Vascular dx in dogs & cats

List the indications of measuring BP

• Anaesthetic monitoring

• Assessing severity of heart dx —> hypotensive = grave prog indicator

• Identification of systemic hypertension

• Assess response to drugs (vasodilators, anti-hypertensives etc.)

List the methods of measuring BP

• Direct (more likely in anaesthetised)

• Indirect

  • Doppler technique (measures systolic only)

  • Oscillometric technique (patient must be still & have no arrhythmias) —> systolic & diastolic pressure, HR

What is normal BP in dogs and cats?

Dogs —> 133/75 mmHg

• Higher in sighthounds

Cats —> 125/80 mmHg

Can get situational hypertension i.e. when stressed (keep in mind)

What values suggest systemic hypertension?

• Systolic = >160 / 175 / 180

• Diastolic = >95 - 100

has potential to cause severe organ damage

What are the main organs targeted by hypertension?

• Eye (retina)

• Brain

• Myocardium

• Kidney

Severity based on risk of 'target organ damage'

What are the main consequences of systemic hypertension?

• Ocular —> retinal haemorrhage, hyphaema, retinal detachment, blindness)

• CNS effects

• Renal failure/ proteinuria

• Cardiac —> LVH, heart murmurs due to LVOTO / MR

What should you do if you diagnose hypertension?

• Check for end-organ damage

  • examine retinas

  • hx & neuro exam

  • check SG of urine sample

  • ECG

• Search for underlying cause —> 1° hypertension v. rare

List diseases associated with 2° systemic hypertension

• CRD

• Hyperthyroidism (cats)

• Hyperadrenocorticism

• Diabetes mellitus

• Liver dx

• Hypothyroidism

• Acromegaly

• Phaeochromocytoma

• Hyperaldosteronism

• Chronic anaemia (cats)

• Obesity

• CNS dx

How is systemic hypertension treated?

• If very severe (systolic >200) should treat before other investigations

• Amlodipine —> Ca channel antagonist

• Check BP after one week (up-tire if required)

• ACEi (e.g. Benazepril) first in a dog usually then add amlodipine

• Can add Telmisartan (AngII blocker)

Recall the factors in Virchow's triad which leads to clot formation

What is feline arterial thrombo-embolism? (FATE)?

• Any condition causing stasis in heart resulting in thrombus formation

• Usually in LA —> embolisation may be to any region; often distal aorta

• Initial embolus causes further platelet aggregation & adhesion → further activation of coagulation cascade & vasocon of lateral vessels→ viscious cycle

What are the clinical signs of FATE?

• Severe

• Loss of use of HLs

• Marked pain

poor prog due to underlying heart dx

How is FATE treated?

• Priority = Analgesia & anxiolytic

  • meth, buprenophine, morphine

• Stabilise heart failure

• Could use tissue plasminogen activator as it is 'clot busting'

• Clopidogrel / aspirin / heparin to inhibit further platelet aggregation

• Euthanasia reasonable —> bad prognosis (<50% survival)

  • survival may not have full neuro recovery —> may still drag back legs

How does FATE present on echo?

'Smoke' in LA

Can see thrombus in left atrial appendage

What can you use for prevention of FATE in @ risk cats?

• Aspirin @ low dose

• Clopidogrel

  • better than aspirin @ preventing further events / improving survival

• Low molecular weight heparin (e.g. dalteparin)

• Consider oral anti-coags e.g. Rivaroxaban / Apixaban

• Treat cardiac dx

Describe the MOA of unfractionated heparin vs LMW heparin

Unfractionated

• Major effect on interaction of thrombin and antithrombin III, to initiate platelet aggregation and thrombosis.

• Heparin-ATIII also inhibits factor Xa and other factors of coagulation cascade

• Monitor APTT – increase x 1.5 - 2 fold

LMW

• Anti-Factor Xa

• Do not need to monitor coagulation times

• Can train owners to inject once or twice daily

How does arterial thrombo embolism present in dogs?

• Cavaliers predis?

• Hindlimb weakness or pain, worse w/ exercise

• Pale / pulseless / cold c.f. w/ non-affected limb

What is canine ATE more commonly associated with?

• Endocrinopathy e.g. Cushing’s dx, Hypothyroidism.

