American Association of Feline Practitioners

Veterinary professionals passionate about the care of cats

Classification

Systemic hypertension is defined as a sustained increase in systolic blood pressure (SBP) and is categorized as idiopathic, secondary, or situational.

Idiopathic Hypertension 

  • Persistent pathological hypertension in the absence of any identifiable underlying causes
  • Accounts for approximately 13%-20% of cases in cats
  • Need to rule out underlying conditions
    • Increased BP may induce polyuria (pressure diuresis), producing a low urine specific gravity (USG) <1.030, making it difficult to rule out kidney disease as an underlying cause
    • Approximately 12% of nonazotemic, nonhyperthyroid cats were hypertensive in one study

    • In another study, 7% of 133 apparently healthy initially normotensive cats >9 years developed idiopathic hypertension

Secondary Hypertension

  • Persistent pathological hypertension concurrent with a disease or condition known to cause hypertension OR hypertension associated with the administration of a therapeutic agent or ingestion of a toxic substance known to cause increased BP
  • Hypertension may persist even after effective treatment of the primary condition is initiated
  • If primary condition is resolved by therapeutic intervention, institute serial follow-up evaluations
  • Cats often have more than one condition, so complete evaluation for other causes is necessary
  • Chronic Kidney Disease (CKD)
    • Most common condition associated with hypertension
    • Azotemia has been reported in up to 75% of hypertensive cats
    • Between 19%-65% of cats with CKD have been found to be hypertensive
    • Prevalence and severity of hypertension does not appear to be related to severity of CKD
    • Cats with congenital kidney insufficiency may have normal serum creatinine and BUN levels but decreased USG
    • Exact pathogenesis is not completely understood
  • Hyperthyroidism
    • Hypertension has been documented in 10%-23% of cats with hyperthyroidism at the time of diagnosis
    • Not uncommon for hyperthyroid cats to have concurrent CKD
    • Approximately 25% of hyperthyroid cats normotensive at diagnosis become hypertensive after treatment of their condition
    • Pathophysiology of hyperthyroid induced hypertension is poorly understood
    • Hyperthyroid cats should have their BP closely monitored before, during, and after treatment
  • Diabetes Mellitus (DM)
    • Severe hypertension in cats with DM is uncommon:
      • Prevalence rate of 0%-15%
      • Often confounded by concurrent conditions, such as CKD
      • Important to look for comorbidities in cats with DM if hypertension is identified
  • Primary Hyperaldosteronism (PHA)
    • Uncommon condition in cats
    • PHA is an excess production of aldosterone independent of its regulator, angiotensin II
    • Typically due to an adrenal tumor
    • Hypertension is present in 50%-100% of cats with PHA
    • PHA may be underdiagnosed, mistaken for CKD
    • Low serum potassium levels, weakness, polyuria (PU)/polydipsia (PD), and hypertension unresponsive to therapy should prompt further investigation
    • Clinical findings serving as clues: low potassium levels, PU/PD, ocular changes
    • Blood pressure, potassium levels difficult to regulate with conventional therapy
  • Pheochromocytoma
    • Rare tumor in cats
    • Excessive circulating catecholamine levels
    • Sustained or paroxysmal bouts of hypertension
  • Hyperadrenocorticism (HAC)
    • Uncommon condition in cats
    • Prevalence of hypertension reported to be 19%
  • Medications Associated with Hypertension
    • Erythropoiesis-stimulating agents
    • Phenylpropanolamine
    • Ephedrine
    • Chronic high-dose sodium chloride
    • Albuterol intoxication

Situational Hypertension

    • BP increase that occurs during in-practice measurement in an otherwise normotensive individual
    • Caused by autonomic nervous system alterations resulting from excitement or anxiety on higher centers of the central nervous system (CNS)
    • Resolves under conditions that decrease or eliminate the physiologic stimulus
    • Can lead to an erroneous diagnosis of pathologic systemic hypertension – there is no justification to treat situational hypertension in cats
    • There are many situations that may induce situational hypertension resulting in falsely elevated BP readings, including:
      • Acute situational (iatrogenic hypertension)
        • Anxious cats more prone
        • Trip to practice
        • Pain
        • Hospitalization
          • Intravenous fluid therapy
          • Hospitalization in same ward as dogs, ward with lights on all the time
          • Handling by staff who wear heavy scents, scrubs smelling of dogs
          • Prolonged hospital stays
          • Too frequent handling, disturbing unnecessarily when resting
      • Chronic situational
        • Generally stressed cats – behavioral
        • Pain – osteoarthritis (OA), periodontal disease, systemic disease

Confirm hypertension with repeat BP measurements at a separate visit prior to starting medical therapy except in emergent situations where there is clear evidence of ocular or neurological target organ damage (TOD). Use minimal, gentle Feline-Friendly handling in a calm, quiet environment to reduce situational hypertension.

Categorization

Categorization of hypertension ideally includes:

  • Complete and thorough history including diet, medication, and supplements
  • Complete physical examination including ophthalmic exam
  • Repeatable BP levels (note type of BP device, cuff size, limb used – see BP Assessment Form)
  • Complete blood count (CBC), chemistry profile, Symmetric Dimethylarginine (SDMA), Total T4, Free T4
  • Urinalysis, urine culture, urine protein creatinine ratio (UPCR)

Additional diagnostic tests may be considered:

  • Thoracic radiographs
  • Abdominal radiographs
  • Echocardiogram
  • Electrocardiogram
  • Abdominal ultrasound
  • Potentially ACTH stimulation test, aldosterone level

  

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© American Association of Feline Practitioners, 2021