L29: Disease Myocardium

Question 1

What are some general implications of myocardial Dz?

Answer 1

reduced contractility 
arrhythmias 
heart failure 
Impairment of diastole 
Intra-pericardial haemorrhage 
Valvular insufficiency 
Intra-cardiac thrombosis

Question 2

What can cause hydronic or fatty degeneration of cardiac myofibres?

Answer 2

sublethal insult

e.g. hypoxia, anaemia, toxaemia, bacteraemia

Question 3

What is brown atrophy of heart ?

Answer 3

Severe intracellular accumulation of lipofuscin pigment (wear and tear pigment)

E.g. in old animals, high producing dairy cows

Question 4

What are the two main forms of mineralisation?

Answer 4

Dystrophic (deposition of mineral)

Metastatic (Vit D toxicity)

Question 5

When is the capacity for mitotic division of cardiac myofibrils lost?

Answer 5

as a neonate

Question 6

Where are areas of myocardial necrosis most likely to be found and why?

Answer 6

LV –> greatest tension during systole

Esp papillary mucules and IV septum!

Question 7

Describe how myocardial lesions appear grossly over time?

Answer 7

4hrs- microscopic 
4-12hr gross pallor 
18-24hr pale, dystrophic mineralisation, fibrin, haemorrhage 
2-4 days reactive hyperaemia 
7 d necrotic foci fibroses 
Weeks white collagen

Question 8

How long can cardiac myofibres tolerate hypoxic conditions ?

Answer 8

20-30 mins

Question 9

How are foci of myocardial necrosis repaired?

Answer 9

fibroplasia –> fibrosis

Question 10

What can cause myocardial ischaemia?

Answer 10

DIC
thrombosis/ thromboembolism of coronary arterial branches
Severe anaemia
Dilated hearts

Question 11

What is the aetiopathogeneiss of white muscle disease?

Answer 11

Nutritional myopathy + rapid growth (especially skeletal muscle)

ruminants, lambs, calves

Question 12

What are the gross lesions you’d expect in a myocardium with white muscle disease

Answer 12

pale, wet, dystrophic mineralisation, haemorrhage streaks, poor rigor mortis

Question 13

What is the aetiopathogeneisis of mulberry heart disease in pigs?

Answer 13

Vit E deficiency, especially pigs with great nutrition!

Question 14

What cardiac lesions would you expect in a pig with mulberry heart disease?

Answer 14

epicardium, myocardium, subendocardium haemorrhage

Question 15

What is myocarditis, what are some causes?

Answer 15

inflammation myocardium

bacteraemia, haematogenous parasites, viraemia.
E.g. parvo, herpes, foot and mouth, listeria, strep, black leg, toxoplasma

Question 16

What is cardiomyopathy? How do we diagnose it? !

Answer 16

chronic disease of heart muscle. Hypertrophic, dilated or restrictive.

Generally idiopathic, exclude other possible causes

Question 17

Describe hypertrophic cardiomyopathy (+ species affected + major effect on cardiac function)

Answer 17

Concentric hypertrophy due to sustained pressure overload
Diastolic failure
Cardiomegaly
Common in catties

Question 18

Describe dilated cardiomyopathy (+ species affected + major effect on cardiac function)

Answer 18

Eccentric hypertrophy due to chronic volume overload 
Systolic failure 
dilated chambers 
Dec contractility 
Inc EDV 
Dogs

Question 19

Describe restrictive cardiomyopathy (+ species affected + major effect on cardiac function)

Answer 19

Reduced ventricular compliance
impaired diastole
stiff heart
cats

Question 20

What is a common consequence of cardiomyopathy in cats?

Answer 20

thrombosis!!

Most common, saddle thrombus

Question 21

What clinical signs would alert you to a possible saddle thromboembolism

Answer 21

sudden onset bilateral hind leg paresis, muscle weakness, absence femoral pulse, cool limbs, cyanotic nail beds, ischaemic hindlimb

Question 22

What neoplasms are commonly found in the heart?

Answer 22

metastases from malignancies elsewhere

or lymphoma, haemangiosarcoma, peripheral nerve sheath tumour, myxoma, mast cell tumour, rhabdomyoma

Question 23

What would be dDx if you found multiple, small cream white foci scattered through the myocardium of an animal at necropsy? What would you need to differentiate between?

Answer 23

Neoplasia e.g. nodular lymphoma. Send to histo (slice open and squeeze to differentiate from…)
Suppurative inflammation due to haematogenous bacterial infection (will squeeze pus out)
Fibrosis of myocardium following damage (e.g. necrosis)
Dystrophic mineralisation