Directional vs bidirectional Doppler velocimeter.
D001281:Atrial Fibrillation / Q000503:physiopathology; D001783:Blood Flow Velocity; D006325:Heart Atria; D006327:Heart Block / Q000503:physiopathology; D006801:Humans; D007601:Jugular Veins; D008722:Methods; D013350:Subclavian Vein