombolysis or surgical thrombectomy despite bleeding risks. 1

Bottom Line for This Patient

Given the symptoms of intermittent dyspnea, tachycardia, and chest heaviness at 24 weeks gestation, this patient cannot be reassured without objective testing. 1 Begin with bilateral lower extremity compression ultrasonography if any leg symptoms are present; otherwise, proceed with D-dimer measurement (recognizing its limitations) and chest X-ray to guide further imaging with either perfusion scintigraphy or CTPA. 1, 3 The goal is diagnostic certainty—missing PE in pregnancy is potentially fatal, while radiation exposure from appropriate testing poses negligible fetal risk. 1, 7