432 HANDBOOK OF PHYSIOLOGY ^ CIRCULATION I 



Systole 



Diastole 



Diastole 



Systole 



Systole 



FIG. 4. Diagrammatic illustration of effect of valvular regurgi- 

 tation on passage of indicator through cardiac chambers. In 

 center of figure are illustrated normal {broken line) and abnormal 

 (solid line) dilution curves associated with severe vahular regur- 

 gitation. Indicator is injected at inflow to cardiac chamber 

 {panel a). When it flows into atrium during next \'entricular 

 systole [panel b) it is diluted by the volume of blood regurgitated 

 into ventricle during succeeding diastole (panel c), and during 

 subsequent systole (panel d) a portion of dye-blood mixture is 

 regurgitated back into atrium and a portion is ejected forward 

 into aorta; this process is repeated during successive cardiac 

 cycles (panels e and /) so that time required for dye to be cleared 

 from cardiac chambers is markedly prolonged. 



curve is obtained at the sampling site in the systemic 

 artery. 



The middle panel illustrates the situation with a 

 left-to-right shunt such as would occur in atrial or 

 ventricular septal defect or in aortic-pulmonary 

 communication. Pulmonary blood flow is increased 

 owing to recirculation of the blood through the lungs 

 via the defect. The resulting dilution curve is de- 

 creased in amplitude owing to the increased volume 

 of blood in which the dye is diluted as a result of the 

 high pulmonary flow. The curve also shows dispro- 

 portionate prolongation of the disappearance slope 

 due to recirculation of the dye-blood mixture through 

 the lungs. A similar pattern may be recorded in 

 patients who have significant regurgitation at one or 

 more of the valves in the circulatory system between 

 the injection and sampling sites. In such patients the 

 dilution curve is distorted partly by the changes in 

 flow and volume of the circulation accompanying the 

 frequently associated congestive heart failure and 

 partly by slow clearance of dye from the heart due to 

 backward as well as forward flow of dye-blood 

 mixture across the incompetent valve (fig. 4). A 

 simple, useful method for estimating the magnitude 

 of left-to-right shunts on the basis of the degree of 



Iniecfion ■nio 



Pulmonary ortery 



Right ventricle 



10 sec 



FIG. 5. Method of localizing right-to-left shunt by indicator- 

 dilution curves in case of pulmonary stenosis and right-to-left 

 shunt through ventricular septal defect. Below: arterial dilu- 

 tion ciir\es after injection (arrows) into pulmonary artery and 

 right ventricle. When dye is injected downstream to shunt, 

 as into pulmonary artery (left), an essentially normal dye curve 

 results; when dye is injected upstream to shunt, part escapes to 

 left side of heart \ia sentricular septal defect and appears 

 prematurely in systemic artery to produce early abnormal 

 deflection of curve. Dye traversing normal pathways appears 

 later, and characteristic double-humped curve results. Differ- 

 ence in these two curves localizes shunt to right ventricle. 



distortion of the disappearance slope has been de- 

 scribed by Carter and associates (52). 



The lower panel in figure 3 illustrates the situation 

 with a right-to-left shunt. When the dye-blood 

 mixture reaches the defect, a portion is shunted right 

 to left and enters the systemic circulation directly. 

 These dye-blood particles therefore arrive at the 

 sampling site before those that traverse the longer 

 normal circulatory pathway through the lungs. An 

 abnormal initial deflection is produced and the 

 characteristic double-humped contour associated 

 with a right-to-left shunt results. 



This characteristic distortion caused by a right-to- 

 leit shunt may be used to localize the site of shunts by 

 injecting dye into a site in the right heart that is 

 downstream to the chamber from which the shunt is 

 occurring. An essentially normal dilution cur\e is 

 recorded at an arterial sampling .site (fig. 5). If the 

 catheter is then withdrawn to the chamber from which 

 the shunt is occurring and the injection repeated, an 

 abnormal initial deflection appears on the dilution 

 curve characteristic of a right-to-left shunt, thus 

 localizing the defect to this chamber. 



A simple, useful method for calculating the magni- 



