Vascular diseases in dogs and cats Flashcards
Name two indirect methods of measuring blood pressure
Doppler
Oscillometric
Define systemic hypertension
Sustained increased of systemic blood pressure
List the main causes of systemic hypertension
Environmental or situational
Secondary to other diseases
Idiopathic hypertension
List 3 major indicators for blood pressure recording?
Assessing severity of heart disease
Identification of systemic hypertension
Assessing response to drugs
List some causes of secondary systemic hypertension
- Chronic renal failure
- Hyperthyroidism (cats)
- Hyperadrenocorticism
- Diabetes
- Liver disease
- Hypothyroidism
- Acromegaly
- Hyperaldosteronism
- Chronic anaemia (cats)
- Obesity
- CNS disease
Which 4 systems in the body are most affected by hypertension?
Ocular
CNS
Cardiac
Renal
How does hypertension impact the cardiovascular system?
- Concentric LV hypertrophy
- Development of heart murmurs
- Degenerative valve disease
How is systemic hypertension classified in dogs and cats?
Based on the risk of target organ damage
Name 2 ocular manifestations of systemic hypertension
Hyphaema (bleed inside the eye)
Retinal detachment
Describe the blood pressure levels in:
1. Normotensive animal - minimal TOD risk
2. Prehypertensive animal - low TOD risk
3. Hypertensive animal - Moderate TOD risk
4. Severly hypertensive animal - high TOD risk
- <140mmHg
- 140-159mmHg
- 160-179mmHg
- > 180mmHg
How is systemic hypertension treated?
- The underlying cause must be identified and treated (e.g. hyperthyroidism)
- Amlodipine is the drug of choice to reduce systemic blood pressure
How does Amlodipine work to reduced systemic hypertension?
Ca channel antagonist
If there is a significant proteinuria with systemic hypertension, which drug is indicated for treatment?
Benazepril (or other ACE inhibitors)
Describe the action of ACE inhibitors
Reduce glomerular capillary pressure and reduce protein loss and therefore progression of renal disease in cats
Have a different effect on afferent and efferent arterioles
ACE inhibitors can be paired with which other drugs to reduce blood pressure?
Angiotensin II receptor blockers
Blood clots may form within the heart or circulation with changes to any one or more of the following (known together as Virchow’s triad):
- Stasis of blood flow
- Hyper-coagulable state
- Damaged endothelium
Describe the pathophysiology arterial thrombosis/emboli in cats
- A thrombus normally forms in the left atrium, due to myocardial disease associated with marked left atrial dilation - stasis of blood flow, plus a possibly damaged endocardium
- Cats’ platelets are highly reactive, and embolization results in further platelet activation, with further platelet aggregation and adhesion
- Vasoconstriction of collateral vessels
Where does embolisation most commonly occur in cats?
In the distal aorta - Feline arterial thromboembolism (FATE)
Saddle embolus
How do cats with FATE present?
Severe, acute pain and loss of function e.g. both hindlimbs
Affected limbs are cold, nail beds and non-pigmented pads may be cyanotic
Muscles are painful on palpation and in spasm (ischaemic neuromyopathy)
What is the prognosis of FATE in cats?
Grave
How does a thromboembolism appear on echocardiography?
‘Smoke’ in the left atrium
Describe the two drugs used to help prevent FATE in cats
- Clopidogrel (Plavix®) is an antiplatelet drug, inhibiting the binding of ADP to its platelet receptor.
- Aspirin helps prevent further platelet activation
Which drugs can be used in cats with FATE to reduce activation of the coagulation cascade?
Unfractionated heparin
Describe the pathophysiology of thrombus formation in dogs
- Rare in cardiac disease
- Occurs as a consequence of an endocrinopathy e.g. Cushing’s disease, Hypothyroidism.
- Also commonly affects distal aorta, possibly only single limb
How do dogs with an arterial thromboembolism present?
Hindlimb weakness or pain, worse with exercise
Pale / Pulseless / Cold compared with non-affected limb
How are dogs with an arterial thromboembolism treated?
