The short answer
Systemic hypertension is a sustained rise in systolic blood pressure (SBP). In dogs and cats it is usually secondary to another disease, most often chronic kidney disease (CKD), and less often has no identifiable cause. The 2018 ACVIM consensus statement diagnoses it from repeated, standardized indirect measurements and sorts patients into four SBP categories according to their risk of target organ damage (TOD), meaning injury to the eyes, brain, heart, and kidneys. Treatment guidance differs by species: the ACVIM panel favors renin-angiotensin-aldosterone system (RAAS) inhibitors as first-line drugs in dogs, and both the ACVIM and ISFM guidelines name amlodipine as the first choice in cats.
Key takeaways
- The ACVIM panel classifies dogs and cats as normotensive below 140 mm Hg SBP and severely hypertensive at 180 mm Hg or higher [1].
- The ISFM guidelines use International Renal Interest Society (IRIS) cut-offs instead, in which normotensive means SBP below 150 mm Hg [2].
- The ACVIM panel does not recommend routine screening of all dogs and cats but considers annual screening reasonable from 9 years of age [1].
- In most cases, the ACVIM statement advises confirmation over more than two sessions unless TOD is already present. It also notes that anxiety in the clinic can raise readings [1].
- In the 221-cat per-protocol population of a randomized trial, telmisartan lowered SBP by a least squares mean of 23.3 mm Hg at day 14, compared with 7.5 mm Hg on placebo [4].
- The ACVIM statement notes that amlodipine control has not been shown to extend survival in hypertensive cats [1].
Doses on this pageEvery dose below is quoted from the cited source. Verify against the current label/formulary and the patient's full clinical picture.
Definition and who is affected
The ACVIM statement describes three types of high blood pressure:
- Situational hypertension comes from the measurement process itself in an animal that is otherwise normotensive.
- Secondary hypertension accompanies a disease, drug, or toxin known to raise pressure.
- Idiopathic hypertension occurs without overt disease that could explain it [1].
The panel prefers "idiopathic" to "essential" because subclinical kidney disease is common in hypertensive animals [1]. It estimates that 13% to 20% of hypertensive cats have the idiopathic form [1][2]. The Merck Veterinary Manual takes a different view and calls essential hypertension "extremely rare in dogs and cats" [3].
The ACVIM statement links several conditions to secondary hypertension: CKD, acute kidney disease, hyperadrenocorticism, diabetes mellitus, primary hyperaldosteronism, and pheochromocytoma, with hyperthyroidism added for cats [1]. According to the ISFM, between 19% and 65% of cats with CKD have been found to be hypertensive. Nearly 25% of hyperthyroid cats that are normotensive at diagnosis may become hypertensive once the thyroid disease is controlled [2]. Drugs the ACVIM statement associates with raised pressure include erythropoiesis-stimulating agents, phenylpropanolamine, and toceranib [1]. The ISFM reports a median age at diagnosis in cats of 13 to 15 years [2].
Presentation and target organ damage
The ACVIM panel writes that hypertension matters "only because chronically sustained increases in BP cause injury to tissues" [1]. Retinopathy and choroidopathy are common in both species. The panel identifies exudative retinal detachment as the most frequent finding, and acute blindness can be the reason for the visit [1]. It reports ocular injury at SBP as low as 168 mm Hg, with risk rising sharply above 180 mm Hg [1]. Vision generally returns in only a minority of patients, even though treatment can lead to retinal reattachment [1].
The guidelines describe several other forms of TOD:
- Encephalopathy with seizures, disorientation, or vestibular signs. Neurological signs were reported in 15% to 46% of hypertensive cats [2].
- Left ventricular hypertrophy with gallop sounds or murmurs [1][2].
- Kidney effects, including progression of kidney disease and proteinuria [1][2].
Many affected animals show no obvious signs, and the ISFM notes that hypertension is "probably" underdiagnosed in cats [2][3].
Measurement and diagnosis
The ACVIM panel reports that no indirect device has yet met validation standards in conscious dogs or cats, and advises caution with the devices currently available [1]. Its protocol includes:
- a quiet room away from other animals;
- 5 to 10 minutes of acclimation;
- a cuff width of 30% to 40% of limb circumference at the cuff site;
- discarding the first reading and averaging 5 to 7 consecutive consistent readings [1].
The ISFM states that Doppler correlates well with direct measurement in cats. Traditional oscillometry tends to underestimate high pressures in cats, and high-definition oscillometry gives acceptably accurate systolic values only [2].
Situational hypertension is the main testing pitfall. The ISFM cites a radiotelemetry study in which SBP changed by up to 80 mm Hg during a simulated clinic visit [2]. The ACVIM panel states that high readings in otherwise healthy, particularly young, animals "should be assumed to represent situational hypertension until proven otherwise" [1]. It also reports that sight hounds read higher in hospital than other breeds [1].
