PULSATILE BLOOD FLOW 



86 1 



Ductus Open 



Ductus Occluded 



Flow f 



"J? 



Back + 



AGE 3 YR 

 28 FEB 1958 



fig. 30. Flow in the descending 

 thoracic aorta distal to a ductus arterio- 

 sus while patent and after the ductus 

 was occluded. Simultaneous recording 

 of the descending aorta pressure was 

 made by means of a needle inserted 

 near the square-wa%'e electromagnetic 

 probe. 



thoracic flow following closure of this ductus may be 

 taken as the shape of the normal flow in the human 

 descending thoracic aorta. Variations in contour 

 show basic similarities to those of the dog's descending 

 thoracic aorta of section III. It is of interest to note 

 that the mean forward flow in the descending thoracic 

 aorta distal to a patent ductus arteriosus is not 

 affected by closure of the ductus. This finding indi- 

 cates what is confirmed by flow in the descending 

 thoracic aorta proximal to the patent ductus, namely, 

 that the left ventricle compensates for a ductus 

 arteriosus by increasing its output just a sufficient 

 amount to make up for the flow passing through this 



-JWtESSUaE 

 180-1 A«t<» 



fig. 31. Blood flow through a patent ductus arteriosus. Con- 

 tour of the flow pulse follows closely that of the contour of the 

 aortic pressure thereby indicating strong predominance of 

 resistant blood flow in this situation. The murmur was con- 

 tinuous and had an envelope the contour of which followed the 

 contour rule. Pulmonary pressures were normal. 



fig. 32. Blood flow through a patent ductus arteriosus in a 

 patient with pulmonary hypertension. There was a net flow of 

 blood into the aorta. Flow from pulmonary artery into the 

 aorta took place during systole, and from aorta into the pulmo- 

 nary artery during diastole. The greater pulse pressure in the 

 pulmonary artery as compared to that in the aorta undoubtedly 

 resulted from the lower compliance of the pulmonary tree as 

 compared to that of the systemic arterial tree. The three records: 

 aortic pressure, pulmonary artery pressure, and patent ductus 

 flow, were taken at different times in rapid succession. 



shunt to the pulmonary artery. The flow through the 

 ductus is predominantly viscous in type, as its contour 

 follows closely that of the contour of the differential 

 pressure between the aorta and pulmonary artery 

 (fig. 31). The envelope of the murmur follows the 

 contour rule of the differential pressure and flow 

 pulse in a viscous flow situation. The murmur 

 envelope and flow contour are closely represented 