Address the underlying condition
Analgesia
List some causes of pulmonary hypertension
- Pulmonary vascular changes e.g. Dirofilaria or Angiostrongylus infections
- High left atrial pressure due to left sided congestive heart failure
- Pulmonary thromboembolism
- Respiratory conditions e.g. brachycephalic obstruction
How can pulmonary hypertension be diagnosed by auscultating the heart?
Loud second heart sound (S2) - may be split due to delayed pulmonic valve closure
Murmur of tricuspid regurgitation may be present or loud
How can pulmonary hypertension be diagnosed on radiography?
Right heart enlargement, and pulmonary arterial dilation
How might a dog with pulmonary hypertension present?
- Syncope
- Respiratory distress/increased respiratory effort
- Exercise intolerance
- Right sided HF
- Cyanotic or pale mm
How might a dog with pulmonary hypertension present on echocardiography?
- High tricuspid regurgitation velocity
- Decreased size of LV
- Right ventricular hypertrophy: wall thickening, chamber dilation
- Pulmonary artery enlargement
- Right atrial enlargement
- Caudal vena cava enlargement
What are the aims of treating pulmonary hypertension?
- Decrease the risk of progression or complications
- Target underlying diseases or factors contributing to PH
- PH-specific treatment
List 4 drugs that can be used to treat pulmonary hypertension
Vasodilators:
- Sildenafil
- Pimobendan
- Tyrosine kinase inhibitors
- L-arginine
How is pulmonary thromboembolism diagnosed?
- Results in large ventilation: perfusion mismatch: this can be diagnosed on arterial blood gas analysis by identifying a large Alveolar (A) to arterial (a) oxygen gradient.
- FDPs (fibrin degradation products) or D-dimers (more specific in the dog and cat) indicate clot breakdown, and elevated levels suggest PTE
Name the heartworm spp of dogs
Dirofilaria immitis
Describe the life cycle of Dirofilaria immitis
- Intermediate host is the mosquito: needs warm temperatures to allow L1 to mature into infective stage in the mosquito
- L3 transmitted with mosquito bite into dog.
- L3 -> L5 in pulmonary arteries
- Microfilaria released into blood stream (so can infect another mosquito).
How long is the PPP of dirofilaria?
6 months
What is Caval syndrome?
The result of right sided congestive heart failure as a consequence of a severe worm burden.
How is Dirofilaria immitis diagnosed?
- Thoracic radiographs / echocardiography
- Heart worm antigen tests.
- Blood microfilaria test (only dogs with patent infection, over 6 months of likely infection)
- Antibody test (cats)
Describe the migration of dirofilaria in the body
Parasites live in the distal parts of the pulmonary vessel. As they grow they migrate further to the heart -> pulmonary artery -> right ventricle -> right atrium -> vena cava (occlusion)
Describe diagnosis of Dirofilaria in cats
- Antigen test and echocardiography: +ve test diagnostic, -ve test may be inconclusive
- Antibody test and radiography: +ve test increases suspicion, -ve test decreases suspicion
Which treatment of heartworm is indicated with very heavy worm burdens?
Mechanical removal (by jugular catheterisation and retrieval forceps).
Which drugs are used to treat heartworm?
- Adulticide + strict rest
- 3-4weeks later -> Microfilaricide (ivermectin)
- Concurrent doxycycline
Name the ‘french heart worm’
Angiostrongylus vasorum
Where is Angiostrongylus vasorum found in the body?
Pulmonary vessels
What are the clinical signs of an Angiostrongylus vasorum infection?
Cough
Shortness of breath
Hypoxaemia
Exercise intolerance
Coagulopathies
CNS signs
How is Angiostrongylus vasorum diagnosed?
Need index of suspicion – may be weird clinical signs!
Faecal Baermanns to see larvae
Rectal swab, smeared onto slide, direct microscopy
Angio Detect (IDEXX) - snap tes t
Describe the typical appearance of L1 Angiostrongylus vasorum
~0.4 mm long and 15 micrometers thick.
Their tail is typically curved, with a dorsal spine.
How is Angiostrongylus vasorum treated?
- Fenbendazole
- Moxidectin
- Milbemycin oxime