Under the ACVIM statement, TOD justifies treatment after a single measurement session. Otherwise, in most cases, results should be confirmed on more than two occasions. That can take 4 to 8 weeks for SBP of 140 to 179 mm Hg but should take 1 to 2 weeks at 180 mm Hg or higher [1]. Once hypertension is confirmed, the panel recommends a search for underlying disease. The tests it lists include CBC, biochemistry, urinalysis, SDMA, and quantification of proteinuria [1]. The ISFM suggests BP checks at least every 6 to 12 months for healthy cats aged 11 or older, and every 3 to 6 months for cats with risk factors [2].
Classification by target organ damage risk
| SBP category (risk of TOD) | ACVIM 2018 [1] | IRIS, as cited by ISFM [2] |
|---|
| Normotensive (minimal) | below 140 mm Hg | below 150 mm Hg |
| Prehypertensive or borderline (low) | 140-159 mm Hg | 150-159 mm Hg |
| Hypertensive (moderate) | 160-179 mm Hg | 160-179 mm Hg |
| Severely hypertensive (high) | 180 mm Hg or higher | 180 mm Hg or higher |
The ACVIM panel recommends treating any patient whose BP sits persistently in the hypertensive or severely hypertensive band [1]. It describes the ideal target as SBP below 140 mm Hg, with a minimum goal of 160 mm Hg or lower [1]. The ISFM suggests an initial target below 160 mm Hg in cats and considers below 150 mm Hg a possible long-term goal [2]. Merck takes a more conservative position and recommends documenting end-organ damage before treatment begins [3].
Treatment approaches
Both guidelines advise treating any underlying disease alongside the hypertension, not before it [1][2]. The ACVIM panel describes a gradual reduction in pressure as the goal and warns against acute marked drops [1]. It recommends avoiding high dietary salt but calls salt restriction "controversial" [1].
Dogs
The ACVIM panel says RAAS inhibitors are often first-line in dogs because they reduce proteinuria and CKD is common in hypertensive dogs [1]. It suggests an ACE inhibitor such as "0.5-2.0 mg enalapril or benazepril/kg PO q12h", with telmisartan at "1.0 mg telmisartan/kg PO q24h" as an alternative [1]. For dogs above 200 mm Hg, the panel considers it appropriate to give a RAAS inhibitor together with amlodipine at "0.1-0.5 mg/kg amlodipine PO q24h" [1]. It advises against amlodipine alone in dogs because of possible glomerular injury [1]. Merck differs here, describing amlodipine and hydralazine as "the only consistently effective drugs" in dogs [3]. For dogs with concurrent CKD, the ACVIM statement sets a secondary goal of cutting the urine protein-to-creatinine ratio by 50% or more [1].
Cats
Amlodipine is the first-choice drug in both cat guidelines [1][2]. The ACVIM statement cites data indicating that a starting dose of "0.625 mg per cat per day" is effective when SBP is below 200 mm Hg. Cats above 200 mm Hg may benefit from a higher starting dose of "1.25 mg per cat per day" [1]. Per the ISFM, SBP typically falls by 30 to 70 mm Hg, and 60% to 100% of cats respond to amlodipine alone, although some need a dose adjustment [2]. The ACVIM panel does not recommend ACE inhibitors as first-line agents in cats, describing their effect on SBP as small [1].
A multicenter, double-blind, placebo-controlled trial of telmisartan enrolled cats with SBP of 160 to 200 mm Hg, and 221 cats made up the per-protocol analysis. The cats received "1.5 mg telmisartan/kg PO q12h for 14 days, followed by 2 mg telmisartan/kg PO q24h" [4]. The authors reported that the decrease persisted over 6 months [4]. They also noted that cats above 200 mm Hg or with severe TOD were excluded, so efficacy in that group remains to be further investigated [4]. The trial was funded by Boehringer Ingelheim, and four authors are company employees [4]. Merck lists amlodipine, telmisartan, or the two combined as the treatment for cats [3].
Emergencies, prognosis, and client communication
The ACVIM panel states that marked increases in BP accompanied by signs of ongoing acute TOD, such as retinal detachment or seizures, warrant immediate and aggressive treatment. It specifies that SBP of 180 mm Hg or higher with signs of intracranial TOD necessitates immediate emergency treatment. In these cases it recommends lowering SBP by about 10% in the first hour and roughly 15% more over the next few hours [1]. It names fenoldopam as possibly one of the more feasible parenteral options, and notes there are no comparative veterinary studies of these drugs [1]. The ISFM states that amlodipine monotherapy may still be effective in emergencies and should be used whenever oral administration is possible, safe, and likely to be adequate [2].
The prognostic evidence is limited. The ACVIM statement identifies proteinuria as a key predictor of survival in hypertensive cats [1]. It also notes that amlodipine control has not been shown to increase survival [1].
On client communication, the ACVIM panel stresses that hypertension is usually silent, so owners may underestimate treatment that brings "little immediate observable benefit" [1]. It recommends that clients receive BP results and an explanation of complications and treatment goals. The panel adds that "The owner should never leave the office without a clear plan for reevaluation, including a future appointment" [1].
