Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

Chapter Two The Thorax 141
Fig. 2-113 A 6-month-old male
Rottweiler with a grade 4/6 systolic
ejection-type murmur that was best
heard at the left heart base. A, A right
parasternal long-axis aortic outflow
view revealed the left ventricle (lv)
and aorta (ao). B, A close-up view of
the aortic outflow tract revealed a
focal hyperechoic band (arrows) narrowing
the left ventricular outflow
tract (lvo) immediately beneath the
aortic valve leaflets. Diagnosis:
Aortic stenosis.
A
B
A
Fig. 2-114 A, An M-mode view at the level of the left ventricle reveals the normal structures: interventricular
septum (vs), left ventricular cavity in diastole (lvd), left ventricular cavity in systole (lvs),
and left ventricular free wall (lvw). The fractional shortening (LVED – LVES / LVED) is increased
(approximately 55%). B, An M-mode view at the level of the mitral valve reveals abnormal valve
motion with systolic anterior motion of the septal leaflet (sam). Also defined are the E-point (e) and
A-point (a). Diagnosis: Systolic anterior motion of the mitral valve and increased fractional shortening
consistent with aortic stenosis.
B
with a broad apex due to the left ventricular enlargement. The remainder of the heart and
thoracic structures usually are normal.
Echocardiographic findings may be specific for the site of anomaly. Subvalvular
aortic stenosis may be seen either as a discrete membrane or focal ridge just below the
aortic valve, or as a more elongated, tunnel-type narrowing of the left ventricular outflow
tract (Fig. 2-113). Usually, this is most noticeable on the septal side. Other findings
associated with subvalvular aortic stenosis may include hypertrophy of the left ventricle,
a hyperechoic subendocardium, normal to increased fractional shortening, coarse
systolic fluttering of the aortic valve, partial premature closure of the aortic valve, and
thickening of the septal leaflet of the mitral valve with or without systolic anterior
motion of the septal leaflet of the mitral valve toward the interventricular septum in
early systole (Fig. 2-114). Systolic anterior motion can be so severe (prolonged) that the
septal leaflet of the mitral valve opens wide in midsystole into the aortic outflow tract
and acts as a partial aortic outflow obstruction. Although the poststenotic aneurysmal
dilation of the aorta can be seen, the degree of aneurysmal dilation is variable and may
not be readily noted on echocardiography. Valvular stenosis is difficult to identify. In
this condition, the valve leaflets may appear thickened, with a decreased range of
motion. Supravalvular lesions are very rare but would show an obvious constriction distal
to the aortic valve.