The Murmur Newsletter - February 2019

BLOOD PRESSURE MEASUREMENT METHODOLOGY

The procedure must be standardized in each hospital.¹ 

• • The same individual(s) should be responsible for all blood pressure (BP) measurements in the hospital. Training and experience are paramount.

  • CVCA solely recommends the use of Doppler blood pressure measurement equipment.  We feel this older technology represents the closest approximation to the gold standard of blood pressure measurement, direct arterial monitoring.  Oscillometric methodologies (although fancy with digital readouts) have been shown to be less reliable/accurate especially in cats and small breed dogs.

  • The environment should be isolated, quiet, and away from other animals.  Generally, the owner should be present. The patient should not be sedated and should be allowed to acclimate to the environment for 5-10 minutes prior to the BP being taken

  • The animal should be gently restrained in a comfortable position, ideally in ventral or lateral recumbency to limit the vertical distance from the heart base to the cuff.

  • The cuff width should be approximately 30-40% of the circumference of the cuff site, e.g. limb or tail depending on animal conformation, tolerance and/or user preference.

  • Only take measurements when the patient is calm and motionless.

  • The first measurement should be discarded and then an average of 5-7 measurements should be recorded.  Please note that some patients have BP readings that trend downward. In this case, once the measurements have plateaued, then take your 5-7 measurements and obtain a meaningful measurement.

  • If in doubt, e.g. very unlikely for a 2-year-old healthy cat to be hypertensive, repeat measurements with different cuff size or alternate limb/tail.

  • Record cuff size and site, patient’s demeanor, the rationale for values included/excluded, etc.

TYPES OF HYPERTENSION:

1. Situational hypertension—It is very common for our patients to suffer from anxiety from the car ride, waiting room, exam room, odors, pheromones, etc.  This alone can temporarily increase blood pressure into hypertensive ranges. There is no justification to treat situational hypertension.  

2. Secondary hypertension—This is the most common form of hypertension in veterinary medicine.  There are several disease states that commonly result in secondary high blood pressure in the veterinary patient.  Unfortunately, treatment of the underlying condition does not often result in normalization of blood pressure and treatment of the secondary hypertension is still necessary.

   • Canine

   • Kidney disease (acute and chronic with or without proteinuria)

   • Hyperadrenocorticism

   • Diabetes mellitus

   • Primary hyperaldosteronism

   • Pheochromocytoma

   • Feline

   • Kidney disease (chronic with or without proteinuria)

   • Hyperthyroidism

   • Primary hyperaldosteronism

   • Pheochromocytoma

   • Hyperadrenocorticism
     
     

3. Idiopathic/Essential hypertension—This is not commonly seen in veterinary medicine as most hypertension is secondary to some other underlying disease process.  However, some case reports state that from 13-20% of hypertensive cats may be classified as idiopathic and may be much more prevalent than previously thought.²

TARGET ORGAN DAMAGE: The rationale for treatment of hypertension in our dogs and cats is to prevent other organ damage or worsened systemic disease secondary to the chronic effects of hypertension.  Hypertension has been associated with worsening of proteinuria and renal disease, ocular changes/retinal detachment, neurologic issues, and secondary cardiac changes. The following chart excerpted from the ACVIM consensus guidelines provides an excellent summary of target organ damage from systemic hypertension.¹

DIAGNOSIS: The diagnosis of systemic hypertension is based on reliable blood pressure measurements on multiple occasions or repeatable hypertensive readings from multiple sites in a patient that is deemed at risk for hypertension based on the presence of an underlying etiology. If target organ damage is noted, then treatment should be initiated. However, if hypertension is suspected, but no target organ damage is noted, then medication may only be indicated after validation of two or more hypertensive readings on separate occasions.  Hypertension in both dogs and cats is based on the risk for target organ damage (TOD).¹

• Normotensive (minimal TOD risk) = systolic BP < 140mmHg

• Prehypertensive (low TOD risk) = systolic BP 140-159mmHg

• Hypertensive (moderate TOD risk) = systolic BP 160-179mmHg)

• Severely hypertensive (High TOD risk) = systolic BP > 180mmHg
  
  

TREATMENT/MANAGEMENT: Since hypertension is almost always (>80%) secondary to some other underlying metabolic abnormality, treatment for hypertension and additional diagnostics for a primary cause should be initiated simultaneously.  Depending on the patient, these diagnostics may include CBC, serum chemistry, UA, SDMA, quantitative assessment of proteinuria (urine protein: creatinine ratio (UPC)), serum T4 (cat), and cortisols (dog). Additional diagnostics may include an abdominal ultrasound and urine aldosterone and catecholamine levels.

