1. A system for determining cardiovascular information for a patient, the system comprising: at least one computer system configured to: receive patient-specific data regarding a geometry of the patient's heart; create a three-dimensional model representing at least a portion of the patient's heart based on the patient specific data; create a physics-based model relating to a blood flow characteristic of the patient's heart; and determine a fractional flow reserve within the patient's heart based on the three-dimensional model and the physics-based model.