EVANS BLUE DYE 



WH iJ-J- 



PHYSIOLOGIC CONSEQUENCES OF CONGENITAL HEART DISEASE 433 



METHYLENE BLUE DYE 



T-1824 

 0.16 mg /kg 



Oximeter Left Ear 



Cuvette Oximeter Radial Artery 



FIG. 6. Aiterial dilution curves recorded by cuvette and ear oximeters following injection of in- 

 dicator into superior vena cava of a girl, age 5, with ventricular septal defect, right-to-left shunt, and 

 pulmonary hypertension. Method for determining magnitude of right-to-left shunt has been applied 

 to cuvette-oximcter curve. Triangles are constructed by drawing vertical lines to peaks of humps, 

 build-up time of secondary hump being taken as 44 per cent of maximal concentration time (time 

 from injection to secondary peak). Area of first or shunt triangle {slanted lines) is divided by sum of 

 areas of two triangles shown. In this instance, proportion was 25%. [From Fox & Wood (iia).] 



tude of the right-to-left shunt from the dye curve, 

 giving values that correlate well with those calculated 

 from the values for oxygen saturation of venous and 

 arterial blood, has been devised by Swan and asso- 

 ciates (243) (fig. 6). 



NORMAL VENOUS INDICATOR-DILUTION CURVE. The 



recently developed dye, indocyanine green, makes 

 possible accurate recording of dilution curves in the 

 venous circulation either upstream or downstream 

 from the injection site, independent of the variations 

 in the oxygen saturation of the blood (io8, 1 1 1). 



Venous dilution curves recorded upstream from 

 the injection site in a patient and a dog without 

 intracardiac shunts are shown in figure 7. After 

 injection of dye into the pulmonary artery the dye- 

 blood mixture was sampled from the right ventricle, 

 coronary sinus, and venae cavae on the venous side, 

 and also from the radial artery. In the right ventricu- 

 lar curve one notes, in addition to the small deflection 

 and generalized damping of the curve, the delayed 

 appearance of the dye at this sampling site as com- 

 pared to its appearance in the radial artery. The 

 dilution curve recorded from the coronary sinus, 

 owing to the rapidity of flow and relatively small 

 capacity of this bed, is similar to an arterial dilution 

 curve. Also it is seen that the right ventricular "mixed 

 venous curve" resembles a composite of the superior 

 and inferior caval curves and that, as a result of the 

 relatively much smaller blood flow from this site, the 

 effect of the coronary-sinus curve on the "'mixed 

 venous curve" is not apparent. The dynamic response 

 of the sampling and recording systems used for the 

 transcription of these venous dilution curves was too 

 slow to follow the rapid variations in indicator con- 



centration that occur with the heartbeat. The effects 

 of variations in the dynamic response of the recording 

 system on the contour of dilution curves recorded 

 from the pulmonary artery of a normal dog are 

 illustrated in figure 8. The current practically useful 

 techniques for detection and quantitation of left-to- 

 right shunts or valvular regurgitation by methods 

 involving sampling from the central circulation 

 require only that the areas encompassed by these 

 curves be measured accurately (223). Measurement 

 of these areas does not necessitate accurate reproduc- 

 tion of rapid variations in concentration occurring 

 with each heartbeat; therefore instruments with a 

 relatively slow dynamic response can be used success- 

 fully in these methods. 



The second channel into the heart required for 

 simultaneous injection of indicator and recording of 

 resultant dilution curves from multiple selected sites 

 on the right side of the heart can be provided in one 

 of three ways via the peripheral veins: /) a right 

 heart catheter with double lumen, 2) two right heart 

 catheters, or 3) a right heart catheter containing a 

 second very small catheter for injection of the indica- 

 tor. Because of greater flexibility, the latter two 

 methods are preferred (274). 



LOCALIZ.\TION AND CiUANTITATION OF LEFT-TO-RIGHT 



SHUNTS. Venous sampling techniques are especially 

 useful in the detection and quantitation of left-to-right 

 shunts (no, 206). They are more sensitive for this 

 than studies of blood oxygen content or even of blood 

 oxygen saturation by cuvette oximetry, since oxygen 

 is normally present in venous blood but the presence 

 of any early-appearing dye on the right side of the 

 heart is abnormal. The indocyanine green dye 



