Feline systemic hypertension: finding the occult forms (Proceedings)
Look for an underlying disease before diagnosing primary hypertension.
- Definition
- Controversial
- Systolic > 160, 180, 200 mmHg
- Below 160 is normal
- Above 200 is abnormal
- Primary Hypertension
- The most common form in humans
- Uncommonly occurs in cats: JVIM, 8/95, p. 79. Actually may be due to hyperaldosteronism. (See below)
- Look for an underlying disease before diagnosing primary hypertension.
- Underlying Diseases
- Increased peripheral resistance: chronic renal disease
- Increased cardiac output: hyperthyroidism
- Not hypertrophic cardiomyopathy: decreased cardiac output
- Hyperaldosteronism due to an adrenal tumor.
- Minor diseases (probably not a cause in cats)
- Anemia, Cushing's disease, pheochromocytomas
- Incidence: JAAHA, 11/94
- 65% of cats with chronic renal disease
- 23% of cats with hyperthyroidism
- Clinical signs
- Sudden onset retinal blindness
- Encephalopathy: seizures, strokes, vocalization
- Cardiac (working against increased arterial pressure): systolic murmurs, gallop rhythms
- Biting at back or flanks – hyperesthesia
- Workup for a blind cat
- Check blood pressure, if possible
- History like renal or thyroid disease: WL, PU, PD, PP
- Exam findings of: small kidneys or enlarged thyroid
- Lab findings of: elevated T4 or creatinine
- Plasma aldosterone concentration ($12.00); Available from Diagnostic Center for Population and Animal Health, Michigan State University, (517) 353-0621. Submission forms can be downloaded at www.animalhealth.msu.edu. (Fee as of 9-05.)
- Rule out: toxoplasmosis, systemic fungal disease, FeLV, FIP.
- Treatment
- Step One: Lower the blood pressure
- Nitroglycerin – for first 48 hrs. after retinal detachment to give amlodipine time to work.
- Amlodipine (Norvasc): 0.625 mg/4-5 kg cat/day; adjust dose to effect
- ACE-i: they do not lower BP well so do not use them without amlodipine
- Benazepril (benefits kidneys also): 2.5-5.0 mg/cat q24h.
- Treat for 48 hours then recheck the BP
- Continue to recheck q48h until the BP is below 150 mmHg.
- If the BP is not < 150 on the third visit (2nd recheck), add benazepril.
- If the cat has renal disease, you need it anyway.
- Step Two: Diagnose and treat the underlying disease
- See above: Workup for a blind cat
- Hyperthyroidism: When controlled, BP normalizes and further treatment is not needed.
- Renal Disease: Must be treated long-term due to interaction of HT and renal disease.
- Step Three: Diet
- JVIM: May/June 2007 ACVIM Consensus Statement
- “Although frequently recommended as an initial step in the pharmacological management of high BP, dietary salt restriction is controversial, and the available evidence suggests that substantial sodium restriction alone generally does not reduce BP. In fact, sodium restriction activates the renin-angiotensin-aldosterone axis and may actually increase BP in certain settings. Currently, … the panel recommends avoiding high dietary sodium chloride intake in hypertensive animals but does not recommend that a specific effort be made solely to restrict dietary sodium chloride intake. Until more data is available, the selection of appropriate diet should be based on other patient-specific factors, such as underlying or concurrent diseases and palatability.”
- Alternative blood pressure monitors
- Syringe & needle: easiest blood sample you ever took from the cephalic vein.
- Stethoscope: hyperthyroid cats often have pounding heartbeats
- Lead II ECG: hyperthyroid cats have tall waves (or deep S waves) and tachycardia.
- Palpate for bounding pulse.
- Another sign of hypertension
- Aortic undulation
- Most dramatically seen on a lateral view of the chest.
- More often seen on a VD or DV as the aortic knob.
- Measuring blood pressure
- Avoid the “white coat effect” JVIM, 3/99, p. 134-142.
- Quite room
- No odor, sounds, or sight of dogs
- Owner present
- Get the cat comfortable
- Clinically feasible BP units are indirect since intra-arterial catheters are not practical.
- Doppler: Vet-Dopp by Vmed/DVM Solutions: 1-866-373-9627
- Oscillometric: Cardell and petMAP
- High Definition Oscillometric: Vmed/DVM Solutions: 1-866-373-9627
- The unit I am currently using.
- It allows you to evaluate the reliability of each measurement as it is being recorded.
- Number of measurements
- Do not do too often due to arterial fatigue.
- I take two reliable (see above) readings and average them.
- Measure blood pressure in the following situations
- Geriatric profiles
- Surgical monitor (Doppler)
- Suspected saddle thrombus
- Concern about proper circulation to leg or tail due to trauma
- Chronic renal disease
- Hyperthyroidism
- Murmur or gallop rhythm
- Hyphema
- Sudden onset blindness if retinal hemorrhage or detachment is present
- Anisocoria
- Epistaxis
- Stroke-like signs
- Seizures
- Hyperesthesia of back or rear legs
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