PHYSIOLOGIC CONSEQUENCES OF CONGENITAL HEART DISEASE 



453 



shunts predominantly in the right-to-left direction 

 are found. 



In considering the size of the defect, it is obvious 

 that when the opening reaches a certain size there 

 will be an equalization of pressures in the two circula- 

 tions and, in the case of ventricular septal defect, the 

 ventricles will function as a single pumping chamber 

 with two outlets. 



Although the pulmonary vascular resistance is high 

 in the prenatal period, this resistance normally 

 declines rapidly after birth. With this fall in resistance 

 some infants with ventricular septal defects die in the 

 first few months of life from heart failure with ex- 

 cessive blood flow through the lungs, whereas other 

 infants with defects of similar size respond with a 

 return to a high pulmonary vascular resistance, 

 survive and lead an active life for many years (34). 



Another factor that has been considered important 

 in the hemodynamics of ventricular septal defect, 

 overriding of the aorta (the anatomic position of the 

 defect in relation to the aorta), does not appear to 

 play a significant role in determining the direction and 

 magnitude of shunts across the defect. 



In the past, varying degrees of severity of ventricu- 

 lar septal defects have been considered to be different 

 entities, and various names to describe these entities 

 have been in general use. For example, a very small 

 ventricular septal defect with normal pressure in the 

 right side of the heart has been called ''maladie de 

 Roger," and anomalies characterized by large 

 ventricular septal defect, overriding of the aorta, and 

 cyanosis have been termed "Eisenmenger complex." 



(91). 



It is generally recognized now, with increased 

 knowledge of all gradations of ventricular septal 

 defects and associated hemodynamic alterations, that 

 all should be regarded as ventricular septal defects of 

 varying severity and that terms designating them as 

 separated entities ha\e for the most part outlix'ed their 

 usefulness. 



AVERAGE AND R.-^NGE OF HEMODYNAMIC DATA IN 



VENTRICULAR SEPTAL DEFECT. The average and range 

 of pressures and flows in 38 patients with ventricular 

 septal defect are given in table 5 (80). There was a 

 wide range in the age of the patients, extending from 

 7 months to 44 years, 24 of whom were less than 20 

 years of age. Pressures in the pulmonary artery varied 

 from normal values to values similar to tho.se found in 

 the systemic arterial system. In 12 patients, pressures 

 in the pulmonary artery were within the range of 

 normal, in 10 they were moderately elevated, and in 



TABLE 5. Average and Range of Hemodynamic Data in 

 j8 Patients With I 'entricular Septal Defect 



* Obtained in 16 patients. 



16 the pulmonary systolic pressures were equivalent 

 to those found in the systemic arterial system. 



In this series the average pulmonary blood flow of 

 8.0 liter per min per m- was more than twice the 

 normal value for pulmonary flow. 



Values from two to four times normal were obtained 

 in patients with normal pulmonary-artery pressures 

 and averaged 5.6 (3.5-9. i) liter per min per m-. The 

 highest values occurred in patients with moderately 

 elevated pulmonary-artery pressures. These flows were 

 from 3 to 8 times normal and averaged 11.5 (7.7- 

 17.1) liters per min per m-. In those with equivalent 

 pressure relationships between the right and left sides 

 of the circulation, contrasting pictures were seen. In 

 seven of these patients, less than 12 years of age, there 

 was a high average flow of 8.2 (4.9-1 3.1) liters per 

 min per m'-, whereas those in the older age group 

 had an average flow of only 2.1 (i. 5-3.5) liters per 

 min per m-. The relationship of the pulmonary blood 

 flow to age is shown in figure 23. It is apparent that 

 in patients with pulmonary hypertension (right 

 panel) the highest pulmonary flows occur in the 

 younger age groups (less than 12 years of age) and that 

 the flow decreases in late adolescence and in adult 

 life. 



The largest left-to-right shunts occurred in the 

 presence of low pulmonary resistance and gradually 

 decreased until the pulmonary resistance was similar 

 to systemic resistance. When the pulmonary resistance 

 exceeded that in the systemic vascular bed, the 

 predominant shunt was in the right-to-left direction 

 (fig. 24). 



In spite of the increased pulmonary flow seen in 

 most patients, systemic flow was within the range of 

 normal, the average flow being 4.1 (2.1-7.5) liters 

 per min per m-. 



Pulmonary-artery wedge pressures were obtained 

 in 16 of the patients studied. In all except one in- 

 stance these values were within the range for normal 



