862 



HANDBOOK OF PHYSIOLOGY ^- CIRCULATION II 



BEFORE RESECTION 



.186 



# 



mean flow 660 ^„^ 

 475 320 



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(mmHg) 



AFTER RESECTION 



,140 



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80 





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fig. 33. Congenital coarctation. Tracings from above downward both before and after resection 

 are : descending thoracic aorta pressure, blood How through the coarctation area, low-frequency 

 phonocardiogram, and high-frequency phonocardiogram. Blood flow records both before and after 

 resection were made at the same sensitivity setting of the electromagnetic flowmeter. Zero reference 

 after resection was not obtainable because of danger of rupture of the suture line. On the basis that 

 zero was somewhat lower than the lowest flow point, the mean flow was estimated to be greater than 

 1800 ml/min after resection, while the mean flow before resection was 475 ml/min. Some constric- 

 tion remained after resection and suture. 



fig. 34. Tricuspid regurgitation after the differential pressure 

 method of Miiller & Shillingford (29). Blood flow is recorded 

 between the superior vena cava and the right atrium in a 

 normal subject in record A, and in a patient with tricuspid 

 incompetence and high venous pressure in record B. 



by the contour of the aortic pressure pulse alone, 

 because normally it greatly exceeds the pulmonary 

 artery pressure at all times throughout the cardiac 

 cycle. Because of this situation, the murmur is con- 

 tinuous throughout the cardiac cycle. 



Figure 32 illustrates a flow pulse through a ductus 

 of an unusual type. In this situation, chronic pulmo- 

 nary hypertension had developed until the pulmo- 



nary pressure exceeded that in the aorta during 

 systole, and was less than that in the aorta during 

 diastole. (The larger pulse pressure in the pulmonary 

 tree than in the systemic arteries probably resulted 

 from the smaller compliance of the pulmonary tree.) 

 As a result, ductus flow was from pulmonary artery 

 to aorta during systole, and from aorta to pulmonary 

 artery during diastole. 



Coarctation of the aorta also produces a viscous 

 type flow through the stenotic region (43, 49). Most 

 patients with coarctation have a severe degree of the 

 type illustrated in figure 33. The differential pressure 

 and murmur envelope both follow the contour rule 

 with reference to the flow pulse. Flow pulses in the 

 aortic branches are considerably altered (43). 



Tricuspid Valve 



Blood flow between the superior vena cava and the 

 right atrium was measured by a pitometer by 

 Miiller & Shillingford (29). This record probably 

 represents a close approximation of the flow pulse at 

 the tricuspid valve except for the period of atrial 

 contraction which is inverted to show forward flow 

 (fig. 34)- 



