Pulmonary Embolism MCQ — NEET PG Practice Question | NEETPGAI
Pulmonary Embolism
easy
microscope Pathology
What is the most common source of pulmonary embolism in clinical practice?
A. Right atrial thrombus
B. Deep vein thrombosis of the lower limbs
C. Paradoxical embolism from the left atrium
D. Tumor embolism from lung malignancy
Explanation
Source of Pulmonary Embolism
Key Point
Deep vein thrombosis (DVT) of the lower extremities accounts for approximately 90–95% of clinically significant pulmonary emboli. The thrombus dislodges and travels via the inferior vena cava to the right heart and lodges in the pulmonary arteries.
Pathophysiology of PE Origin
The vast majority of PE arise from venous thromboembolism (VTE) in the deep veins of the legs:
Table
Source
Frequency
Clinical Significance
Lower limb DVT
90–95%
Most common; often asymptomatic until PE occurs
Right atrial thrombus
1–2%
Rare; associated with central lines, arrhythmias
Paradoxical embolism
<1%
Requires PFO or ASD; venous thrombus crosses to systemic circulation
Tumor embolism
<1%
Seen in advanced malignancy; usually with other emboli
High-YieldNEET PG
The popliteal vein and above (iliofemoral and popliteal veins) are the primary sites of DVT that lead to PE. Calf vein thrombi rarely cause clinically significant PE unless they propagate proximally.
Clinical Pearl
Approximately 50% of patients with proximal DVT have asymptomatic PE on imaging, and conversely, 30–40% of patients presenting with PE have no clinical evidence of DVT on examination—emphasizing that DVT may be "silent" before PE manifests.
Why Lower Limb DVT Dominates
1.
Anatomical factors: The lower limbs are dependent, with slow venous return and high hydrostatic pressure.
2.
Virchow's triad: Venous stasis (immobility, surgery), endothelial injury (trauma, lines), and hypercoagulability (malignancy, thrombophilia) are common in the legs.
3.
Thrombus size: Lower limb thrombi are large enough to cause hemodynamically significant PE.
Mnemonic
DVT-PE axis — Deep Vein Thrombosis (legs) → Pulmonary Embolism (lungs). This is the cardinal pathway in >90% of cases.
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