Hypertension in Cats (Felis) | Vetlexicon
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Hypertension

ISSN 2398-2950


Introduction

  • Consistent increase in arterial blood pressure above the species normal.
  • Cause: usually secondary, eg chronic renal failure, hyperthyroidism (23-87% of cases); primary (idiopathic) cases have been reported.
  • Diagnosis: probably underdiagnosed in veterinary medicine.
  • Treatment: address underlying cause, treat hypertension with amlodipine besylate.
  • Prognosis: early screening and identification important to prevent organ damage (particularly eyes, central nervous system, heart and kidney).
    Print the owner factsheet on hypertension  Hypertension to give to your client.

Presenting signs

  • Neurological signs: depression, seizures Seizures, dementia, disorientation, etc.

Acute presentation

Age predisposition

Breed/Species predisposition

  • Some breeds have (slightly) above-average normal blood pressure ranges - this is not clinical hypertension.

Special risks

Pathogenesis

Etiology

Primary (idiopathic)

  • Rare; one colony in USA: familial hypertension.
  • 13-20% of hypertensive cats have no evidence of overt azotemia Azotemia or other underlying disease and could have idiopathic hypertension. However, some do  have reduced urine concentrating ability and may have non-azotemic CKD, and a complete work-up including abdominal ultrasound and aldosterone measurements was not always performed.

Secondary

  • Renal disease Kidney: chronic kidney disease (up to 62% of hypertensive cats has increased urea or creatinine concentrations; 19.2% of cats are hypertensive at diagnosis of CKD).
  • Hyperthyroidism Hyperthyroidism, (23-87% of cases of hypertension; 22.8% of hyperthyroid cats will develop hypertension after successful antithyroid treatment).
  • Diabetes mellitus Diabetes mellitus. (NB In humans hypertension and diabetes frequently occur concurrently, but no evidence exists that this is the same in cats.)
  • Hyperadrenocorticism Hyperadrenocorticism (rare in cats, one case report describing a SBP of 300 mmHg has been published). 
  • Primary aldosteronism Feline primary hyperaldosteronism (up to 87% of cats with hyperaldosteronism are hypertensive).
  • Others, eg neurological disorders, polycythemia, syndrome of inappropriate ADH secretion.
  • Acromegaly Acromegaly.
  • Pheochromocytoma Pheochromocytomas.

Predisposing factors

General

  • Age (related to incidence of primary disease).
  • Obesity Obesity.

Specific

  • Pre-existing disease, in particular chronic kidney disease.

Pathophysiology

  • Depends on cause.
  • Often poorly understood.

Generally

  • Arterial blood pressure = cardiac output x peripheral resistance.
  • Factors affecting cardiac output and peripheral resistance:
    • Renin-angiotensin-aldosterone system.
    • Altered adrenergic activity.
    • Renal vasodepressor/vasopressor substances.
    • Sympathetic nervous system.
    • Pressure-natriuresis.
  • All are interrelated, eg in the proposed pathophysiology of hypertension in renal disease:
    • Decreased renal blood flow   →   renin/angiotensin release   →   further Na retention and vasoconstriction   →   increased renopressor substance production.
    • Anemia   →   increased cardiac output.
    • Vascular wall stiffness, eg arteriosclerosis   →   increased peripheral resistance.
  • Proposed pathophysiology of hypertension in hyperthyroidism:
    • Increased sensitivity and numbers of beta receptors in myocardium   →   increased sensitivity to catecholamines   →   increased cardiac output.
    • Thyroid hormone-specific mediators   →   increased cardiac output.
  • Sustained hypertension   →   muscular hypertrophy and necrosis of arterial walls   →   ischemia and hemorrhage   →   end organ damage especially eyes, kidneys, brain, heart.
  • Idiopathic primary hypertension has been reported - ?familial, genetic.

Timecourse

  • Usually chronic organ damage.
  • May present acutely when organ damage occurred.

Diagnosis

Presenting problems

  • Polyuria.
  • Polydipsia.
  • Blindness.
  • Dementia, disorientation.
  • Weakness, collapse.
  • Seizures Seizures.

Client history

  • History related to primary disease, eg progressive polyuria, polydipsia.
  • Sudden blindness.
  • Weakness, collapse.
  • Dementia, disorientation, neurological deficits, etc.

Clinical signs

  • Clinical signs related to primary disease, eg anemia, pallor, dehydration.
  • Bullous retinopathy (small circular donut lesions throughout fundus).
  • Retinal hemorrhage Retina: hemorrhage  Retina: hemorrhage - DSH 10 years .
  • Hyphema Hyphema, or retinal detachment Retina: detachment  Retina: detachment - external view .
  • Neurological deficits, depression, seizures.

Diagnostic investigation

Other

  • Blood pressure measurement:
  • The recommendation is to relate blood pressure to the risk of future target organ damage (TOD) following the criteria presented in this table:
    SBP (mmHg) DPB (mmHg) Risk of future TOD Blood pressure substage
    <150 <95 Minimal Normotension
    150-159 95-99 Mild Borderline hypertension
    160-179 100-119 Moderate Hypertension
    >/= 180 >/= 120 Severe Severe hypertension

    Marked 'White Coat Effect' in cats - blood pressure often elevated by stress. Blood pressure needs to be persistently elevated or evidence of TOD needs to be present in order to make a diagnosis.

Ophthalmology  

Urinalysis

Biochemistry

2-D Ultrasonography

  • Secondary left ventricular hypertrophy.

Serology

Confirmation of diagnosis

Discriminatory diagnostic features

  • History.
  • Signs.
  • Blood biochemistry.
  • Hormone assay.

