1. A system for determining patient-specific time-varying cardiovascular information, the system comprising: at least one computer system configured to: receive time-varying patient-specific data regarding a geometry of at least a portion of an anatomical structure of the patient at different times; create a three-dimensional model representing at least the portion of the anatomical structure of the patient based on the time-varying patient-specific data, the three-dimensional model including time-varying information regarding at least one of blood vessel position, deformation, orientation, or size; and determine information regarding a change in a blood flow characteristic over time within the anatomical structure of the patient based on the three-dimensional model and a physics-based model relating to the anatomical structure of the patient.