Effects of Quantitatively Controlled Left Ventricular-Atrial Regurgitation on Indicator - Dilution Curves in the Dog

Dye-dilution curves were recorded from the aortic arch of dogs with left ventricular-atrial regurgitation produced surgically by a shunt from the apex of the left ventricle to the left atrial appendage. Rate of regurgitation was monitored by an electroturbinometer and was varied from 0.9 to 3.3 liters per minute. In each dog, reciprocal of the downslope and variance of curves obtained after injection of dye into the left atrium varied directly with rate of backflow and inversely with net cardiac output. These effects of regurgitation were not due to change in transit volume. Estimates of regurgitation based on change in reciprocal of slope correlated closely with flowmeter values and were more accurate than estimates based on change in variance. Back flow was underestimated by curves recorded after injection of dye into the pulmonary artery.