Impact of time in therapeutic range (TTR) within the first 72 h on prognosis in patients with pulmonary embolism treated with unfractionated heparin.

Pulmonary embolism (PE) is a life-threatening condition often treated with unfractionated heparin (UFH) in intermediate high-risk patients. Activated Partial Thromboplastin Time (aPTT) is used to monitor UFH efficacy. We sought to evaluate the correlation between time in therapeutic range (TTR) and prognosis in patients with pulmonary embolism treated with unfractionated heparin. A prospective cohort study included 203 patients admitted to a tertiary care center between July 2019 and August 2024 with a confirmed diagnosis of intermediate risk PE treated with UFH. TTR was calculated based on aPTT values during the first 72 h of hospitalization. The correlation between TTR and mortality rates was assessed. Out of the 203 patients, 116 (57%) achieved therapeutic range at least once, with a mean TTR of 43.1% (± 22.4) and a median of 39%. Nevertheless, the overall mean TTR for all patients was 24.6% (± 27.3), with a median of 18.8%. During the study period 25 (12.3%) patients have died, of them 9 (4.4%) within 30 days and 16 (7.9%) within one year. Higher TTR was associated with reduced 30-day (p = 0.051) and one-year (p = 0.045) mortality rates. Receiver Operating Characteristic (ROC) analysis identified a TTR threshold of 21.5% for predicting one-year mortality, demonstrating a high negative predictive value (NPV) of 96.8% but a low positive predictive value (PPV) of 12%. Patients with acute PE who achieved higher TTR exhibited better outcomes at 30 days and one year. However, most patients did not reach adequate TTR levels, leaving its role as an independent prognostic indicator uncertain. Larger studies are necessary to optimize therapeutic strategies and improve outcomes in intermediate-risk PE patients.