Page 209 - Feline diagnostic imaging

212 13 Acquired Heart Disease
patients with hyperthyroidism, the left ventricular septum was found in the group with systemic hypertension. The
and free wall are thickened with variable enlargement of size of the aorta was increasing larger beginning at the aor­
the left atrium (Figure 13.10c,d). Typically, the left ventri­ tic valve and extending to the proximal ascending aorta
cle in these patients are hypercontractile. If untreated, car­ when imaged from a right parasternal long axis view in the
diac failure can appear similar to other conditions resulting hypertensive cats compared to the normal group. The ratio
in dilation of the right and left ventricle and biatrial of the left atrium to the aorta in the hypertensive group was
enlargement [2]. Following treatment for hyperthyroidism, similar to the control group [15].
when cats were reexamined in 4–21 months, left ventricu­ In a different study of 19 hypertensive cats, 14/19 had
lar hypertrophy had improved or resolved and fractional thickening of the interventricular septum and left ventric­
shortening decreased. In some of the cats, not all of the ular free wall, and enlargement of the left atrium compared
cardiac changes resolved, suggesting an underlying cardio­ to 79 normal cats (Figures 13.13–13.16) [13]. Another study
myopathy or thyrotoxic damage (Figure 13.11) [10]. evaluating 188 cats with presenting signs of systemic
In a different study which examined 91 cats before and hypertension documented hypertension above 170 mmHg
after treatment of hyperthyroidism with radioiodine, a in 58 of these cats. Echocardiographic findings in 39 of the
small number had an enlarged left ventricular chamber 58 cats with hypertension revealed thickening of the inter­
during diastole and systole prior to treatment, which ventricular septum and left ventricular free wall with a
may be related to a thyrotoxic state leading to heart fail­ decrease in the size of the left ventricular chamber in dias­
ure. Similar changes were noted in the left ventricular tole [14].
wall of these cats before and after treatment; however, an
increase in left ventricular chamber in systole was seen
post treatment with a decrease in the fractional shorten­ 13.6 Volume Depletion/Volume
ing [11]. Interestingly, cats managed medically can have Overload
normal echocardiographic parameters on presentation
(Figure 13.12). Volume depletion will significantly alter the appearance of
the interventricular septum, left ventricular free wall, and
left ventricular chamber in systole and diastole
13.5 Systemic Hypertension (Figure 13.17). The walls of the left ventricular chamber
will be increased and the left ventricular chamber will be
According to the ACVIM consensus statement, systemic decreased.
hypertension describes the risk for future damage to target The interventricular septum and free wall of the left ven­
organs based on the elevation of the systolic and diastolic tricle measured thicker than normal (>6 mm) in 4/10 cats
blood pressure. Systolic blood pressure less than 150 is a in one study while dehydrated. The size of the left atrium is
level 1 risk, 150–159 level 2, 160–169 level 3, and >170 level key to differentiating “real” hypertrophy of the left ventric­
4. Target organs damaged by the increased sustained level ular walls from volume depletion. In induced volume
of blood pressure include the kidneys, eyes, brain, and car­ depletion of 7–10%, the left atrial size will be similar or
diovascular organs [12]. Hypertension can be idiopathic, smaller than the aorta (Figure 13.17). Once these cats were
primary, or secondary to chronic renal failure, hyperthy­ given intravenous fluids at a maintenance rate 2.5–3 mL/
roidism, HCM, diabetes, and acromegaly [13,14]. kg/h, the left atrial size increased and the left ventricular
The wavy or undulating shape of the aorta was the most chamber remained unchanged in diastole but decreased in
consistent radiographic finding in patients with systemic systole, resulting in an increase in fractional shortening.
hypertension best visualized on the lateral projection [15]. When the fluid rate was increased to 10 mL/kg/h, 6/10 cats
In addition, on the ventrodorsal image, the ascending aorta developed a systolic murmur and increased size of the left
can be seen projecting cranial to the cardiac silhouette and ventricular chamber in diastole without a change in systole
should not be mistaken for a soft tissue mass (Figure 13.3). producing an increase in the fractional shortening. The left
On the ventrodorsal image, the proximal descending aorta atrial size increased significantly in size, resulting in the
may bow laterally with systemic hypertension. ratio of the left atrium to aorta above the normal of 1.5 [16].
Echocardiographic findings in a study involving 15 When evaluating for volume depletion, the size of the left
hypertensive cats included hypertrophy of the interven­ atrium will be similar or smaller in size compared to the
tricular septum and left ventricular free wall as compared aorta when assessing from a right parasternal short axis
to 15 normal patients. A trend of focal hypertrophy of the view at the heart base. It is possible to misdiagnose patients
interventricular septum in the left ventricular outflow tract with cardiac disease due to alternations in wall thickness