992 
ANIMAL DISEASES 
Table I. — Comparison of the Relative Frequencies of 
Various Types of Cardiovascular Malformations in 
Human and Veterinary Clinics 
Percent of all Heart Defects 
Dog" 
Dog3 
Human" 
Malformation 
Veterinary 
Clinics-NCI 
Survey (N— 
TT r,f P 
U. OI Sr. 
Veterinary 
Clinic 
303) (N = 289) 
Children's 
Clinics 
(N = 8674) 
Patent Ductus Artreiousus 
31.0 
25.3 
14.9 
Pulmonic Stenosis 
13.5 
17.6 
10.5 
Aortic Stenosis 
3.0 
12.3 
5.6 
Ventricular Septal Defect 
9.2 
6.2 
24.2 
Atrial Septal Defect 
3.0 
3.7 
12.4 
Tetralogy of Fallot 
* 
3.4 
10.9 
Subtotal 
59.7 
68.6 
78.5 
Persistent Right Aortic Arch 10.9 
7.1 
* 
Coarctation of Aorta 
0.0 
0.0 
4.9 
Other 
29.4 
24.4 
16.6 
Total 
100.0 
100.0 
100.0 
* Frequency not given — included in "Other." 
tricular septal defect, atrial septal defect, and 
tetralogy of Fallot. Ventricular septal defect 
was the most commonly diagnosed lesion in the 
human series, followed by patent ductus arter- 
iosus. In both dog studies, patent ductus arter- 
iosus was the most commonly diagnosed defect, 
while pulmonic stenosis was the next most com- 
mon. There are two obvious differences between 
dog and man in their susceptibilities to particu- 
lar anatomic defects. Coarctation of the aorta is 
only slightly less common than the 6 most fre- 
quently reported malformations in man, but it 
was not observed in either veterinary clinic 
population survey. A recent report constitutes 
the only documented occurrence of aortic coarc- 
tation in a dog.i- Persistent right aortic arch 
as an isolated malformation is found much 
more frequently in the dog than in man as is in- 
dicated by the surveys in Table I and a review 
of the veterinary literature.'* 
ETIOLOGY OF CARDIOVASCULAR 
MALFORMATIONS IN THE DOG 
Studies of the breed distribution of cardio- 
vascular malformations in dogs presented to the 
University of Pennsylvania Veterinary Clinic 
suggested that purebred dogs are more suscep- 
tible to these birth defects than are dogs of 
mixed breeding, the prevalence rate being ap- 
proximately three times greater in purebreds 
than in mongrels.^-^ This finding has been con- 
firmed by Mulvihill in an independent survey of 
10 other university veterinary clinics partici- 
pating in a Veterinary Medical Data Program 
conducted by the National Cancer Institute." 
In both the University of Pennsylvania and 
National Cancer Institute surveys, there was a 
non random distribution of anatomic defects 
among the breeds, suggesting that certain 
breeds are more susceptible to some defects 
than others.^''" Breed predispositions sug- 
gested by the two veterinary clinic population 
surveys and a review of the world literature* 
are given in Table II. 
The apparent predisposition of certain breeds 
to specific anatomic defects is consistent with 
the hypothesis that the underlying abnormali- 
ties in development are caused at least in part 
by lesion-specific genetic determinants concen- 
trated in these breeds.^'^ The higher preval- 
ence rate of congenital heart defects in pure- 
bred than mixed dogs further suggests that 
these genetic determinants may be single genes 
or polygenic sets that behave as recessives. 
Tests of the hypothesis of lesion-specific ge- 
netic determinants have been conducted in a 
breeding colony of dogs with congenital heart 
disease.35.*5.7 Affected animals were obtained 
for the colony through the cooperation of own- 
ers, kennels, and veterinarians. Young animals 
were raised to maturity and used in test mat- 
ings. Initial tests involved the mating of af- 
fected pairs, matched for lesion and breed ac- 
cording to the suspected breed predispositions 
(Table II). In this way, the highest probability 
Table II. — Breed Predispositions to Congenital Heart 
Defects Suggested by Epidemiologic Data and Litera- 
ture Review 
Defect 
Breed 
Source 
Patent ductus arteriousus 
Poodle 
3, 14 
Collie 
3 
Pomeranian 
3 
Cocker Spaniel 
14 
Pulmonic stenosis 
English Bulldog 
3 
Fox Terrier 
3 
Chihuahua 
3 
Beagle 
3 
Aortic stenosis 
Boxer 
3, 4, 14 
German Shepherd 
3 
Newfoundland 
3 
Ventricular septal defect 
Siberian Husky 
14 
Persistent right aortic arch 
German Shepherd 
3, 4, 14 
Irish Setter 
3 
Tetralogy of Fallot 
Keeshond 
3 
