The goal of this observational study is to evaluate the predictive efficacy of the Modified Caprini Risk Assessment Score and D-Dimer in identifying and managing lower extremity venous thrombosis (LEVT) among cardiothoracic surgery patients in Baghdad. The main questions it aims to answer are: Does combining the Modified Caprini Score with D-Dimer improve the accuracy of predicting lower extremity venous thrombosis (LEVT) compared to using each tool independently? Can these tools effectively guide clinical decisions for lower extremity venous thrombosis (LEVT) prevention and management in this patient population? Participants will: Undergo risk assessment for lower extremity venous thrombosis (LEVT) using the Modified Caprini Score and have their D-Dimer levels measured during their hospital stay. Be monitored for clinical outcomes, including confirmed lower extremity venous thrombosis (LEVT) incidence, need for anticoagulation therapy, and complications such as pulmonary embolism or recurrent thrombosis.