L29: Disease Myocardium Flashcards
What are some general implications of myocardial Dz?
reduced contractility arrhythmias heart failure Impairment of diastole Intra-pericardial haemorrhage Valvular insufficiency Intra-cardiac thrombosis
What can cause hydronic or fatty degeneration of cardiac myofibres?
sublethal insult
e.g. hypoxia, anaemia, toxaemia, bacteraemia
What is brown atrophy of heart ?
Severe intracellular accumulation of lipofuscin pigment (wear and tear pigment)
E.g. in old animals, high producing dairy cows
What are the two main forms of mineralisation?
Dystrophic (deposition of mineral)
Metastatic (Vit D toxicity)
When is the capacity for mitotic division of cardiac myofibrils lost?
as a neonate
Where are areas of myocardial necrosis most likely to be found and why?
LV –> greatest tension during systole
Esp papillary mucules and IV septum!
Describe how myocardial lesions appear grossly over time?
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
How long can cardiac myofibres tolerate hypoxic conditions ?
20-30 mins
How are foci of myocardial necrosis repaired?
fibroplasia –> fibrosis
What can cause myocardial ischaemia?
DIC
thrombosis/ thromboembolism of coronary arterial branches
Severe anaemia
Dilated hearts
What is the aetiopathogeneiss of white muscle disease?
Nutritional myopathy + rapid growth (especially skeletal muscle)
ruminants, lambs, calves
What are the gross lesions you’d expect in a myocardium with white muscle disease
pale, wet, dystrophic mineralisation, haemorrhage streaks, poor rigor mortis
What is the aetiopathogeneisis of mulberry heart disease in pigs?
Vit E deficiency, especially pigs with great nutrition!
What cardiac lesions would you expect in a pig with mulberry heart disease?
epicardium, myocardium, subendocardium haemorrhage
What is myocarditis, what are some causes?
inflammation myocardium
bacteraemia, haematogenous parasites, viraemia.
E.g. parvo, herpes, foot and mouth, listeria, strep, black leg, toxoplasma
What is cardiomyopathy? How do we diagnose it? !
chronic disease of heart muscle. Hypertrophic, dilated or restrictive.
Generally idiopathic, exclude other possible causes
Describe hypertrophic cardiomyopathy (+ species affected + major effect on cardiac function)
Concentric hypertrophy due to sustained pressure overload
Diastolic failure
Cardiomegaly
Common in catties
Describe dilated cardiomyopathy (+ species affected + major effect on cardiac function)
Eccentric hypertrophy due to chronic volume overload Systolic failure dilated chambers Dec contractility Inc EDV Dogs
Describe restrictive cardiomyopathy (+ species affected + major effect on cardiac function)
Reduced ventricular compliance
impaired diastole
stiff heart
cats
What is a common consequence of cardiomyopathy in cats?
thrombosis!!
Most common, saddle thrombus
What clinical signs would alert you to a possible saddle thromboembolism
sudden onset bilateral hind leg paresis, muscle weakness, absence femoral pulse, cool limbs, cyanotic nail beds, ischaemic hindlimb
What neoplasms are commonly found in the heart?
metastases from malignancies elsewhere
or lymphoma, haemangiosarcoma, peripheral nerve sheath tumour, myxoma, mast cell tumour, rhabdomyoma
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?
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
