Direct Determinations of Aortic Blood Flow in Patients with Aortic Regurgitation

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Abstract
Instantaneous ascending aortic blood flow and left ventricular and central aortic pressure were determined at the time of operation in nine patients with severe aortic regurgitation. In six, the heart rate was controlled and increased by electrical stimulation between 50 and 170 beats/min. The relative duration of diastole decreased, and that of systole increased at faster heart rates. The mean systolic ejection rate fell, and regurgitant flow rates remained relatively constant. Thus, the per cent regurgitation was not reduced at faster rates. Following isoproterenol administration, the faster heart rate lengthened the relative duration of systole, abbreviated that of diastole, and increased the systolic ejection rate. Net result was an increased total forward flow and a reduced per cent regurgitation, but when the heart rate was held constant, the total forward stroke volume was ejected more rapidly, but the total forward and regurgitant flows per beat and per minute, and consequently the per cent regurgitation did not change. Assessments of left venticular function also were made in two patients.