Hypertension and pulmonary hypertension

• How to diagnose Systemic hypertension?

  Extremely dependant circumstances

  Fear or excitement.

  Typically requires more than just one abnormal reading

  Drugs (fluid therapy, steroids, cyclosporin A, phenylpropanolamine).

  No cut off value, only guidlines:

  Systolic > 160mmHg warrants further investigation

  Diastolic > 100mmHg warrants further investigation

  Age dependant (possible 1-3mmHg per year after 8 years old)

  Breed dependant (site hounds have a higher BP)
• What is usually meant by hypertension?

  Persistently elevated systemic blood pressure. Systemic hypertension.
• How is blood pressure determined?

  BP = CO x PVR (peripheral vascular resistance)

  The body regulates blood pressure by altering cardiac output and peripheral vascular resistance. Cardiac disease never causes hypertension.
• Initiating causes of systemic hypertension

  • Chronic fluid accumulation
  • Persistently increased heart rate
  • Chronic vasoconstriction
• Perpetuating causing of systemic hypertension

  • Small arteries changes:
  • Extravasation of plasma into the vessel wall (hyaline arteriosclerosis - physical changes ti the arterial wall).
  • Vascualr smooth muscle hypertrophy
  • Renal disease
• Renal disease and hypertension

  BP can not remain persistently elevated without abnormal sodium handling (chronic renal failure/ insufficiency).

  Kidney disease of any type result in areas of ischaemia that lead to activation of the RAAS.

  Kidney disease leads to dilation of the afferent arteriole and constriction of the efferent arteriole resulting in dramatic raises in glomerular pressures which leads to renal damage and proteinuria.
• Different causes of systemic hypertension

  Artefact

  • Stress induced
  • White-coat hypertension.

  Primary (idiopathic)

  • No underlying disease detected
  • Rare in veterinary

  Secondary

  • Underlying disease detected (most common)
• Aetiology of secondary hypertension causes

  Renal disease

  • 30-40% of dogs with CRF have hypertension,
  • Disturbance in neuroendocrine factoRAS and body fluid balance.

  Hyperadrenocorticism (dog)

  • Increases renal retention of salt and water
  • Overproduction of renin leads to vasoconstriction.

  Diabetes mellitus (dog and cat)

  • Volume expansion due to hyperglycaemia
  • Overproduction of renin: vasoconstriction.

  Phaechromocytome (rare)

  Hyperaldosteronism (rare)

  Drug therapy

  Steroids, NSAIDs, Cyclosporin A, phenylpropanolamine

  Diet

  Not as significant as in humans.
• Clinical signs of systemic hypertension

  None at the initial phase.

  Amount of proteinuria relates directly to the blood pressure. Reduction of proteinuria is the most reliable evidence of benefit in a treated animal.

  Only present with end organ damage:

  1. Ocular (hypertensive retinopathy)

  • Acute blindness, retinal detachment
  • Intraocular haemorrhage

  1. CNS (hypertensive encephalopathy)

  • Disorientation, ataxia, stupor
  • Seizure, strokes

  1. Renal (proteinuria - caused by damage to the glomerular)

  • Polyuria/ polydipsia

  1. Cardiac (left ventricular hypertrophy)

  • Murmur, arrhythmias
  • Congestive heart failure.
• Types of measuring systemic hypertension

  Direct

  • Invasive (requires arterial catheter)
  • Intra operatively
  • ICY

  Indirect

  • Non-invasive (compressive cuff)
  • Commonly used on clinics
• Indirect measurement of systemic hypertension

  Doppler:

  • Manual:
  • Requires more training
  • More user variabilty
  • Noise
  • Faster
  • Only systolic blood pressure

  Oscillometric (high definition oscillometric)

  • Automatic
  • Straightforward
  • Time consuming
  • Systolic, diastolic and mean
• Ideal way to measure blood pressure

  • Quiet and comfortable area (with owner but preferably without)
  • Patient allowed to acclimate to the room and people for 5-10 minutes, before starting examination.
  • Sedation should be avoided and gentle restrain in a comfortable position.
  • Same operative each time
• Protocol for blood pressure cuff use

  The cuff width size should measure 40% of the cuff size circumference.

  Larger cuff underestimates the blood pressure

  Smaller cuff overestimated the blood pressure.

  Cuff placed on a limb (cats) or tail (dogs).

  The patient should remain calm and motionless.

  Cuff should be maintained at the same level as the heart.

  First measurement should be discarded and an average of 3-7 consecutive measurements should be obtained.
• When to treat systemic hypertension

  • Only treat specifically for hypertension when there is a risk of end stage organ damage.
  • When there is an underlying disease identified:
  • Always treat the underlying disease
  • Low to moderate risk of end organ damage (systolic >160mmHg)
  • No underlying disease identified:
  • Clinical signs
  • Low to moderate risk of end organ damage (systolic >160mmHg)
  • No clinical signs
  • Moderate to high risk of end organ damage (systolic > 180mmHg)
• Types of treatment for systemic hypertension

  Life style

  Diet (salt restriction)

  First line in humans

  Not used in veterinary

  Diuretics (volume depletion)

  Frequently used in humans

  Only in emergency setting in veterinary patients.

