Page 129 - Feline Cardiology

128 Section D: Cardiomyopathies

RV
IVS

LV
Cardiomyopathies A LVFW

Figure 11.10. M-mode echocardiogram of the left ventricle of
a cat with moderate hypertrophic cardiomyopathy. The cursor is
positioned at the 12 o’clock position of the interventricular sep-
tum and the 6 o’clock position between the papillary muscles at
the left ventricular free wall. This M-mode echocardiogram shows
increased end-diastolic left ventricular wall thickness of the inter-
ventricular septum (IVS) and left ventricular free wall (LVFW), and
hyperdynamic wall motion with a fractional shortening of 78%.
Papillary muscle interference is indicated with an asterisk.

septum and the left ventricular free wall are measured.
If an ECG is not present, subjective assessment of end-
B
diastole is made by scrolling through the cine-loop and
looking for the frame with the largest left ventricular
internal diameter at end-diastole. By convention, the
measurement is made immediately prior to atrial con-
traction (mechanical atrial systole), meaning that the
measurement is made at the end of diastasis (passive
ventricular filling) and the final, brief excursion of the
ventricular walls caused by atrial contraction is not mea-
sured. M-mode can also be used to measure left ven-
tricular wall thickness, but there are limited choices of
M-mode cursor positions (Figure 11.10). Often papil-
lary hypertrophy may obscure the ability to carefully
define the endocardial surface of the left ventricular free
wall to measure. Steerable M-mode has advantages over
C
traditional fixed M-mode because the cursor placement
Figure 11.9. Two-dimensional echocardiogram of the left ven- can be adjusted depending on the location of the great-
tricle of a normal cat and a cat with moderate to severe hyper- est wall thickness. Some cats with HCM have global
trophic cardiomyopathy. This end-diastolic frame from the right symmetrical concentric hypertrophy, whereas most have
parasternal short-axis view at the level of the papillary muscles asymmetrical hypertrophy. For example, some cats have
of a normal cat depicts normal wall thickness and no papillary only interventricular septal hypertrophy (Figure 11.11),
muscle hypertrophy (A) in comparison to a cat with HCM (B). The whereas others have hypertrophy of solely the left ven-
cat with HCM has mild to moderate concentric hypertrophy of the tricular free wall or papillary muscles. The basilar inter-
left ventricle, with an end-diastolic interventricular septal thick- ventricular septum should be measured from the right
ness (IVSd) of 6.6 mm, and a left ventricular free wall thickness at
end-diastole of 7.3 mm. There is moderate papillary muscle hy- parasternal long-axis 4-chamber or left ventricular
pertrophy and hyperechogenicity (*). The end-systolic frame from outflow tract view, as it may provide the best visualiza-
the same cat as in (B) shows end-systolic cavity obliteration (C). tion and measurement of the thickest part of the basilar