Brachial ArteryVasodilationEndothelium, VascularArteriesForearmRegional Blood FlowNitroglycerinHyperemiaCarotid ArteriesRadial ArteryPulmonary ArteryFemoral ArteryVasodilator AgentsBlood Flow VelocityCerebral ArteriesRenal ArteryMesenteric ArteriesCarotid Artery, CommonBasilar ArteryAxillary ArteryUlnar ArteryBlood PressureUltrasonography, DopplerSubclavian ArteryVertebral ArteryIliac ArteryUltrasonography, Doppler, PulsedCoronary Artery Bypass