Avian Cardiology

How does the avian CV system compare to mammals?

HIGHER...

- SV

- HR

- arterial BP

- CO

- heart to BW ratio

How is the avian heart structurally different from mammals?

- 3 cusps on the left AV valve

- 1 muscular flap on the right AV valve, no chordae tendinae

- ascending aorta on the right

- brachiocephalic arteries are larger than the aorta

- 2 CVCs

- muscle fibers are smaller, lack T tubules and M bands

How is the electrical activity of the avian heart different from mammals?

Depolarization goes from out to in, epicardium -> endocardium

Negative mean electrical axis on ECG and upside down QRS (except broilers and pekins)

What is atherosclerosis?

Chronic inflammatory and degenerative disease of the arterial wall causing luminal narrowing and progressive accumulation of substances

What products accumulate in the vessel lumen in atherosclerosis?

- inflammatory cells

- fat

- cholesterol

- calcium

- cellular debris

In what stage of atherosclerosis are clinical signs seen?

Once stenosis and ischemia occurs

Pathogenesis of atherosclerosis

Endothelial dysfunction/damage/oxidative stress -> accumulation of lipoproteins and monocytes -> macs store lipoproteins/cholesterol and become foam cells -> foam cells die and lipid/necrotic debris accumulate -> smooth muscle cells make a fibrous cap

Most common sites for atherosclerotic lesions

Great vessels (brachiocephalic trunks, aorta, and pulmonary artery)

Smaller arteries

Top avian species predisposed to atherosclerosis

1. Amazon parrots

2. African Grey parrots

3. Cockatiels

Risk factors for atherosclerosis

- high-fat diets (seeds, eggs, cheese, and human food)

- old

- female

- inactive lifestyle

- concurrent reproductive disease in females

- hepatic disease

- increased HDLs

Presenting complaint of a bird with CV disease

- could be none

- could be sudden death

- decreased energy level

- reduced appetite

- weakness

- exercise intolerance

- collapse or syncope

Respiratory presenting complains associated with CV disease

- dyspnea

- distended coelom

- increased resp rate or effort

- open beak breathing

- tail bob

Neurological presenting complaints associated with CV disease

- transient or persistent weakness/lameness of one or multiple limbs

- disorientation

- difficulty perching

- falling, ataxia

- tremors

- seizures

Dermatologic presenting complaints associated with CV disease

- feather plucking

- feather loss

PE findings of a bird with CV disease

- may be normal

- cachexia

- obesity

- tachypnea, dyspnea

- harsh lung sounds

- pallor or cyanosis

- tachycardia

- arrhythmia

- murmur

- poor pulse quality

- cool extremities

- coelomic distension (ascites, hepatomegaly)

- edema

- peripheral venous congestion

How does bloodwork often appear in birds with CV disease?

- may only have CBC changes if endocarditis

- may have polycythemia or signs of stress

- may have hypercholesterolemia

- may have increased HDL

Diagnostic significance of blood cholesterol levels for avian atherosclerosis

Cholesterol levels do not definitively rule in or out atherosclerosis

Normal cardiac silhouette length and width on radiographs in psittacines

51% to 61% of thoracic width on VD

35% to 41% of sternum length on lateral

How can we manage birds who are subclinical with atherosclerosis?

- fix their diet

- increase exercise

- control comorbidities

- consider GnRH agonists in females

- consider sedated exams

Primary dietary modification for managing subclinical atherosclerosis

Transition off seeds to a formulated diet with omega-3 fatty acids

Remove high saturated fats

Therapeutics if a bird is clinical for atherosclerosis

- isoxuprine

- ACE inhibitor (enalapril)

- furosemide, pimobendan, beta-blockers for CHF

- drain ascites or pericardial effusion

- O2

- analgesics

- anticonvulsants

- exercise restriction and housing modification

MOA of isoxuprine

Alpha-blocker causing peripheral vascular smooth muscle relaxation and vasodilation

Increases peripheral blood flow

Prognosis and mean survival time (MST) for birds with CV disease

Guarded to poor in birds with CHF with a mean survival time of 30 days