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Hypertension
Description:
- Hypertension is defined as the pathological elevation of arterial blood pressure.
- There are two main types of hypertension, systemic hypertension (affects the systemic circulation) and pulmonary hypertension (affects the pulmonary circulation).
- Blood pressure in veterinary patients is not measured routinely; therefore hypertension is usually only diagnosed after clinical signs become apparent.
Systemic Hypertension
- Primary systemic hypertension= idiopathic increase in arterial blood pressure
- Secondary systemic hypertension=increase in arterial blood pressure secondary to a pathological process
- The ocular system, cardiovascular system, and nervous system are the most vulnerable to elevated arterial blood pressures. However, some endocrine disturbances have also been found to predispose animals to hypertension.
Signalment
Dogs: male>female; obese animals; middle to old age
Cats: middle to old age
Diagnosis
History & Clinical Signs
- Signs are the result of ischemia, edema, and/or haemorrhage of the affected areas
Neurological Signs
-Depression
-Seizures
-Syncope
-Paresis
-Vestibular Signs
-Ataxia
Cardiac Signs
-Left Ventricular Hypertrophy
-Heart Failure
-Systolic Murmur
-Gallop rhythm
Ocular Signs
- In cats, ocular abnormalities from hypertension are usually the first thing detected.
-Blindness
Fundic Examination
-Hyphemia (Blood in the anterior chamber)
-Retinal Haemorrhage
-Retinal Detachment
-Retinal Degeneration
Renal Signs
- Renal disease can both be caused by hypertension and cause hypertension.
- Chronic renal failure is the most common cause of hypertension showing clinical signs in dogs and cats.
-Renal Disease (especially glomerular damage)
- Glomerular damage allows protein leakage, therefore animals with hypertension are more proteinuric than unaffected animals
Endocrine Signs
-Hyperthyroidism (cats)
-Hyperadrenocorticism, Diabetes Mellitus (dogs)
Physical Exam
Blood Pressure Measurement
- Systolic Pressure> 175 indicates hypertension in a relaxed dog or cat
- Diastolic Pressure> 100 indicates hypertension in a relaxed dog or cat
1. Direct Blood Pressure Measurement (Invasive)
- Uses an indwelling arterial catheter
-Measures systolic, diastolic, and mean arterial pressures
-Used on very ill patients or those undergoing anaesthesia
2. Indirect Blood Pressure Measurement (Non-invasive)
- Two types that measure systolic arterial pressure
-Doppler Flow Technique: good for large dogs, poor for cats
-Oscillometric Technique: good for small dogs, good for cats
Treatment
Cats
- Treat the underlying problems
- Calcium Channel Blocker (e.g. amlodipine)
- Monitor Blood Pressure
Dogs
- Treat the underlying problems
- Monitor Blood Pressure
Dogs with Renal Disease:
- ACE-inhibitor (e.g. enalopril): Given alone or in combination with some of the other treatments listed below.
- Calcium Channel Blocker (e.g. amlodipine)
- Sodium Restricted Diet
- Beta Blockers (e.g. atenolol)
- Diuretics (e.g furosemide)
- Vasodilators (e.g. enalopril)
Prognosis
-Cats with hypertension are more successfully treated than dogs.
Pulmonary Hypertension
Description:
- Pulmonary hypertension=increase in pulmonary arterial pressure
There are two types of pulmonary hypertension:
1. Primary pulmonary hypertension=idiopathic pulmonary hypertension (Contributing factors: Drugs, Toxins, Genetic Predisposition and Infections)
2. Secondary pulmonary hypertension=pulmonary hypertension resulting from an identifiable underlying condition
- cor pulmonale=right sided heart failure resulting from pulmonary hypertension
- Pulmonary thromboembolism from neoplasia, heart worm disease, and other factors can cause cor pulmonale by blocking the pulmonary vessels with emboli leading to increased pulmonary arterial pressures and ultimately right sided heart failure.
- The hypoxic conditions at high elevations or animals with chronic airway disease contribute to pulmonary hypertension through hypoxia-induced vasoconstriction.
Signalment
- Some diseases predispose animals to secondary pulmonary hypertension.
