THE LEFT ATRIAL X DESCENT

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Abstract
Left atrial pressure tracings from cases of mitral valvular disease with changing P-R intervals show that "x" descents vary in time with atrial activity and do not maintain a constant relationship to "c" waves or to electrocardiographic R waves. In a patient with prolonged P-R interval no trough of pressure occurred between "c" and "v" peaks. These observations support the belief that atrial relaxation may be chiefly or solely responsible for the "x" descent. The magnitude of "x" descent is unlikely to be a valuable guide to the presence of mitral regurgitation because it is dependent upon many variable factors.