Canine: The ACVIM consensus guidelines first recommends the use of a renin-angiotensin aldosterone system (RAAS) inhibitor like an ACE inhibitor (ACEi) or angiotensin receptor blocker (ARB).  The rationale to first use a RAAS inhibitor is most dogs with hypertension have some degree of renal disease and proteinuria. Calcium channel blockers (Amlodipine) preferentially dilate the renal afferent arteriole which could lead to further glomerular damage in the renally compromised patient.  However, the use of both a RAAS inhibitor that dilates the renal efferent arteriole combined with amlodipine that dilates the afferent arteriole should have a limited effect on glomerular function.¹

CVCA’s treatment approach in the canine is usually as follows:

• Idiopathic hypertension (confident no other metabolic issues/renal disease)—Amlodipine 0.1-0.5 mg/kg q 12-24 hours

• Secondary renal hypertension/proteinuria—ACEi (Enalapril, Benazepril) 0.5 mg/kg q 12 hours usually combined with amlodipine 0.1-0.5 mg/kg q 12-24 hours. Some internists will use higher dosages of ACEi or an ARB to decrease proteinuria.  CVCA’s experience with monotherapy ACEi is that an ACEi usually does not adequately control hypertension and amlodipine is required as a secondary agent.

Feline: Despite renal disease often being implicated as a primary cause of hypertension in the cat, amlodipine is always the first line of therapy for hypertension.  A mean decrease in systolic BP of 28-55 mmHg in cats treated with amlodipine is often observed.^{3, 4, 5}

CVCA’s treatment approach in the feline is usually as follows:

• Recheck blood pressure in 1-2 weeks with goal of systolic BP < 160 mmHg

• Recheck renal values and electrolytes in 1-2 weeks after starting therapy in particular if using ACEi or ARB therapy or if renal disease is preexisting.  If proteinuria was diagnosed, a repeat UPC will be indicated as well.

• Adjust dosages of primary blood pressure agent or add in secondary medication if BP cannot be decreased to < 160mmHg

• Recheck blood pressure in 1-2 weeks with goal of systolic BP < 160 mmHg

• Recheck renal values and electrolytes in 1-2 weeks after starting therapy in particular if using ACEi or ARB therapy or if renal disease is preexisting.  If proteinuria was diagnosed, a repeat UPC will be indicated as well.

• Adjust dosages of primary blood pressure agent or add in secondary medication if BP cannot be decreased to < 160mmHg

Update on the new FDA approved drug for treatment of hypertension in the cat Semintra™/telmisartan)

Semintra/telmisartan 10 mg/ml oral solution was launched by Boehringer Ingelheim this past fall. It is the only FDA approved medication to treat hypertension the feline.  It has been licensed in Europe and Canada for the past several years. The initial dosage of Semintra is 1.5 mg/kg q 12 hours for 14 days followed by 2 mg/kg q 24 hours thereafter.  If hypotension occurs at this dosage, it can be decreased by increments of 0.5 mg/kg.

The following adverse reaction tables from both the 28-day field effectiveness study and the 5-month field effectiveness and safety study: (information excerpted from Semintra package insert)

As one can see from the above adverse reactions, vomiting and non-regenerative anemia were common side effects of Semintra.  However, upon closer examination of the study population and the study itself, these cats were a median age of 14 years and all had IRIS stage 3 or greater chronic renal failure.  Thus, many of these “adverse effects” might be expected in this study population. There was also no control group in the 5-month study.

Semintra™/telmisartan is classified as an angiotensin receptor blocker with effects on the efferent renal arteriole.  Thus, monitoring of renal panels after initiation of Semintra™ is recommended just like the use of an ACEi. With the possible concern over non-regenerative anemia, it is also CVCA’s recommendation to recheck a CBC at the same time.

CVCA’s current recommendation for the use of Semintra™/telmisartan in the cat is as follows:

• CVCA still recommends amlodipine as a first line agent in the treatment of systemic hypertension (0.625 – 1.25 mg per cat q 24 hours)

• In cats with proteinuria and hypertension, Semintra™ is recommended as the first line therapeutic (1.5 mg/kg q 12 hours for 14 days followed by 2 mg/kg q 24 hours thereafter).

• In cats with inadequately controlled hypertension on a maximum dosage of Amlodipine (1.25 mg q 12-24 hours), the addition of Semintra™ is recommended as a secondary agent (same dosage as above).

SUMMARY: Hypertension can be both a frustrating condition to diagnose and treat in the dog and cat with it often being associated as a secondary disease process.  However, the therapeutics currently available to us have great efficacy and we are often quite successful in treating hypertension to either prevent and/or reverse target organ damage.  

The cardiologists and cardiology residents at CVCA are happy to assist in any manner with your patients.  Please don’t hesitate to phone/email us to discuss or refer a challenging case. Together we can achieve the best outcomes for our patients and clients.  

See last page for Works Cited Sections for “Update on Hypertension Treatment in the Dog and Cat”