Page 327 - Feline Cardiology

336 Section I: Systemic Hypertension

acceptable for clinical decision­making in systemic Interestingly, this group of cats included some in
hypertension suspects. which thickening of the left ventricle was noted to be
asymmetrical. This finding is counterintuitive: a uniform
Ancillary Tests: Clinical Pathology increase in afterload (increased BP) should give rise to
Routinely, a complete blood count, serum biochemical diffuse, symmetrical ventricular hypertrophy, but such
profile, and urinalysis are indicated in cats being evalu­ asymmetry has been observed in human hypertensive
ated for, or known to have, systemic hypertension. patients. Regrettably, this study did not follow these cats
Follow­up testing is performed based on results of pre­ through treatment and a prolonged normotensive
vious tests and findings in the history and physical exam. period to document regression of hypertrophy. Without
No abnormalities are specific to systemic hypertension this information, hypertensive left ventricular hypertro­
in cats, although proteinuria is a common finding phy with simultaneous hypertrophic cardiomyopathy
(increased intraglomerular pressure, glomerular damage cannot be excluded, and this combination occurs with
as part of chronic kidney disease). Azotemia with isos­ some regularity in cats. With regards to other echocar­
thenuria is consistent with kidney disease; hyperphos­ diographic findings, hypertensive cats also show dilation
phatemia and/or anemia may also be present. Cats age of the proximal aortic root and adjoining segments of
6 years old or older should have serum thyroxine levels the proximalmost aorta. These changes are significantly
measured to rule out hyperthyroidism. Retroviral serol­ different from equivalent measurements in normoten­
ogy is assessed as indicated by environmental exposure sive cats (Nelson et al. 2002). Some hypertensive cats
and clinical information. may develop eccentric left ventricular hypertrophy
(dilation with preserved/enhanced contractility), and
these cats may be younger and more hypertensive than
Ancillary Tests: Thoracic Radiographs their counterparts (Chetboul et al. 2002). More recent
Systemic Hypertension systemic hypertension, and they are an insensitive test have identified evidence of systolic and diastolic dys­
There are no pathognomonic radiographic findings of
echocardiographic techniques (tissue Doppler imaging)
for this disorder. Nevertheless, some characteristic find­
function of the longitudinal left ventricular myocardial
ings are associated with systemic hypertension and
fibers in hypertensive cats with left ventricular hypertro­
should be recognized. Undulation or tortuosity of the
phy (Carlos Sampedrano et al. 2006)
descending thoracic aorta has been associated with sys­
temic hypertension (Nelson et al. 2002) (see Chapter 7,
Figure 7.2). Cardiomegaly is not generally observed; the Ancillary tests: Abdominal Ultrasonography
An abdominal ultrasound examination is warranted if
modest degree of left ventricular hypertrophy, and the elements of the physical exam and diagnostic testing to
concentric nature of that hypertrophy, probably explain date suggest a case where chronic kidney disease is com­
the lack of difference in cardiac size in 15 hypertensive plicated (e.g., concurrent pyelonephritis, renal lym­
cats compared to 15 matched controls (Nelson et al. phoma, polycystic kidney disease, perirenal pseudocyst,
2002). hydronephrosis) or where adrenal disease is possible
based on clinical features, mass effect in the adrenal
Ancillary Tests: Echocardiography region on physical exam, or radiographs (e.g., suspect
Echocardiography is commonly performed in cats that pheochromocytoma because of intermittent or sus­
are suspected or known to be hypertensive. In one study tained ventricular tachycardia; intermittent disorienta­
of 171 cats referred for BP measurement, a heart murmur tion, anxiety, or flushing; markedly fluctuating BP), or
was present in 117 (68%), potentially leading to a rec­ suspected primary aldosteronism based on profound,
ommendation of echocardiography. Echocardiographic severe, refractory hypokalemia (serum K+ often
findings in hypertensive cats include left ventricular <2.5 mEq/dl despite aggressive replacement therapy).
concentric hypertrophy (left ventricular thickening),
which is generally mild. For example, 15 hypertensive TREATMENT
cats had a median left ventricular free wall diastolic
thickness of 5.1 mm, which was mildly but significantly General
(P = 0.02) greater than 4.2 mm in 15 normotensive cats An elevated arterial BP does not immediately warrant
(Nelson et al. 2002). Hypertension­associated left ven­ treatment. Environmental stressors that can transiently
tricular hypertrophy is reversible over months with elevate BP must first be identified and abolished, and a
adequate reduction in BP (target systolic BP < 160). Left true diagnosis of systemic hypertension can then be
ventricular hypertrophy is not a prognostic indicator in confirmed. Second, steps must be taken to control dis­
hypertensive cats. eases that cause systemic hypertension. Third, antihy­