Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

154 Small Animal Radiolo g y and Ultrasono graphy
A
B
Fig. 2-129 A 14-year-old neutered male Cairn Terrier with coughing. A grade
5/6 systolic murmur was present. A, A left parasternal four-chamber view reveals
dilation of the left atrium (la) and left ventricle (lv). The right ventricle (rv) and
right atrium (ra) are normal. The leaflets of the tricuspid valve (small arrow) are
normal. The leaflets of the mitral valve (large arrows) are shortened and grossly
thickened. The apparent discontinuity of the interatrial septum is due to artifact.
B, A right parasternal long-axis four-chamber view reveals left atrial (la)
and left ventricular (lv) dilation. There is mild prolapse of the thickened, irregular
septal leaflet of the mitral valve (arrow) into the left atrium. C, A right
parasternal short-axis view at the level of the mitral valve reveals the thickening
and irregularity of the mitral valve leaflets (arrows). The left ventricular outflow
tract (lvo) and right ventricle (rv) are also identified. Diagnosis: Mitral valve
insufficiency secondary to endocardiosis.
C
Although there is some correlation between the cardiac size and shape and the likelihood
that the dog will develop right- or left-sided heart failure or both, dogs with mild
degrees of cardiomegaly may develop congestive heart failure.
The echocardiographic findings are similar to those seen with congenital valvular
insufficiency. Specifically, there usually is dilation of the left atrium and left ventricle (Fig.
2-129). The M-mode study of the left ventricle usually will reveal increased fractional
shortening as the ventricle rapidly unloads into the low-pressure left atrium. Careful study
of the mitral valve leaflets frequently will reveal that they are shortened, thickened, and
irregular (Fig. 2-130). Nodular changes may be observed. If severe, prolapse of the mitral
valve leaflet into the left atrium also may be seen.
In unusual situations, a chordae tendineae may rupture and result in a flail leaflet effect
that is typified by the tip of the flail cusp extending into the left atrium in systole and then
displacing into the left ventricle in diastole. 377 Color-flow studies will reveal turbulent flow
across the valve and the regurgitant flow into the atrium. A subjective evaluation of severity
of regurgitation is possible by judging the degree, shape, and size of the regurgitant jet
relative to overall atrial size using multiple views. 378 Spectral Doppler studies can document
the peak velocity of flow (Fig. 2-131).
C A R D I O M YO PAT H Y
Dilated Cardiomyopathy. Canine dilated cardiomyopathy (DCM) most commonly
occurs in 2- to 7-year-old male large- and giant-breed dogs. 379-385 Specific causes have been
noted in some breeds. In some Great Danes an X-linked recessive genetic trait has been
identified. 386 In both English and American Cocker Spaniels, DCM may be associated with