Effect of Heart Rate on Aortic Insufficiency as Measured by a Dye-Dilution Technique

¹ From the Departments of Physiology, University of Utah and Latter-day Saints Hospital, Salt Lake City, Utah

Measurements of the distance a labeled particle of blood travels back up the descending aorta during a single diastole have been carried out at two different heart rates in each of three patients with aortic insufficiency. From these measurements, the ratios of back flow per unit time at the slow heart rate to backflow at the faster heart rate were found to be 1.61, 1.71, and 1.75. From an analysis of the hemodynamic factors involved, it seems likely that backflow is overestimated at the slow heart rates by this technique due to the development of laminar flow late in diastole.