Comparison of Dilution Technics Using Aortic Injection with Upstream Sampling for Assessment of Aortic Regurgitation.

• Warner and Toronto have described a method for detecting and quantitating aortic regurgitation. This method involves simultaneous recording of indicator dilution curves from the left radial and femoral arteries following injections, at specific phases of the cardiac cycle, into the descending aorta at and downstream from the origin of the left subclavian artery. From these measurements they determined the distance down the aorta from the origin of the subclavian artery beyond which no dye would return to this artery during the diastolic phase of the cardiac cycle. This distance multiplied by an estimated average cross-sectional area of this segment of the aorta yields the volume of backflow per stroke in this portion of the arterial bed if nonlaminar flow is assumed. This type of study was applied to experimental animals and to patients with and without aortic regurgitation.