994 
ANIMAL DISEASES 
Figure 1. — Patent ductus arteriosus with left-to-right shunt. Left: Left lateral aortic angiogram of a 12-week-old 
male mixed Poodle with a large funnel-shaped PDA and left-to-right shunt. After injection of contrast medium 
into the aorta (A), the ductus arteriosus (D) and dilated pulmonary artery (P) were visualized. The opposed 
walls of the ductus arteriosus and aorta are seen as a radiolucent line (arrows). Right: Left lateral view of the 
heart of 16-week-old female Poodle with a large funnel-shaped PDA (D) ; a left-to-right shunt was present 
in life. 
Reprinted from reference #5 by permission of the American Heart Association, Inc. 
size of the ductal lumen in pups with patent 
ductus arteriosus varied from a small channel 
of little hemodynamic significance to a large 
vessel approaching the diameter of the ascend- 
ing aorta. In pups vi^hich had large ductal lu- 
mens, there was a high incidence of left heart 
failure and a smaller incidence of severe pul- 
monary hypertension with right to left or bi- 
directional shunts. The incidence of these seque- 
lae to PDA rose from 33% in pups receiving 
50% or less of their genomes from dogs with 
PDA, to 78% in pups whose parents both had 
PDA.^ This finding is consistent with the view 
that the genes predisposing to PDA have a dose 
related eff'ect on the eventual size of the lumen 
in ductuses which fail to close. 
Observations on the natural history of left 
heart failure and pulmonary hypertension in 
pups with hereditary PDA have led to some in- 
teresting evidence regarding the pathogenesis 
of these two sequelae, evidence which may aid 
in understanding the factors influencing these 
serious complications of congenital heart dis- 
ease in young children. Daily examinations of 
the offspring of dogs with PDA have shown 
that PDA can be detected in some individuals as 
early as the second day after birth and that 
most. affected pups are recognizable by the end 
of the second week.'^ A high incidence of left 
heart failure occurs between the second and 
fifth week, preceeded by auscultatory, radi- 
ographic, and electrocardiographic signs of an 
increasing left to right shunt with left ventricu- 
lar overloading. Pups with the syndrome of left 
heart failure invariably die with severe pulmo- 
nary edema before the end of the fifth week un- 
less surgical ligation of the ductus arteriosus is 
carried out. If signs of left heart failure did not 
become clinically evident by the fifth week, the 
animals usually survived to adulthood. 
These observations suggest that the second 
through the fourth week of postnatal life is a 
period of critical circulatory adjustment in the 
dog, during which a downward changing pul- 
