Real-world Evidence of High-risk Mortality Factors in Venous Thromboembolism: a Retrospective Cohort Study

Study population and characteristics This retrospective cohort study initially screened 105,168 consecutive hospitalized patients at Shihezi People's Hospital from February 2022 to June 2025. Acute symptomatic venous thromboembolism (VTE) was defined as newly diagnosed deep vein thrombosis (DVT) or pulmonary embolism (PE) by imaging confirmation. Diagnosis was confirmed by at least one of the following objective methods: compression ultrasonography showing non-compressible venous segments for DVT, or computed tomography pulmonary angiography (CTPA) showing intraluminal filling defects for PE. All diagnoses were extracted from the hospital's VTE Dynamic Management Data System.Symptom status was assessed at the time of imaging. The research protocol was approved by the ethics committees. The requirement for written informed consent was waived, as the study used clinical information obtained during routine clinical practice. This study was approved by the Ethics Committee of Shihezi People's Hospital (SHZ-2403).

Inclusion criteria: (1) age ≥ 18 years; (2)acute VTE as defined above; (3) complete electronic medical records available.

Exclusion criteria: (1) missing key variables (e.g., discharge status, follow-up data, or ≥20% of prespecified risk factors); (2) chronic VTE (symptom duration > 31 days); (3)VTE diagnosed at another hospital without confirmatory imaging available.

Study Design and Grouping Definition The hospitals databases were searched for clinical diagnoses and imaging examinations using the VTE Dynamic Management Data System (VTE Intelligent Diagnosis and Treatment Support System, developed by DrBreath Medical Company, Beijing). Accordingly, all patients diagnosed with VTE were classified into two mutually exclusive groups based on their vital status at the end of follow-up: the Survival Group (patients alive at last contact) and the Death Group (patients who died from any cause during hospitalization or follow-up). This outcome-driven dichotomy was established to compare baseline characteristics, comorbidity profiles, and the distribution of high-risk factors between survivors and non-survivors, thereby enabling the identification of mortality-associated determinants. No additional matching or stratification was applied at this stage.

Endpoints and Clinical Follow-up The primary endpoints. The primary endpoint of this study was the occurrence of all-cause death during the follow-up period. Based on this endpoint, patients were dichotomized into the Survival Group and the Death Group to enable comparative analyses of baseline characteristics, comorbidity profiles, and risk factor distributions. All-cause mortality in VTE patients assessed throughout the entire follow-up period from the date of VTE diagnosis (baseline) until the end of the study period (June 1, 2025).

Secondary endpoints included the following outcomes assessed at prespecified time points: 1) In-hospital mortality: defined as death occurring during the index hospitalization, with the time at risk beginning at the date of hospital admission and ending at the date of hospital discharge or in-hospital death. 2) 30-day mortality: defined as death from any cause occurring within 30 days following the date of VTE diagnosis. 3) 90-day mortality: defined as death from any cause occurring within 90 days following the date of VTE diagnosis. 4) Recurrent VTE: defined as new onset of objectively confirmed deep vein thrombosis or pulmonary embolism following complete symptomatic resolution of the index event. Recurrent VTE was assessed at 30 days, 90 days, and at the end of follow-up. 6) Length of hospital stay: calculated as the total number of days from admission date to discharge date or in-hospital death. All secondary outcomes were independently adjudicated by the clinical event committee. Follow-up time was calculated from the date of VTE diagnosis to the date of death, last contact, or study end (June 1, 2025), with censoring applied for patients lost to follow-up during study. Collection of follow-up information was mainly conducted through review of hospital charts, and additional follow-up information was collected through contact with patients, relatives, and/or referring physicians by phone and/or mail with questions regarding vital status, recurrent VTE, bleeding, invasive procedure, acute myocardial infarction, stroke and status of anticoagulation therapy.

Data Sources and Screening Process for High-Risk Factors All data were sourced from the hospital's electronic medical record system by the VTE Intelligent Decision Support System. For each patient with VTE, general medical history and comorbidities were extracted. Data were automatically checked for missing or contradictory input and values out of the expected range. Additional monitoring for the quality of data was performed at the general office of the registry. Screening Process for High-Risk Factors: Key high-risk factors were initially identified based on the latest