Studies on mitral valve function; effect of acute hypervolemia, premature beats and other arrhythmias.

A direct method for studying valvular competence is described based on changes in impedance in the blood induced by injections of concentrated saline. It does not require withdrawal of blood samples and may be repeated at frequent intervals in the same animal. It detected mitral insufficiency in the absence of significant changes in atrial pressure tracings. Mitral insufficiency was observed frequently in association with ventricular arrhythmias, occasionally with atrial arrhythmias and in half of the dogs made acutely hypervolemic.