Page 127 - Feline Cardiology

126 Section D: Cardiomyopathies

therapy that has reduced vessel size but not yet resolved
pulmonary edema or pleural effusion, interindividual
variation in vessel size irrespective of heart failure,
patient positioning (DV versus VD views), or pulmo-
nary edema obscuring visualization of the vessels. There
is no particular pattern of pulmonary edema distribu-
tion in cats with heart failure, unlike dogs that typically
have a perihilar to caudodorsal distribution of pulmo-
nary infiltrates. Presence of ascites along with pleural
effusion virtually eliminates HCM as a cause of the fluid
Cardiomyopathies involving the right heart such as dilated cardiomyopa-
A
accumulation and raises suspicion of cardiac diseases
thy, unclassified cardiomyopathy, tricuspid valve dyspla-
sia, or arrhythmogenic right ventricular cardiomyopathy,
or noncardiac disease (feline infectious peritonitis,
malignancy, etc.).

Echocardiogram (see also Chapter 7)

Key Points

• Echocardiography is the essential tool to diagnose
HCM in cats, and it allows accurate assessment of
chamber enlargement, quantification of concentric
hypertrophy, evaluation of the source of a murmur,
assessment of myocardial systolic and diastolic function,
and assessment of whether there is spontaneous
echocardiographic contrast or an intracardiac thrombus.
• LV concentric hypertrophy is defined as end-diastolic
B left ventricular septal or free wall thickness of 6 mm
or greater. Measurement of LV wall thickness by the
Figure 11.8. Thoracic radiographs of a cat with severe hyper- 2-dimensional technique has largely replaced the M-
trophic cardiomyopathy and congestive heart failure. This cat has
mode technique, because M-mode can underestimate
typical radiographic changes indicative of severe pulmonary ede- or miss segmental wall thickening, which is common in
ma and pleural effusion. Although the cardiac silhouette is par-
cats with HCM; unlike M-mode, there is no limitation
tially obscured by the pleural effusion on the lateral view, there of cursor placement when measuring wall thickness
is suggestion of cardiomegaly and pulmonary venous distension
using the 2-dimensional method. This is important when
(blue arrow) at the hilus. The cardiac silhouette is completely ob- measuring asymmetric or segmental hypertrophy.
scured by pleural effusion on the dorsoventral view, but pulmo-
• Left atrial size can be measured by 2-dimensional
nary vascular distension is seen as well as the mixed pattern of and M-mode methods, and left atrial enlargement is
pulmonary edema and pleural effusion. Echocardiography is an
considered to be present when the left atrial diameter to
important tool to confirm that severe heart disease is present, aortic diameter ratio is ≥1.5.
consistent with the pulmonary infiltrates and pleural effusion be-
• Identification of normal left atrial size in cats with HCM
ing caused by congestive heart failure. Red arrow = caudal lobar that also have pulmonary infiltrates or pleural effusion
pulmonary artery; blue arrow = caudal lobar pulmonary vein de-
and no known inciting trigger such as intravenous fluid
picted on the right side of the thorax on the dorsoventral view; administration virtually eliminates left-sided congestive
the pulmonary vein on the left side of thorax is unaltered.
heart failure as the diagnosis.
• SAM of the mitral valve can be identified on
2002). Pulmonary venous distension is another radio- 2-dimensional echocardiography from the right
graphic abnormality that occurs when there is elevated parasternal long-axis left ventricular outflow tract view.
left atrial pressure and is usually present in heart failure, Color-flow Doppler shows the characteristic double
turbulent jet of mitral regurgitation and turbulence
but absence of pulmonary venous distension does not in the left ventricular outflow tract arising from the
rule out heart failure. Reasons for absence of pulmonary common point of the anterior mitral leaflet obstruction.
venous distension on radiographs may include diuretic