  B-blockers

  ACEI

  Ca channel blockers

  combination of abvoe
• Beta-blockers

  • Reduced heart rate. And contractility
  • Atenolol (B1 selective)
  • Dogs: 0.2-1mg/kg
  • Cats 6.25-12.5mg/cat SID or BID
  • Propanolol (non selective) - not to asthmatic
  • Dogs: 0.2-1.0mg/kg TID
  • Cats: 2.—5mg/cat TID
  • Treatment of choice in hyperthyroid cats
  • Poor results as a single agent in other conditions
• ACE inhibitor treatment for hypertension

  Blocking the RAAS

  Benazepril, Enalapril, Imidapril

  Dogs and cats: 0.5mg/kg SID or BID

  Better in pathologies that lead to elevated renin levels

  Renal failure, Cushing’s disease and Diabetes.

  First choice in dogs and patients with proteinuria

  Frequently insufficient as a single agent but should always be considered.
• Ca channel blockers for hypertension

  • Vasodilators
  • Inhibit calcium influx to the cell
  • Amlodipine
  • Dogs and cats: 0.1-0.25mg/kg
  • First choice in cats (proven efficacy)
  • Commonly added to ACE-I in dogs for significant results.
  • Rapid onset (emergency)
• Angiotensin II receptor blockers for hypertension

  • Temisartan
  • Reduction of Proteinuria associated with chronic kidney disease in cats
  • The recommended dose in 1mg/kg
  • Semintra is an oral solution and is well accepted by most cats.
• Goal of hypertension treatments

  • Reduce blood pressure
  • Reduce end organ damage risk
  • Decrease proteinuria
  • Alleviate clinical signs
  • Prevent further detonation of organ function
  • Depends on the underlying disease
  • Minimise hospitalisation
  • Owner compliance
• Pulmonary circulation

  Pulmonary circulation is usually a low pressure, low resistance, high capacitance system.

  Low pressure minimises right ventricular workload.

  Increases in pulmonary blood low are usually accommodated with minimal increase in pulmonary artery pressure due to:

  Highly distensible thin walls of the pulmonary vasculature.

  Recruitment of under perfused vessels

  Large pulmonary capilliaries surface area.
• Pulmonary hypertension definition

  Systolic pulmonary artery pressure PA) >35mmHg

  Diastolic PA pressure >10mmHg
• Causes of pulmonary hypertension

  1. Alveolar hypoxia with pulmonary vasoconstriction/ remodelling.
  2. Severe respiratory disease e.g. IPF, neoplasia etc
  3. Pulmonary vascular obstructive disease
  4. Pulmonary thromboembolism
  5. Heart worm disease
  6. Pulmonary overcirculation
  7. Large congenital shunts
  8. High pulmonary venous pressure
  9. Left Sided heart failure of various cases
  10. Idiopathic
• Pathophysiology of lung disease

  Increased pulmonary vascular resistance causes an increase in pulmonary arteriole pressure.

  Vasoconstriction due to hypoxia increased PVR and pulmonary hypertension can occur or worsen if present.

  Severe PH will induce angioproliferative changes that will permanently reduce vascular compliance and lumen size.

  When enough of these vessels are damaged and their ability to dilate is lost there is an increase in PVR hence an increase in PH.
• Pulmonary Vascular obstructive disease

  Stuff inside the pulmonary arteries, most common cause is heart worms.

  endothelium damage, epithelial disease, hypocoagulable state, dogs don’t normally have this state but can get it with certain states.
• Pulmonary over circulation

  If you have a large ventricular septal defect (VSD) or a atrial septal defect (ASD) and shunt a lot of blood from th elect to the right side of the heart, you increase the volume of blood going to pulmonary arteries, turning them into much more like systemic arteries than pulmonary arteries.
• High pulmonary venous pressure

  Pulmonary capillary pressure is high, right ventricle is having to inject blood into a system that is a higher pressure than normal, develop secondary can develop inot right sided heart failure if the pressure is high enough.
• Chronic pulmonary venous hypertension

  Can induce structural changes in pulmonary capillaries and increase the muscularity of resistance arterioles.

  Pulmonary oedema associated with high venous pressure attribute to increased Pulmonary vascular resistance by causing reduced lung compliance and increased resistance to airflow.

  Hypoxia induced PA vasoconstriction.
• Common clinical signs of pulmonary hypertension

  • Exercise intolerance
  • Cough
  • Respiratoray difficulty
  • Syncope
  • But remember those cases with left sided congestive heart failure.
  • Right sided murmur
  • With severe PH can have split S2.
• Diagnosing pulmonary hypertension

  • Historical and clinical findings
  • Thoracic radiographs
  • Echocardiography (only way to definitively diagnose)
  • Electrocardiography
  • Invasive cardiac catheterisation
  • CT scan
• Signs in radiographs of pulmonary hypertension

  Cardiomegaly - especially right sided enlargement

  Enlarged pulmonary arteries

  Right apical murmur > left apical murmur

  Right sided heart failure signs - hepatomegaly, large caudal vena cava, pleural effusion.

  Pulmonary parenchymal infiltrates - reflecting primary lung disease.
• Signs of pulmonary hypertension in echocardiography

  Changes are proportional to severity of pulmonary hypertension

  Right ventricle hypertrophy (>1/2 thickness of left ventricle wall) and dilation.

  Pulmonary artery dilation

  Right atrial enlargement

  Flattened intraventricular septum.
• Treatment for pulmonary hypertension

  • There is no cure
  • Few treatment options
  • Treat underlying disease
  • Sildenafil - pulmonary arterial vasodilator, but if pulmonary arteries have permanent damage will not help.
  • Pimobendan
  • Oxygen therapy
  • Enothelin antagonists - Bosentan