Cardiovascular surgery entails high costs and risks, yet pre-operative planning largely depends on clinical experience, with limited ability to predict patient-specific hemodynamics. In-silico modeling offers a framework to virtually evaluate and optimize surgical strategies. By addressing methodological challenges in pre- and post-operative comparisons, this work advances the development of reliable cardio- vascular digital twins, potentially reducing the need for costly and ethically complex in-vivo studies. This study focuses on the David procedure, in which an aneurysmal ascending aorta is replaced by a prosthetic graft while preserving the native aortic valve. The objective is to quantify the impact of the intervention on left-heart hemodynamics through patient-specific numerical simulations. A central methodological challenge is the consistent comparison of pre- and post-operative hemodynamics when multiple factors, i.e. geometry and structural mechanics properties, are simultaneously altered by surgery. In this work, all surgery-induced changes are explicitly modeled and their effects are quantitatively assessed. We propose a systematic workflow that enables controlled pre-/post-operative analyses by progressively incorporating CT-derived geometric remodeling and modifications in structural properties behavior. This approach allows the relative contribution of each factor to the observed hemodynamic alterations to be isolated, leading to a robust interpretation of the impact of the David procedure and associated graft parameters. Direct Numerical Simulations are performed using an in-house solver for fully coupled fluid – structure – electrophysiology interactions based on an immersed boundary framework, extended to capture the distinct mechanical behavior of the native aortic aneurysm and the prosthetic graft. A parametric study is carried out by varying graft length, radius, and material properties to evaluate their influence on flow and pressure patterns. The results reveal significant alterations in left-heart and aortic hemodynamics following the David procedure, with a marked sensitivity to graft design parameters. These findings demonstrate that graft selection has a measurable impact on post-operative hemodynamics. Ongoing work aims to extend the framework to a patient cohort, enabling statistical analysis and providing predictive insights to support surgical decision-making.