Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

150 Small Animal Radiolo g y and Ultrasono graphy
Fig. 2-125 A 1-year-old male mixed breed dog was
evaluated for exercise intolerance. A grade 5/6 systolic
heart murmur was present. A right parasternal
long-axis aortic outflow view reveals the presence of
a defect (*) in the interventricular septum (vs). The
origin (arrows) of the aorta (ao) is positioned astride
the interventricular septum. Also seen are the right
ventricle (rv), left ventricle (lv), and left atrium (la).
Diagnosis: Tetralogy of Fallot. The pulmonic stenosis
and right ventricular hypertrophy were seen on
other views.
with this physiologic change usually have large anatomical defects. Color-flow Doppler or
contrast (bubble) studies usually demonstrate the shunt flow. The right ventricular outflow
tract and main pulmonary arteries usually are dilated. If pulmonic valve insufficiency, secondary
to pulmonary hypertension, is noted, a regurgitant jet of less than 2.5 m/s fails to
support a diagnosis of pulmonary hypertension. 332
C O R T R I AT R I AT U M
Cor triatriatum is a rare anomaly in which there is a persistent remnant of a fetal membrane
in an atrium. This results in division of the atrium into two compartments,
which are connected by one or more openings. The openings may be very small and
may provide resistance to normal blood flow and result in congestion proximal to the
lesion.
Cor triatriatum sinister, involving the left atrium, has been reported in a cat with resulting
pulmonary congestion. 333,334 Cor triatriatum dexter, involving the right atrium, has
been reported in the dog and cat with resulting hepatic congestion and ascites. 335-344
The radiographic changes are limited to either pulmonary congestion or enlargement
of the caudal vena cava, hepatomegaly, and ascites. Two-dimensional echocardiography
reveals division of the atrial chamber and may document the presence of the obstructing
membrane.
AT R I O V E N T R I C U L A R VA LV E M A L F O R M AT I O N S
Atrioventricular valve malformation may affect the mitral valve, the tricuspid valve, or
both. Both dogs and cats may be affected. 345 The pathology may include an enlarged valve
annulus, short and thick valve leaflets, short and stout chordae tendineae, and upward malposition
of papillary muscles. 346 These changes result in valvular insufficiency.
M I T R A L A N D T R I C U S P I D I N S U F F I C I E N C Y
Mitral valve dysplasia causes mitral regurgitation and may result in subsequent left heart
failure. Radiographic findings of congenital mitral valve insufficiency, similar to those
associated with acquired mitral valve insufficiency, usually include massive left atrial
dilation and moderate to severe left ventricular enlargement. 347-349 Cardiogenic pulmonary
edema may be present if the dog is in left heart failure. Tricuspid dysplasia
results in tricuspid regurgitation and subsequently may lead to right heart failure.