Panel A: Examle of a cross section of a right coronary artery (RCA, red circle) and right internal mammary artery (IMA, yellow circle) in same axial imaging plane. Panel B. Bar graph representing the % change from baseline in vasoreactive parameters: area, velocity and blood flow with isometric handgrip exercise (IHE) in the IMA and RCA of health controls (N=27, blue) and patients with coronary artery disease (CAD, N=21, red). Panel C. L-NMMA (monomethy-L-arginine, NOS inhibitor) study in 9 healthy adults: Summary results for % change from baseline in IMA area, velocity and blood flow changes with IHE for control (blue bars, before L-NMMA) and during L-NMMA infusion (yellow bars), showing that L-NMMA blocks the normal increase in all three vasoreacive measures with stress. Error bars indicate standard error of the mean. ◊p<0.001 vs control; ◊◊p<0/0001 vs control; *p<0.01 vs baseline; **p<0.0001 vs baseline. CSA: cross-sectional area; FV: flow velocity; BF: blood flow.