PHYSIOLOGIC CONSEQUENCES OF CONGENITAL HE.ART DISEASE 



461 



Expressed as % of systemic blood flow. f Expressed as % of pulmonary blood flow. 



syndrome" to include all patients with a communica- 

 tion between the right and left sides of the heart 

 associated with severe pulmonary hypertension and a 

 predominant right-to-left shunt. It seems more 

 pertinent to include all cases of a certain defect, such 

 as ventricular septal defect, under the same name, 

 and to realize that the cyanotic group represents 

 merely a further progression of the pulmonary ob- 

 structive changes that may occur. 



Atrial Septal Defects 



Defects of the atrial septum result in an abnormal 

 communication between the two low-pressure input 

 chambers of the heart. The predominant flow through 

 such defects is usually in the left-to-right direction 

 and it is frequently large. In spite of greatly increa,sed 

 blood flow, pressures in the right side of the heart 

 usually remain normal although they may increase 

 in adulthood. The blood flow from the left ventricle 

 is usually within normal limits. Thus the left-sided 

 (systemic) circulation is a normal-pressure normal- 

 volume system and that in the right side is a normal- 

 pressure high-flow system. 



HEMODYNAMIC FINDINGS. The average and range of 

 various hemodynamic values in 57 patients with 

 atrial septal defects are shown in table 6 (258). The 

 ages ranged from 3 to 58 years; more than one-half 

 of the patients were between 2 i and 40 years of age. 

 The average pulmonary-artery pressure in this series 

 was slightly elevated. Forty of the 57 patients had 

 pulmonary-artery pressures that were normal or 

 minimally elevated, 5 had a systolic pressure between 

 41 and 60 mm of mercury and 12 had severe pul- 

 monary hypertension with systolic pressures greater 

 than 60 mm. All 12 patients with severe pulmonary 

 hypertension were adults; of iB patients less than 21 

 years of age only one, a 412-year-old child, had 

 moderate elevation of the pulmonary-artery pressure. 

 There was no correlation between the magnitude 

 of pulmonary blood flow and pulmonary-artery 



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2 

 O 



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20 40 60 80 100 



PULMONARY ARTERY MEAN PRESSURE (mm Hg ) 



FIG. 32. Relation of pulmonary blood flow to pulmonary- 

 artery mean pressure in 54 patients with interatrial com- 

 munications. Note apparent division of data so that flow values 

 are almost independent of pressure in those patients with a 

 mean pulmonary-artery pressure of less than 30 mm of mercury. 

 In patients with a mean pulmonary-artery pressure in excess 

 of 40 mm of mercury there was an inverse relation between 

 pressure and flow. 



pressure in those patients without pulmonary hyper- 

 tension, the pulmonary-artery pressure remaining 

 normal or only minimally elevated despite a large 

 pulmonary blood flow in these patients (fig. 32). 

 However, in the group with severe pulmonary hyper- 

 tension there was an inverse relation between pul- 

 monary blood flow and mean pulmonary-artery 

 pressure. 



In this group of 57 cases the average pulmonary 

 blood flow of 8.7 liters per min per m- was more than 

 twice the normal flow. The systemic blood flow at 

 rest was within the range of normal in 69 per cent 

 of the patients in whom it was measured. Only five 

 of the group had more than a minimal decrease in 

 systemic flow, and all of these had pulmonary hyper- 

 tension. No correlation was found between the 



