Massive Pulmonary Embolism
The most probable cause of death in this 70-year-old man is massive pulmonary embolism (PE) despite the normal duplex scan, given the sudden PEA arrest without chest pain or dyspnea—a presentation highly characteristic of fatal PE.
Clinical Reasoning
The clinical scenario strongly points to massive PE based on several key factors:
Why PE Despite Normal Duplex?
- Duplex ultrasound has significant limitations: A normal lower extremity duplex does not exclude PE. The ESC guidelines explicitly state that if proximal compression ultrasound (CUS) is negative, further testing is needed to confirm or exclude PE 1
- Emboli may have already migrated: The calf pain suggests a DVT that may have completely embolized to the pulmonary circulation before the duplex was performed, leaving no residual thrombus in the leg veins
- Distal DVT may be missed: Standard duplex often focuses on proximal veins and may miss distal calf vein thrombosis, which can still embolize
Why PEA Arrest Points to Massive PE
The presentation of witnessed PEA arrest is pathognomonic for massive PE:
- Research evidence is compelling: In a medical examiner study of 384 sudden death cases, PE was the second most common cause of cardiac arrest (9.6%). Critically, among 52 patients with primary PEA, 28 (53%) died from massive PE 2
- Witnessed arrest + primary PEA = high probability: The combination of witnessed arrest and primary PEA generated a 57% post-test probability of massive PE with 67.6% sensitivity and 94.5% specificity 2
- PEA is the characteristic arrest rhythm: Non-shockable rhythms (asystole and PEA) account for 88.88% of cardiac arrest deaths, with PEA being particularly associated with PE 3
Why No Chest Pain or Dyspnea?
This absence of classic symptoms actually supports massive PE:
- Sudden massive obstruction: When a large embolus acutely obstructs the main pulmonary arteries, cardiovascular collapse can occur within seconds to minutes, before the patient develops or reports respiratory symptoms
- Rapid progression: The timeline described—"few minutes" from ER arrival to PEA arrest—is consistent with acute massive PE causing sudden right ventricular failure and obstructive shock
- Silent presentation is documented: Case reports confirm that PE can present with altered consciousness or sudden collapse without preceding dyspnea 4
Alternative Diagnoses (Less Likely)
While other causes of PEA exist, they are less consistent with this presentation:
- Cardiac tamponade: Would typically have preceding symptoms or trauma history
- Tension pneumothorax: Would require mechanism of injury or underlying lung disease
- Hyperkalemia: Would need renal failure or medication history
- Acute MI: Usually presents with chest pain, though silent MI possible in elderly
Clinical Pitfall
The critical error here was accepting the negative duplex as excluding venous thromboembolism. According to ESC guidelines, when clinical suspicion for PE exists (calf pain in this case), a negative proximal CUS should prompt further testing—not reassurance 1. The appropriate next step would have been D-dimer testing (if not already elevated) or direct CTPA imaging given the clinical concern.
Diagnostic Approach That Should Have Been Followed
Based on ESC 2019 guidelines 1:
- Clinical suspicion of PE (calf pain) → Should not be dismissed by negative duplex alone
- Risk stratification needed: Even with negative leg ultrasound, PE assessment should continue
- CTPA is the gold standard: Should have been performed given clinical suspicion
- Point-of-care ultrasound during arrest: Could have shown RV dysfunction, supporting PE diagnosis in real-time 1
The combination of calf pain, normal duplex, and witnessed PEA arrest creates a clinical picture where massive PE is the most likely diagnosis, representing a case where the embolus had already migrated centrally before imaging could detect the source.