Circulation
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To examine whether an extremely enlarged left atrium (giant left atrium) obstructs the venous return from the inferior vena cava (IVC), the velocity of IVC flow was measured at its junction with the right atrium (IVC orifice) in patients with mitral stenosis by use of color and pulsed-wave Doppler echocardiography from a right parasternal longitudinal plane. ⋯ A giant left atrium in patients with mitral stenosis obstructs venous return at the IVC orifice by marked displacement of the atrial septum toward the right atrium.
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When used to reverse the anticoagulant effect of heparin, protamine sulfate often causes vasodilation that can lead to systemic hypotension. Protamine is rich in the basic amino acid arginine, which is the precursor of endothelial cell synthesis of nitric oxide, and nitric oxide is the active component of endothelium-derived relaxing factor (EDRF). ⋯ This study demonstrates that protamine stimulates the release of EDRF from arterial endothelium, and that endothelium-dependent vasodilation may be an important cause of systemic hypotension during protamine infusion.