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12

Congenital Heart Disease
Merrilee Holland

Department of Clinical Sciences, College of Veterinary Medicine, Auburn, AL, USA

12.1 Tricuspid and Mitral Dysplasia involves a right ventricular location or “high” defect, which
is best imaged from a right parasternal short axis view at
Tricuspid and mitral dysplasia are the most common con- the heart base. At this location, a small defect is difficult to
genital heart diseases in cats. Tricuspid dysplasia can be visualize and color Doppler is needed for detection. The
seen alone or concurrently with mitral dysplasia in up to shape of the aorta is altered and may appear flattened or
23% of cats. Radiographic changes associated with tricus- conical dorsally. Radiographic findings are dependent on
pid dysplasia are dependent on the severity of the malfor- the size of the defect; the thoracic radiographs could be
mation and involve the right side of the heart. Radiographic normal. If significant left‐to‐right shunting occurs across
evidence of progression to right heart failure includes the defect, primarily left atrial and ventricular enlargement
dilation of the caudal vena cava, pleural effusion, and along with pulmonary over circulation will be present. The
variable development of ascites (Figure 12.1). aorta, pulmonary artery, and cranial and caudal vena cava
The echocardiographic changes are variable, with thick- do not respond identically, so it is crucial to evaluate all
ening of the valve, abnormal attachment sites, and four sets of pulmonary vessels for changes.
shortening of the leaflets. The earliest cardiac finding is The echocardiographic findings can assist in determina-
abnormality in tricuspid valve (TV) structure consistent tion of the prognosis, with the size of the defect relative to
with right atrial enlargement. Profound right atrial enlarge- the size of the aorta of less than 40%, velocity across the
ment can be seen with this defect (Figure 12.1) [1]. defect >4.5 m/s, no significant aortic insufficiency, and low
Mitral dysplasia can have nonspecific radiographic signs right ventricular pressures [2].
of left heart enlargement, pulmonary venous congestion,
pulmonary edema, and pleural effusion. Echocardiographic 12.3 Atrial Septal Defect
findings are left atrial enlargement and variable degree of
left ventricular hypertrophy due to volume overload, which
may progress to left heart failure (Figures 12.2–12.4) [1]. Atrial septal defects (Figure 12.8) account for about 9% of
all congenital heart disease in cats [2]. Malformation of the
defect below the level of the foramen ovale near the atrio-
ventricular valves is the most common site in cats.
12.2 Ventricular Septal Defect Radiographic findings are variable, dependent on the size
of the defect, and include biventricular cardiomegaly, pul-
Ventricular septal defects (Figures 12.5–12.7) are relatively monary overcirculation, and, with heart failure, pulmo-
common in cats, occurring in about 15% of congenital nary edema. The best imaging plane is a right parasternal
heart defects. The defects can be seen in the perimembra- long axis view for evaluation of this defect. Because echo
nous portion of the interventricular septum (IVS) just dropout occurs normally at the foramen ovale, color and
below the TV, which can best be visualized from a right spectral Doppler studies must be used to document blood
parasternal long axis four‐chamber view. A second site flow across the defect [1,2].

Feline Diagnostic Imaging, First Edition. Edited by Merrilee Holland and Judith Hudson.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.