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 an anatomical structure of the patient, the anatomical structure including at least a portion of a plurality of coronary arteries emanating from an aorta; create a three-dimensional model representing a first portion of the anatomical structure based on the patient-specific data, the first portion of the anatomical structure including at least the portion of the plurality of coronary arteries, the three-dimensional model representing at least one fluid flow inlet and at least one fluid flow outlet; create at least one boundary condition model representing fluid flow through at least one of the at least one inlet or the at least one outlet, based at least in part on a mass or a volume of myocardial tissue; and determine a fractional flow reserve within the first portion of the anatomical structure based on the three-dimensional model and the at least one boundary condition model.