This 6-week, Phase 2, randomized, double-blind, crossover, investigator-initiated, single-center study will determine the feasibility of detecting the effect of darusentan 100 mg once daily on the extent of myocardial perfusion heterogeneity in subjects with documented CAD, as measured by cardiac PET imaging. Prior to the initiation of any study procedures, an Informed Consent Form and HIPAA Authorization will be reviewed and signed by each subject. Screening assessments and evaluations may be conducted over a period of not more than 4 weeks.