If a pulmonary embolism is not treated promptly, what proportion of patients may die?

• A. About one quarter
• B. About one third
• C. About one half
• D. About three quarters

Answer: (B)

When a pulmonary embolism is not treated promptly, the clot can block a large portion of the pulmonary arteries, causing a sudden rise in right heart workload, impaired oxygenation, and potential shock or cardiac arrest. This risk of rapid deterioration translates into a mortality rate around one third, reflecting the natural history of untreated emboli, especially when they are large or cause hemodynamic instability. Prompt treatment with anticoagulation, and in the most severe cases thrombolysis or surgical embolectomy, substantially improves survival. Smaller, less extensive emboli carry a lower risk, which is why the mortality figure is described as about one third in general terms.