Background: The contemporary natural history of patients with acute pulmonary embolism (PE) not receiving (or early discontinuing) anticoagulant therapy has not been consistently evaluated.
Objective: To assess the rate of the composite outcome of PE-related death, sudden death, or recurrent thromboembolism (VTE) within 30 days in all PE patients in whom anticoagulation was not administered or discontinued prematurely (<90 days of anticoagulation).
Methods: We used the RIETE database to assess the incidence rates (per 100 person-days) of the composite outcome within the subsequent 30 days. The risk of these events was compared to PE patients who were anticoagulated for ≥90 days.
Results: Of 34,447 PE recruited from 2001 to 2017, 47 (0.14%) did not receive anticoagulants and 1348 (3.91%) discontinued it before 90 days. Fatal PE developed in 25 (53%) of those without any anticoagulation and in 45 (3.33%) with premature discontinuations. Sudden death or non-fatal recurrent VTE occurred in 6 (0.45%) and 24 (1.48%) patients, respectively. The incidence of the primary outcome declined logarithmically from 6.36 per 100 patient-days in untreated patients to 0.32-0.13 in those treated for 8-90 days. During the first week of follow-up, the incidence rate was 13.9 and 0.60-0.31 per 100 patient-days, respectively. The adjusted odds of the primary outcome was 27 fold higher in untreated than in treated patients, and progressively decreased to 2.5-7 fold higher in patients treated for at least 7 days.
Conclusion: The incidence of the composite outcome was highest during the first week, and inversely and logarithmically correlated with the duration of anticoagulant therapy.
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