Definitive diagnostic features

  • Blood pressure measurement.
    May be difficult to differentiate from stress.
  • Evidence of hypertensive retinopathy or choroidopathy on direct or indirect ophthalmoscopy.

Gross autopsy findings

  • Complete systematic examination required to look for primary and secondary lesions, including kidneys, adrenals, eyes, nervous system and cardiovascular system.
  • Small, sclerotic end-stage kidneys; although hypertension also frequently occurs in the early stages of CKD.
  • Ventricular wall and chamber enlargements best evaluated on transverse section one third proximally from apex. Compare with normal if unsure.

Histopathology findings

  • Kidneys: fibrinoid lesions, hyalisation, myoarteritis, tubular degeneration, interstitial fibrosis.
  • Cardiac and cerebral atherosclerosis/arteriosclerosis.

Differential diagnosis

Treatment

Initial symptomatic treatment

  • Direct-acting vasodilator may be required in emergency, eg acute neurological signs:
    Either Hydralazine Hydralazine (0.5 mg/kg PO).
    Or Sodium nitroprusside Nitroprusside, constant-rate infusion [CRI] (2.5-15 ug/kg/min IV using an infusion pump for CRI and continuous monitoring of blood pressure response).

Standard treatment

  • Treat hypertension based on the risk assessment of future TOD. In practice this would mean that with SBP>160 mmHg, antihypertensive treatment should be considered.
  • Independent of the underlying cause, feline hypertension is best treated with amlodipine besylate  Amlodipine
  • Therapy is stepwise and should be started on 0.625 mg/cat/day. Dose can be gradually increased (based on blood pressure measurements) to a maximum of 2.5 mg/cat/day.
  • If hypertension is uncontrolled on 2.5 mg/cat/day, additional therapy with ACE inhibitors ACE inhibitors: overview can be considered (eg benazepril Benazepril at 0.5-1 mg/kg).
  • Primary disease needs to be diagnosed and appropriately treated.
  • Renal function must be monitored carefully.

Monitoring

  • Blood pressure (goal = <160 mmHg), and signs every 1-2 weeks until stabilized. As treatment is life-long, regular blood pressure measurements are recommended (minimum every 4 months).

Subsequent management

Treatment

  • Maintenance therapy usually continued for life unless primary condition can be cured.
  • Therapy for hypertension helps to slow progression of renal failure and vice versa.

Monitoring

  • Blood pressure measurement.
  • Renal function: blood biochemistry, urinalysis, electrolytes.
  • Ophthalmoscopic retinal examination.
  • Signs.

Prevention

Control

  • Screen for hypertension, especially if renal/cardiac disease or hormonal problems.
  • Once hypertension detected, treat early to prevent organ damage.

Outcomes

Prognosis

  • Once blood pressure is appropriately controlled, hypertension has no influence on survival.
  • Prognosis depends on underlying cause and the success of treatment thereof.

Expected response to treatment

  • Signs.
  • Sustained reduction in blood pressure measurement.
  • Resolution/lack of progression of target organ damage.

Reasons for treatment failure

  • Too severe.
  • Late diagnosis: target organ damage severe.
  • Late decompensated primary disease, eg renal failure.
  • Inappropriate/insufficient therapy, lack of response to medication.
  • Standard reasons Standard reasons for failure in a treatment.

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Taylor S S, Sparkes A H, Briscoe K et al (2017) ISFM consensus guidelines on the diagnosis and management of hypertension in cats. J Feline Med Surg 19 (3), 288-303 PubMed.
  • Bijsmans E S, Jepson R E, Chang Y M et al (2014) Changes in systolic blood pressure over time in healthy cats and cats with chronic kidney disease. JVIM 29 (3), 855-861 PubMed.
  • Brown S, Atkins C, Bagley R et al (2007) Guidelines for the Identification, Evaluation, and Management of Systemic Hypertension in Dogs and Cats. J Vet Intern Med 21 (3), 542-558 PubMed.
  • Jepson R E, Elliott J, Brodbelt D et al (2007) Effect of control of systolic blood pressure on survival in cats with systemic hypertension. J Vet Intern Med 21 (3), 402-409 PubMed.
  • Komáromy A M, Andrew S E, Denis H M et al (2004) Hypertensive retinopathy and choroidopathy in a catVet Ophthalmol (1), 3-9 PubMed.
  • Forster-Van Hijfte M (2002) Feline hypertension: pathophysiology, clinical signs and treatment options. In Practice 24 (10), 590-594 VetMedResource.
  • Elliott J, Barber P J, Syme H M et al (2001) Feline hypertension - clinical findings and response to antihypertensive treatment in 30 cases. JSAP 42 (3), 122-129 PubMed.
  • Snyder P S, Sadel D & Jones G L (2001) Effect of amlodipine on echocardiographic variables in cats with systemic hypertension. JVIM 15 (1), 52-6 PubMed.
  • Sparkes A H, Caney S M, King M C et al (1999) Inter and intra individual variations in doppler ultrasonic indirect blood pressure measurements in healthy cats. JVIM 13 (4), 314-318 PubMed.
  • Bodey A R & Sansom J (1998) Epidemiological study of blood pressure in domestic cats. JSAP 39 (12), 567-573 PubMed.
  • Henick R A (1997) Diagnosis and Treatment of Feline Systemic Hypertension. Comp Cont Ed 19 (2), 163-179 VetMedResource.
  • Sansom J, Barnett K C, Dunn K A et al (1994) Ocular disease associated with hypertension in 16 cats. JSAP 35 (12), 604-611 VetMedResource.
  • Michell A R (1993) Hypertension in companion animals. Vet Annual 33, 11-23 VetMedResource.
  • Dukes J (1992) Hypertension - a review of the mechanisms, manifestations and management. JSAP 33 (3), 119-129 VetMedResource.

Other sources of information