In a patient presenting with acute dyspnea, pleuritic chest pain, tachycardia, tachypnea, hypoxemia, recent risk factors for venous thromboembolism (e.g., recent surgery, immobilization, active cancer, prior deep‑vein thrombosis, hormonal therapy), and an electrocardiogram (ECG) showing sinus tachycardia with right‑sided strain, what is the most likely diagnosis and what immediate management steps should be taken?

Diagnosis: Acute Pulmonary Embolism

In a patient presenting with acute dyspnea, pleuritic chest pain, tachycardia, tachypnea, hypoxemia, VTE risk factors, and ECG showing sinus tachycardia with right-sided strain, the most likely diagnosis is acute pulmonary embolism, and you should immediately initiate therapeutic anticoagulation with unfractionated heparin (80 units/kg IV bolus) while simultaneously pursuing diagnostic confirmation with CT pulmonary angiography. 1, 2

Immediate Management Steps

1. Assess Hemodynamic Status First

• Check for shock or hypotension (systolic BP <90 mmHg or drop ≥40 mmHg lasting >15 minutes) to determine if this is high-risk PE requiring emergent reperfusion therapy 1
• If hemodynamically unstable, perform bedside transthoracic echocardiography immediately to assess for right ventricular dysfunction and acute pulmonary hypertension 1
• In a critically unstable patient with echocardiographic evidence of RV overload, thrombolytic therapy may be initiated based solely on echocardiographic findings without waiting for CT confirmation 1, 2

2. Start Anticoagulation Immediately (Do Not Wait for Imaging)

• Initiate unfractionated heparin 80 units/kg IV bolus immediately based on high clinical suspicion before diagnostic confirmation 2, 3, 4
• UFH is preferred over low-molecular-weight heparin in this presentation because the patient has signs suggesting possible massive PE (right-sided strain on ECG), where rapid reversal may be required 2
• This immediate anticoagulation reduces early mortality even before the diagnosis is definitively confirmed 2, 3

3. Obtain CT Pulmonary Angiography Within 1 Hour

• CT pulmonary angiography is the first-line diagnostic test for hemodynamically stable patients and should be performed within 1 hour for suspected massive PE 1, 2
• A positive CTPA showing segmental or more proximal filling defects confirms the diagnosis 2
• If the patient is too unstable to leave the bedside, echocardiographic evidence of RV dysfunction is sufficient to proceed with reperfusion therapy 1

Clinical Probability Assessment

Your patient has high clinical probability based on:

• Dyspnea and tachypnea (present in >90% of PE cases; their absence virtually excludes PE) 1, 2
• Pleuritic chest pain (occurs in 52% of PE cases, caused by pleural irritation from distal emboli) 1, 5
• Tachycardia (present in 26% of cases) 5
• Hypoxemia (present in 75% of cases, though 20% may have normal oxygen levels) 1, 5
• Multiple VTE risk factors (recent surgery, immobilization, active cancer, prior DVT, hormonal therapy—risk factors are present in 80-90% of PE patients) 1, 2
• ECG showing right-sided strain (RV strain pattern has 97.4% specificity for PE with OR 4.58; S1Q3T3, right bundle branch block, or T-wave inversion in V1-V4 suggest more severe PE) 1, 6

Why Skip D-Dimer Testing

• Do not order D-dimer in this patient because high clinical probability makes a negative D-dimer insufficient to exclude PE (low negative predictive value) 1, 2
• D-dimer should only be used in low or intermediate probability patients to avoid unnecessary imaging 1, 2
• Proceed directly to CTPA in high-probability patients 2

Alternative Diagnostic Considerations

If CTPA is Contraindicated or Unavailable

• Perform lower-extremity compression ultrasound if the patient has clinical signs of DVT; finding proximal DVT confirms venous thromboembolism and justifies anticoagulation without pulmonary imaging 1, 2
• Use ventilation-perfusion (V/Q) scanning if CTPA is contraindicated (renal failure, contrast allergy, pregnancy), but only if chest X-ray is normal and no significant cardiopulmonary disease exists 2
• A normal perfusion scan excludes PE; a high-probability V/Q scan with high clinical probability confirms PE 1, 2

If Patient Stabilizes After Initial Management

• Once hemodynamically stable, obtain definitive diagnosis with CTPA even if thrombolysis was started based on echocardiography alone 1
• A normal CTPA or lung scan in the setting of suspected massive PE should prompt investigation for alternative causes of shock (acute coronary syndrome, aortic dissection, tamponade, acute valvular dysfunction) 1

Common Pitfalls to Avoid

• Do not delay anticoagulation while waiting for imaging—failure to start heparin immediately in high-probability patients significantly increases VTE episodes and sudden cardiac death at 3 months 1
• Do not rely on normal oxygen saturation to rule out PE; up to 40% of PE patients have normal SaO₂ 2, 5
• Do not order D-dimer in high-probability patients or hospitalized patients with comorbidities (infection, cancer, inflammation, recent surgery) due to high false-positive rates 2
• Do not use V/Q scanning if chest X-ray is abnormal or the patient has chronic cardiopulmonary disease, as results will likely be non-diagnostic 2
• Do not assume a normal ECG excludes PE; 20-25% of PE patients, including those with large clot burden, have completely normal ECGs 6

Risk Stratification After Diagnosis

• High-risk PE (shock/hypotension): Consider thrombolysis or embolectomy 1
• Intermediate-risk PE (RV dysfunction on echo or CT, elevated troponin/BNP, but hemodynamically stable): Close monitoring, consider escalation if deterioration 1
• Low-risk PE (no RV dysfunction, hemodynamically stable): Standard anticoagulation alone 1