['Ultrasonographic evaluation of systemic arterial function is widely available, and a close relation of endothelial function in the coronary and brachial arteries has been documented. It is unknown, however, whether a similar correlation exists for their 2 microcirculatory territories and thus whether assessment of the systemic microcirculation can be used similarly as a surrogate marker of myocardial perfusion.', 'Twenty-three patients with documented coronary artery disease (CAD; 66+/-9 years old, 18 men), 16 patients with syndrome X (SX; 56+/-5 years old, 13 women), and 45 healthy control subjects (C; 34+/-9 years old, 22 men) were studied. Myocardial perfusion was measured at rest and after dipyridamole (0.56 mg. kg(-1). min(-1) over 4 minutes) by PET, and brachial artery blood flow was measured at rest and after transient forearm ischemia by standard Doppler ultrasound techniques. Dipyridamole increased myocardial perfusion in all groups (mL. g(-1). min(-1): CAD, 0.89+/-0.27 versus 1.62+/-0.67, P:<0.001; SX, 0.82+/-0.16 versus 1.67+/-0.49, P:<0.001; and C, 0.82+/-0.15 versus 2.32+/-0.64, P:<0.001). Postocclusion forearm flow increased similarly in all groups (CAD, 52+/-18 versus 174+/-77 mL/min, P:<0.001; SX, 49+/-29 versus 202+/-82 mL/min, P:<0.001; and C, 61+/-34 versus 229+/-108 mL/min, P:<0.001). No significant correlations were found between peripheral and myocardial microcirculatory beds for either resting flow, hyperemic flow, or flow reserve in any of the groups (r(2)<0.1, P:=NS).'] Does peripheral flow response to transient arterial forearm occlusion reflect myocardial perfusion reserve?