Page 322 - Feline Cardiology

Chapter 21: Systemic Hypertension 331

SIGNALMENT organ damage, and incidental finding. Overt manifesta­
tions of end­organ damage (ocular or neurologic)
In the cat, systemic hypertension is secondary to an typically are identified as part of the chief complaint
underlying process such as chronic kidney disease or given by the owner. “Incidental finding” can refer to 1)
hyperthyroidism in the majority of cases. Therefore, the the discovery of a high systemic BP in a patient with a
signalment of patients with systemic hypertension is the disorder that is known to be associated with systemic
signalment of patients that have the primary diseases hypertension, 2) the discovery of a high systemic BP in
that cause it. In 58 hypertensive cats, mean age (13 ± 3.5 a patient without an identifiable underlying cause, or 3)
years) was significantly higher than in 130 normotensive the discovery of a lesion—rather than of hypertension
peers (9.6 ± 5.0 years) (Chetboul et al. 2003). No differ­ itself—where the lesion, such as an ocular abnormality
ences between males and females are apparent.
or left ventricular hypertrophy, is the first identified
abnormality, and both systemic hypertension and ulti­
HISTORY AND CHIEF COMPLAINT mately the underlying cause are found subsequently.
The historical findings associated with these categories
Because signs associated with hypertension­causing dis­ are addressed in turn in the following sections.
eases may be subtle or initially not apparent to owners,
obtaining a complete history is important and questions Overt Manifestations of Systemic
must be asked in a manner that does not deliberately Hypertensive Decompensation
lead to a desired answer and ultimately an erroneous Acute clinical signs attributable to systemic hyperten­
diagnosis of systemic hypertension. Common examples sion can involve the eyes, the central nervous system, the
of such a mistake include investigating the presence or heart, or the kidneys. Large retinal detachment, hyphema,
absence of polyuria and polydipsia, where questions and extensive retinal hemorrhages occur less often than
such as “Have the litterbox habits changed?” or “Are you pinpoint or multifocal retinal hemorrhages (Stiles et al.
aware of any decrease or increase in thirst?” are prefer­ 1994) but are more likely to cause the chief complaint
able to “Is he/she drinking and urinating more than of vision loss (Sansom et al. 1994;Stiles et al. 1994).
usual?”; another example is questions about lethargy, Blindness or impaired vision was a chief complaint in Systemic Hypertension
where “Have you noticed a change in his/her activity 2/15 (13%) of cats with chronic renal failure and sec­
level lately?” is more likely to elicit a useful answer than ondary systemic hypertension, for example (Stiles et al.
“Is he/she slowing down?” This nuanced history­taking 1994). Likewise, 8/58 (14%) of hypertensive cats in
is a further step away from misdiagnosis of white­coat another case series were blind, and 28/58 (48%) had
hypertension as “clinically significant” hypertension. ocular lesions (Chetboul et al. 2003). Systemic hyperten­
Specific aspects of the history that should be investi­ sion may be a very common cause of acute onset of
gated in cats thought or known to be hypertensive blindness or intraocular hemorrhage in general; of 16
include general demeanor, appetite, water consumption, cats referred for these problems, 11 (69%) were hyper­
urine production, and absence of vomiting (to identify tensive (13/15 with evidence of impaired renal function
signs of chronic kidney disease, hyperthyroidism, and and 1 hyperthyroid) (Sansom et al. 1994).
other causative disorders). For example, in a survey of Neurologic signs caused by systemic hypertension
58 hypertensive cats, a history of polyuria and polydipsia may consist of lethargy, ataxia, blindness, focal (and gen­
was present significantly more often in these cats (31/58, erally asymmetrical) deficits indicating an intracranial
53%) than in 113 normotensive peers (33/113, 29%) lesion, stupor, and seizures (Brown et al. 2005). These
(Chetboul et al. 2003). An owner’s observations of a cat’s signs have been described in association with herniation
bumping into objects, or of subtle or intermittent change of the brain during acute sustained systemic hyperten­
in eye color (iris, anterior chamber), may indicate mani­ sion (48–72 hours after onset of systolic BP reaching
festations of intraocular hemorrhage or other hyperten­ 198–234 mm Hg) in 2 cats (Brown et al. 2005); intracra­
sive ocular disorder. Similarly, disorientation, ataxia, nial arterial rupture (true hemorrhagic stroke), infarcts,
behavior change, or seizures may be caused by hyper­ and arteriolar spasm are other mechanisms by which
tensive encephalopathy or intracranial hemorrhage; a signs of intracranial disease can occur with systemic
rare differential diagnosis to consider in cats with these hypertension. The onset of neurologic signs in hyper­
signs is pheochromocytoma, which can cause systemic tensive cats generally carries a poor prognosis.
hypertension. Overt decompensation of the cardiovascular system
The clinician obtaining the history should take into (e.g., congestive heart failure [Wey and Atkins 2000],
account that systemic hypertension in cats presents in severe arrhythmia causing syncope, or thromboembo­
two different contexts: overt manifestations due to end­ lism) or the urinary system (e.g., acute renal failure) are