Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

144 Small Animal Radiolo g y and Ultrasono graphy
Fig. 2-117 A 3-year-old spayed
female English Bulldog with ascites
and a grade 5/6 systolic heart murmur
that was best heard over the left
heart base. A right parasternal shortaxis
view reveals narrowing of the
valvular orifice (*). There is a dilation
(D) of the main pulmonary
artery (pa) distal to the narrowing.
Other structures noted are the aorta
(ao), right ventricular outflow tract
(rvo), pulmonary artery (pa), right
pulmonary artery (rpa), and left pulmonary
artery (lpa). Diagnosis:
Pulmonic stenosis.
Fig. 2-118 A 1-year-old neutered
female mixed breed dog had an
asymptomatic grade 4/6 heart murmur
heard best at the left cranial cardiac
base and radiating to the right
thorax. A continuous wave Doppler
study across the pulmonic valve
reveals an increased pulmonic valve
velocity (velocity of 3.7 meters per
second and a 55 mm Hg gradient)
that “wraps around” due to inadequate
settings for total velocity and
level of the baseline. Also present is a
significant pulmonic insufficiency
(velocity of 1.6 meters per second).
Diagnosis: Moderate pulmonic
stenosis and insufficiency.
apparent (Fig. 2-117). Thickened, domed pulmonic valves also may be seen. In one study,
valve morphology was grouped into two forms: type A—normal annulus diameter and
aortic-to-pulmonary ratio 1.2. The dogs in the B group were mostly brachycephalic breeds.
Dogs with type B valve morphology had fewer favorable outcomes with balloon valvuloplasty.
318 As a result of the stenosis, right ventricular hypertension may lead to thickening
of the right ventricular free wall and interventricular septum, which can be identified
by echocardiography. The right ventricular diameter may be increased. The normal
motion of the interventricular septum may be dampened. If severe, the increased right
ventricular pressures may cause paradoxical septal motion, a condition in which the
interventricular septal motion parallels that of the left ventricular free wall due to pressure
overload in the right ventricle, nearly obliterating any fractional shortening and
severely reducing stroke volume.
Doppler studies are used to estimate the pressure gradient across the valve, which aids
in choosing between medical and surgical treatments (Figs. 2-118 to 2-120). Color-flow