References
Feline blood pressure measurement: when is it needed?
Abstract
Systemic hypertension is a common disorder, primarily affecting older cats. Most cases are secondary to underlying medical conditions, such as chronic kidney disease. If left untreated, systemic hypertension has the potential to cause serious damage to certain target organs and can be fatal. Target organs include the nervous system, cardiovascular system, eyes and kidneys. Target organ damage to the eyes is often pathognomonic and is detected on ophthalmological examination in up to 80% of cats with systemic hypertension. Blood pressure measurement is essential in confirming a diagnosis and should be prioritised in cats showing evidence of target organ damage. Blood pressure screening of apparently healthy older cats is justified, since the risk of hypertension increases with age. Systemic hypertension is diagnosed in cats with persistent elevation in their systolic blood pressure of 160 mmHg or higher. Stress and anxiety can cause a transient increase in systolic blood pressure so measurements should be collected in a manner that is as calm and ‘cat friendly’ as possible. In the presence of confirmed target organ damage, a single high systolic blood pressure reading confirms systemic hypertension. Where no target organ damage is detectable, evidence of elevated systolic blood pressure on two or more occasions is needed to confirm the diagnosis.
Systemic hypertension, a persistent increase in the systemic blood pressure above 160 mmHg systolic, is now commonly recognised in feline practice. There are several reasons for this, including an increased awareness of hypertension as a feline problem, increased access to diagnostic facilities and potentially, an increased prevalence of this condition related to the increasing age of the cat population – with current estimates of its prevalence at approximately 20% of cats aged 9 years and over (Conroy et al, 2018).
An age-related increase in systolic blood pressure has been reported (Bijsmans et al, 2015), meaning that older cats are at an increased risk of developing systemic hypertension. Its onset is also often associated with other conditions, many of which increase in prevalence with age, further increasing the risk to older cats. As an example, one study of 58 cats with systemic hypertension reported their mean age to be 13 years (Chetboul et al, 2003). The most commonly associated illnesses are chronic kidney disease and hyperthyroidism. Prevalence rates reported have been highly variable, for example, 20–65% of cats with chronic kidney disease are diagnosed with concurrent systemic hypertension, compared to 9–23% of newly diagnosed hyperthyroid cats (Kobayashi et al, 1990; Littman, 1994; Stiles et al, 1994; Syme et al, 2002; Syme and Elliott, 2003; Morrow et al, 2009; Williams et al, 2010). Other diseases that have been associated with hypertension in cats include primary hyperaldosteronism (Conn's syndrome), phaeochromocytoma, therapy with erythrocyte stimulating agents and occasionally, hyperadrenocorticism (Patnaik et al, 1990; Henry et al, 1993; Chun et al, 1997; Cowgill et al, 1998; Ash et al, 2005; Javadi et al, 2005; Calsyn et al, 2010; Wimpole et al, 2010; Brown et al, 2012; Chalhoub et al, 2012).
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