Genetics & Breed Predisposition: Brachycephalic Dogs (chronic obstructive pulmonary disease); Small breeds (mitral endocardiosis); West Highland White Terriers (Pulmonary Fibrosis)
Diagnosis
History & Clinical Signs
- Signs of right sided heart failure:
-Exercise Intolerance
-Dyspnoea
-Coughing
-Syncope
-Cyanosis
-Abdominal Distension
-Distended Jugular Veins
Physical Exam
- Depends on underlying conditions
-Heart Murmur (Mitral or tricuspid regurgitation)
-Gallop Rhythm
-Increased Lung Sounds
-Splitting of S2 heart sounds
Laboratory Findings
-Arterial Blood Gases (Hypoxemia): If there are low oxygen conditions
-Complete Blood Count (Eosinophilia): If parasitic involvement; Serology or Fecal Baermann tests confirm parasitic involvement
-Biochemistry (Hyperglobulinemia): If Chronic Inflammation
-Urinalysis (Proteinuria): If Systemic Disease
Radiography
DV view
-Left atrial and ventricular enlargement
-Pulmonary arterial enlargement
-Congested pulmonary veins
-Signs of pulmonary disease
Electrocardiography
-Right ventricular hypertrophy (Deep S-waves)
-Signs of myocardial hypoxia (ST segment abnormalities)
Echocardiography
-Calculation of pulmonary arterial pressures
-Enlargement of right-side of heart
-Visualize mitral or tricuspid regurgitation
Treatment
Treat the underlying conditions:
- Treat right sided heart failure
- Treat pulmonary thromboembolism with heparin and then warfarin
- Treat chronic obstructive pulmonary disease
Prognosis
-Depends on the disease condition and ability to control it
-Poor when pulmonary damage is irreversible
Thrombosis
Description
Thrombosis is a localized or generalized intravascular clot formation. Thrombi form as the result of trauma or pathological processes affecting the blood vessel endothelium or disturbances to blood flow and/or blood composition. Some diseases such as infective endocarditis and heart worm increase the risk of thrombi formation.
Diagnosis
History & Clinical Signs
- Signs depend on the area affected and the size of the blocked vessel.
- Poor perfusion below affected area.
- Malfunction and necrosis of affected organs
Laboratory Findings
Abnormalities associated with lack of blood perfusion and/or pathological conditions.
Ultrasonography
- Blood stasis
- Visualization of a thrombus
Angiography
- May show lack of opacity in affected region
Treatment
-Treat underlying problem
-IV Fluids
-Anticoagulant (Heparin for short term treatment, Aspirin for long term treatment)
Prognosis
-Depends on underlying condition
Thromboembolism
Description
- As the name implies, a thromboembolism is a clot (thrombus) or foreign body that blocks vessels a distance away from its original site of origin.
- The most significant sites of thromboembolic formation are the following: lungs, CNS, terminal aorta, kidneys.
Requirements for thromboembolism formation:
1. Disruption of endothelial integrity
2. Disruption of flow
3. Disruption of blood haemostasis
4. Disruption of fibrinolysis
The incidence of thromboembolism greatly increases with certain diseases including:
-Heart Disease
-Neoplasia
-Blood Disorders
-Parasitic Diseases
-Hyperadrenocorticism
Diagnosis
History & Clinical Signs
5 P's:
-Pain
-Paresis
-Pallor
-Pulselessness
-Polar (cold extremities)
Long Term Effects:
-Necrosis
Specific Problems:
- Signs are dependant on site of thromboembolism
-Neurological problems (acute)
-Renal Failure (acute)
-Dyspnoea (acute)
Laboratory Findings
- Heavily dependent on thromboembolic site
-Hyperkalemia
-Acidosis
-Increased Lactate
-Azotemia
-Elevated serum creatine phospohokinase
Radiography, Echocardiography, Angiography
-Clots may be seen by the above methods
Treatment
-Treat underlying conditions
-Pain Relief (e.g. morphine)
-Support with IV fluids
-Anticoagulants:
1. Heparin
2. Aspirin
Prognosis
-Grave
Arteriovenous Fistula
Description
- As the name implies, an arteriovenous fistula is an abnormal direct connection between an artery and a vein. This connection causes the capillary circulation to be completely ignored. We will concentrate on peripheral fistulas here.
The consequences of an arteriovenous fistula are the following:
1. Increased blood return to the right heart raises cardiac output
2. Decreased blood perfusion at the affected site
3. Venous hypertension
- Predisposing causes of arteriovenous fistula formations are: trauma, surgery, neoplasia, etc.
Diagnosis
History & Clinical Signs
- Signs depend on where the AV fistula has formed.
-Subcutaneous edema
-Warm Swelling
-Inflammation
-Pain +/-
-Palpable vibration (thrill) over fistula
-Increased pulse & heart rate
-Audible continuous murmur over the fistula site
-Branham sign (decreased heart rate with surgical occlusion of blood flow to fistula)
Angiography
-Abnormal direct connection between an artery and a vein
Ultrasonography
-Abnormal flow visualized
Treatment
-Surgical ligation of abnormal vessels to and from the fistula area
-(+/-) Amputation
Prognosis
-Good with complete ligation and cessation of blood flow through the fistula
-Poor if surgical ligation is unsuccessful at stopping blood flow through the fistula
Vasculitis
Description
- Vasculitis is an inflammatory disease of the vessels.
- Causes of vessel inflammation are due to the following: neoplasia, infection, toxins, drug reactions, trauma, drug reactions, hypersensativity reactions etc.
Diagnosis
History & Clinical Signs
-Heat
-Edema
-Pain
-Petechiation
-Thrombosis
-Hemolysis