• Rarely heart dx

List the different types/ causes of pulmonary hypertension

Type 1 —> Pulmonary arterial hypertension (e.g. vascular changes with shunting defects & Eisenmengers)

Type 2 —> ass. w/ left heart failure – high LA pressure (post-capillary) e.g. caused by mitral valve dx

Type 3 —> ass. w/ respiratory disease / hypoxia e.g. brachys / idiopathic pulmonary fibrosis

Type 4 —> pulmonary thrombo-embolism

Type 5 —> parasitic e.g. Dirofilariasis, Angiostrongylosis → vascular changes

How does a PH (pulmonary hypertension) case present?

• Exercise intolerance, syncope, shortness of breath on exertion/ stress

• Loud S2, loud TR murmur

How does PH present on Rx and echo?

Rads —> dilated, tortuous or pruned pulmonary arteries

Echo:

• Dilated & hypertrophic RV

• Dilated pulmonary trunk

• High velocity TR, PR jets

What are the consequences of PH?

R-CHF → cor pulmonale (due to lung dx e.g. pulmonary fibrosis)

How is PH treated?

• Treat underlying dx

• Sildenafil (viagra) —> anti-phosphodiesterase V inhibitors

• Pimobendan? Amlodipine

What is PTE (pulmonary thrombo-embolism) ass. with?

• PH

  • Cushing’s disease, protein losing nephropathy & enteropathy, IMHA etc.

How is PTE diagnosed?

• Arterial blood gas —> largre alveolar to arterial O2 gradient

• Significant V:Q mismatch

• D dimers & fibrin degredation products identified (clot breakdown products)

How do you treat/prevent PTE?

Same as ATE

How is dirofilaria immitus spread and what conditions does it need?

• mosquito-borne; endemic in much of the world in dogs & cats

• Needs warm, moist climate to allow L1 to mature into infective L3 in a mosquito (intermediate host)

What is the lifecycle of dirofilaria immitus?

What does dirofilaria immitus cause?

Cor pulmonale, wt. loss, fatigue, cough, dyspnoea

How does dirofiliarisis present on rads & echo?

• Rads —> Lungs affected & enlarged pulmonary vessels

• Can see worms on echo

What is dirofilaria treated?

• Can surgically remove —> must remain intact when removed otherwise anaphylactic reaction poss

• Moxidectin & doxyclyine to kill Wolbachia first

• Melarsomine Dihydorchloride (but have to import) (also doxycyline first)

How is dirofilariosis diagnosed?

• Direct smear

• Microfilariae on Knott test

• Immunodiagnostic testing —> antigen ELISA test (detects F), antibody test

What are the dirofilariasis preventatives?

• Selamectin monthly topical

• Milbemycin (with praziquantal) monthly oral

• Moxidectin (advocate) (with imidacloprid) monthly topical

• Adulticides —> melarsomine dihydrochloride

What are wolbachia and how are they ass. w/ dirofilariasis?

• Obligate, intracellular, G-ve, endo-symbiotic bacteria

• Found in uterus of F dirofilaria

• Poss role in pathogenesis?

• Recommendation —> treat wolbachia w/ doxycycline prior to melarsamine

Recall the epidemiological features of angiostrongylus vasorum?

• Adults about 2cm long, found in dogs & foxes

• Slugs/ snail intermediate host

• Widespread in UK, more in south

(French heartworm)

What are the clinical signs of angiostrongylosis?

• Often young dogs

• May be asymp depending on worm burden & immune response

• Resp signs

  • Chronic / unresponsive cough

    • haemoptysis (coughing up blood / bloody mucus)

  • Pulmonary hypertension

  • Dyspnoea

  • Exercise intolerance, CHF

• Coagulopathy

  • Can have major bleeds after injury / surgery (e.g. neutering), epistaxis etc.

  • Haemoptysis / Haematemesis

• Neurological

  • May be due to aberrant migration of parasites

  • Intracranial bleed

how is angiostrongylosis diagnosed?

• Thoracic rads:

  • cor pulmonale

  • variable/patchy/mixed pulmonary infiltrates (more marked @ periph of lung field)

• Eosinophilia

• Raised B-globulins

• Angio Detect SNAP test

• Larvae in faeces (Baermann)

How is angiostrongylosis treated?

• Milbemycin (w/ praziquantel)

• Moxidectin (w/ imidacloprid)

• Fenbendazole —> kills slowly, not licensed yet (good to start on)

• +/- Prednisolone to prevent immune reaction

How is angiostrongylosis prevented?

• Moxidectin (Advocate)

• Milbemycin (Milbemax) (q. 4 wks)