Page 267 - Clinical Small Animal Internal Medicine

24 Congenital Heart Disease 235

Epidemiology commonly in female dogs, with a 3:1 female predomi-
VetBooks.ir The prevalence of CHD in the dog and cat is difficult to nance. Pulmonary valve stenosis has not been recog-
nized as having gender predominance except in the
English bulldog, where males are more commonly
quantify due to a lack of routine perinatal care, occurrence
of conditions that are not apparent on routine physical afflicted than females. A male predominance for TVD
examination, and hospital biases in published reports. has also been reported in the veterinary literature. In the
The work of Detweiler and Patterson in the Philadelphia cat, a male predominance has been suggested for atrio-
area suggested a CHD prevalence rate of 0.56% among ventricular valve malformation, aortic stenosis, and
5000 dogs surveyed in the mid‐twentieth century, while tricuspid valve dysplasia.
Buchanan found a rate of 0.67% for all dogs presented to
the University of Pennsylvania between 1987 and 1989. Breed
While the true prevalence of CHD in dogs and cats is
unknown, there are data available evaluating the relative Numerous breed predilections have been reported for
incidence of specific malformations in each species. The animals with CHD, particularly dogs. Table 24.1 shows a
author compiled data from several studies in an attempt listing of common defects and the breeds known or sus-
to summarize the relative prevalence of CHD in small pected to have an increased prevalence of each defect.
animals. Ten applicable studies of CHD prevalence in This table should not be considered authoritative or
dogs were found in the veterinary literature, comprising a exhaustive, as spontaneous defects can occur in any breed
sum of 4694 defects. When totaled, PDA (26%), SAS at any time. Additionally, the incidence of CHD will likely
(24%), and PS (22%) were the most common and of nearly change as breed populations continue to evolve. In the
equal incidence. As such, these three diseases should be cat, few breed predilections are recognized other than
highest on a practitioner’s differential list when listening endocardial fibroelastosis, which is reported to have a
to a puppy with a loud heart murmur; other congenital higher prevalence in Burmese and Siamese breeds.
malformations of the heart are less common.
There are fewer data available about CHD prevalence
in the cat. When evaluating several studies of CHD prev- History and Clinical Signs
alence in cats, five studies covering 435 defects can be
found. Ventricular septal defect appears to be the most Animals with complex defects or severe CHD may pre-
common defect in the cat, comprising over 18% of cases. sent within the first days to weeks of life due to failure to
PDA is not generally considered a common disease in thrive, dyspnea, cyanosis, or syncope. It is likely that
the cat, compared to the dog, but was noted in over 11% most puppies and kittens with severe cardiac malforma-
of defects. Dysplasia of the atrioventricular valves (mitral tions die early in life and prior to veterinary examination.
or tricuspid) each accounted for an additional 10% of The common history for dogs and cats with CHD is that
defects. Feline CHD, therefore, should be considered of an asymptomatic pet with an appointment for a well-
distinct from and with a different incidence of common ness exam, deworming, and vaccination. Auscultation
defects than canine CHD. Semilunar valve disease during the physical examination of these patients is often
(PS and SAS) is exceedingly rare in cats. the first and earliest clue that CHD may be present – as
such, careful and thorough examination of all young ani-
mals is advised.
Signalment

Age Diagnosis
Most animals with CHD present at a young age. However,
adult animals with undiagnosed CHD may present later Auscultation
in life and often as a result of complications (heart fail- Screening for congenital cardiac disease typically begins
ure, syncope, or cyanosis) from their cardiovascular dis- with a thorough physical examination performed at the
order if it was not detected at an earlier age. first general health examination. Auscultation is impera-
tive for screening of CHD as the most common forms of
CHD typically present with a systolic (SAS, PS, VSD,
Sex
TVD) or continuous (PDA) murmur. Auscultation in
Both sexes are commonly afflicted with CHD, though puppies and kittens should be performed in a quiet room
sex predilections for some specific conditions have with appropriate restraint and sufficient time devoted to
been identified. PDA has been reported to occur more a thorough examination.