Coronary Circulation and the Tail of First-Pass Indicator Dilution Curves
In a series of canine heart-lung preparations, single-pass indicator dilution curves were obtained with and without cannulation of the coronary sinus. Further evidence was obtained that the tails of the curves are significantly elevated above the tails predicted from the simple one-dimensional random-walk relation.
To provide estimates of the contributions which dye circulating through the coronaries might make to the tails, curves were obtained in the same preparation with and without cannulation, and at high and low mean arterial pressure. A method was developed for cannulation which permitted sampling through an exterior low-resistance cannula system which was secured in the coronary sinus without producing serious obstruction of the coronary sinus tributaries or interference with the conduction system.
Although the classical exponential down-slope gave better agreement than the random-walk relation, the experimental curves were frequently elevated and prolonged when compared to the exponential curve. The difference in area amounted to approximately 4.5%. In experiments at high mean arterial pressure without bypass of coronary dye the tail was significantly higher on the average by 3% compared to the tail in the same preparation with bypass at low pressure. Estimating that 60 to 70% of coronary dye would be successfully bypassed, the total coronary contribution to the tail of 4 to 5% of dye on the average is not sufficient to account for the excess of experimental tails over random-walk curves.
- Received September 9, 1963.
- © 1964 American Heart Association, Inc.