Can Anticoagulants Prevent Pulmonary Embolism 100 Percent?
No, anticoagulants cannot prevent pulmonary embolism 100 percent—they reduce the risk of recurrent venous thromboembolism by approximately 90% during active treatment, but do not eliminate the risk entirely. 1
Efficacy During Active Treatment
Indefinite anticoagulation reduces recurrent VTE risk by about 90% compared to placebo, but this benefit is partially offset by bleeding complications. 1
Extended oral anticoagulant treatment reduces the risk for recurrent VTE by less than 90%, meaning at least 10% of patients may still experience recurrence despite continuous therapy. 1
Anticoagulants are highly effective in preventing recurrent VTE during active treatment, but they do not eliminate the risk of subsequent recurrence after treatment discontinuation. 1
Risk After Discontinuation
After stopping anticoagulation, the risk of recurrence returns to baseline levels regardless of whether treatment was stopped after 3,6, or 12 months. 1
For unprovoked PE, the annual recurrence rate after stopping anticoagulation exceeds 8% per year in high-risk patients (those with active cancer, autoimmune disease, antiphospholipid syndrome, or prior unprovoked VTE). 1
In patients with cancer-associated thrombosis, the recurrence rate reaches approximately 20% during the first 12 months after the index event, even with anticoagulation. 1
Bleeding Risk Trade-off
The major bleeding risk during oral anticoagulant therapy is approximately 3% per year with an annual case fatality rate of 0.6%. 1
At an annual VTE recurrence rate of 12%, the risk of death from recurrent thromboembolism is balanced by the risk of death from anticoagulant-related bleeding. 1
Direct oral anticoagulants (DOACs) have similar efficacy to vitamin K antagonists in reducing VTE risk but with lower overall and intracranial bleeding rates, though possibly higher gastrointestinal bleeding with dabigatran, edoxaban, and rivaroxaban. 1
Clinical Implications
The decision for extended anticoagulation represents a balance between the estimated risk of recurrence after treatment discontinuation and the risk of bleeding complications during treatment. 1
For PE secondary to a major transient/reversible risk factor (surgery, trauma, hospitalization), anticoagulation for 3 months is recommended, after which the recurrence risk is low (<3% per year). 1
For unprovoked PE or PE with persistent risk factors, extended or indefinite anticoagulation should be considered in patients with low bleeding risk. 1
Common Pitfalls
Assuming that longer initial treatment duration (beyond 3 months) will reduce long-term recurrence risk after stopping anticoagulation—this is incorrect, as recurrence risk returns to baseline regardless of initial treatment duration. 1
Failing to recognize that in patients with prior PE, recurrent VTE more frequently manifests as PE (rather than DVT), with a case fatality rate twice as high as recurrence after DVT alone. 1
Underestimating the persistent recurrence risk in cancer patients, who require indefinite anticoagulation due to cancer outweighing all other patient-related risks. 1