1. A method for guiding delivery of a therapeutic agent, whose efficacy is sensitive to shear stress, to a heart of a patient, the method comprising the steps of: receiving user input specifying a dosage of the therapeutic agent; identifying a catheter for delivering the specified dosage of the therapeutic agent; providing a flow model for the identified catheter by retrieving data from computer-readable memory; assessing sensitivity of the therapeutic agent to shear stress by retrieving data from computer-readable memory; out of a range of candidate values, selecting a preferred value of a parameter for delivering the therapeutic agent in response to: computing shear stress for a plurality of the candidate values in response to running the flow model on a computer; and comparing the computed shear stress to the assessed sensitivity; and outputting a message for user receipt based on the preferred value.