Pathology of the Cardiovascular System, Pt. 2 Flashcards
Which myopathies are most common in dogs and cats?
DOGS: dilated cardiomyopathy
CATS: hypertrophic cardiomyopathy
At which age and in which breed of dogs are dilated cardiomyopathies most common?
- young to middle-aged dogs
- giant/large breeds: Saint Bernards, Great Danes, Irish Wolfhounds, Doberman Pinschers, Portuguese Water Dogs (familial)
How does dilated cardiomyopathy look grossly?
rounded and enlarged heart —> abnormal shape, cardiomegaly with LV and RV dilated
What is eccentric myocardial hypertrophy?
increased sarcomeres within cytoplasm, aligning large cardiomyocytes with increased length and not width
Dilated cardiomyopathy cross-section:
DOGS
Hypertrophic cardiomyopathy:
CATS
- increased LV thickness
- decreased chamber size
- ischemic damage
Hypertrophic cardiomyopathy:
CATS
- cardiomegaly
- LA, LV enlargement
What can cause the areas of pallor seen in in hypertrophic cardiomyopathy?
degenerative necrosis from hypoxic damage —> extra muscle from prominent thickening of LV free wall and interventricular septum can’t get enough oxygen
(+ RV collapse)
How does hypertrophic cardiomyopathy affect the arrangement of cardiomyocytes?
variable degrees of hypertrophy causes them to be arranged in an interweaving, rather than parallel, pattern
Hypertrophic cardiomyopathy, interweaving pattern:
myocardial disarray
What are some common presentations of hypertrophic cardiomyopathy?
- sudden meowing and rolling —> uncomfortable, in pain!
- mouth breathing
- heart murmur
- posterior paresis/paralysis
- cold right front limb and both hindlimbs
Hypertrophic cardiomyopathy:
- marked cardiomegaly
- lungs congested and edematous
Why does the left atrium become enlarged in hypertrophic cardiomyopathy?
congestive left-sided heart failure
(hypertrophic —> >38g heart, usually no more than 16g)
Where are saddle thrombi most commonly found? Why? What does this commonly cause in cats with hypertrophic cardiomyopathy?
bifurcations (from abdominal aorta into external iliac arteries)
bifurcations have increased turbulence
ischemic damage to legs causes paresis and no/subtle femoral pulse
What causes myocarditis?
secondary cardiomyopathy often the result of hematogenous infection
- VIRAL: canine parvovirus, foot and mouth disease virus, encephalomyocarditis virus
- BACTERIA: Histophilus somni, Clostridium chauvoei
- PARASITE: Toxoplasmosis, sarcocystosis, neosporosis, encephalitozoonosis (lab animals), Trypanosoma cruzi, cysticercosis, trichinosis
Black leg, cattle:
etiology = Clostridium chauvoei
- emphysematous
Acute necrotizing and suppurative myocarditis, heifer:
common in feedlot cattle (H. somni) —> stress —> immunocrompromization
- can cause thrombotic meningoencephalitis + fibrinous pneumonia, arthritis
What is the common etiologic agent of acute necrotizing and supperative myocarditis in feedlot cattle?
Histophilus somni
- vasculitis —> thrombosis —> ischemia
- ring of inflammation around infarct
Chronic suppurative myocarditis CHF, heifer:
survival after acute onset leads to neutrophil invasion and abscess formation —> clinical signs of CHF
- etiology = H. somni
What causes cysticercosis? Where are the different stages of this parasite found?
larval stage of a taenia (platyhelminth), or tapeworm
ADULT = intestine of the definitive host (humans, dogs, wild carnivores)
LARVAL (cysticercus) = muscle of intermediate host (pigs, cattle, moose, reindeer)
What causes (neuro)cysticercosis in humans?
ingestion of taenia eggs, NOT from ingestion of larva (cysticerci) from raw or incompletely cooked pork or contaminated vegetables
- formation of tapeworm in the intestine
Cysticercus cellulosae (Taenia solium of humans), pig heart muscle:
vesicles containing Taenia
- death of the parasite within the vesicle can cause calcification
What are 4 common primary cardiac neoplasias?
- rhabdomyoma/rhabdomyosarcoma - in striated muscle, most common in skeletal muscle
- Schwanomma - Schwann cells of cardiac verves
- hemangiosarcoma - endothelial cells (rupture leads to hemopericardium and cardiac tamponade)
- heart base tumors
What are the 2 types of primary heart base tumors?
- aortic body tumors- chemodectoma involving chemoreceptors in aorta
- tumors arising from ectopic thyroid or parathyroid tissue
When are secondary cardiac neoplasias most common?
cattle with metastatic tumors, including lymphosarcoma
Atrial hemangiosarcoma, dog:
large, nodular cyst filled with blood that can rupture and bleed into the pericardial sac
Where do hemangiosarcomas arise from?
endothelium —> presence inside vessels allows for metastasis into the lungs
Atrial hemangiosarcoma, dog:
What dogs are prone to developing chemodectomas?
Boxers
- heart base tumor at the base of the aorta
Enzootic leukosis, Holstein cow:
lymphosarcoma —> increased metastasis
Enzootic leukosis, Holstein cow:
nodular, pale tan, thickened
Enzootic leukosis lesion and histology, Holstein cow:
Lymphosarcoma, Sheltie:
What is a common etiology of vasculitis in pigs? How does this present?
Erysipelothrix rhusiopathiae
multiple cutaneous infarcts - diamond skin disease
- blood vessel inflammation (vasculitis, arteritis) —> multifocal necrotizing dermatitis due to bacterial thrombi and infarcts
What is beagle pain syndrome? Where is this commonly found?
idiopathic (immune?) necrotizing polyarteritis common in juveniles
small arteries, mainly in pulmonary and meningial arterioles
What is beagle pain syndrome? Where is this commonly found?
idiopathic (immune?) necrotizing polyarteritis common in juveniles
small arteries, mainly in pulmonary and meningeal arterioles
In what animals is fibrinoid necrotizing arteritis common? What 2 things can this cause?
swine
- Mulberry heart disease
- gastric submucosal blood vessels in edema disease
Mulberry heart disease:
smooth muscle of tunica cannot be recognized
- homogenous eosinophilic fibrin
- fibrinoid necrotizing arteritis
Edema disease:
edema of stomach wall in gastric submucosal blood vessels
- Shiga toxin of E. coli
- fibrinoid necrotizing arteritis
What causes edema disease in pigs? What secondary condition can be caused?
bacterial enterotoxin (verotoxin, Shiga) that causes endothelial injury in arterioles resulting in fluid loss and edema
focal bilaterally symmetrical encephalomalacia (cerebrospinal angiopathy of swine)
Edema disease, swine:
translucent edema
What is arteriosclerosis? What is the most important pattern of arteriosclerosis? What is characteristic of this?
“hardening of the arteries” - generic term for the thickening and loss of elasticity of arterial walls, causing the lumen to shrink
atherosclerosis - presence of atheromas plaques within the intima and media containing cholesterols and other lipids
What is the most common cause of artherosclerosis? 2 other causes?
***hypothyroidism
- type II diabetes mellitus
- hyperadrenocorticism
What is this? What is the most common cause?
coronary artherosclerosis —> prominent, pallor coronary arteries with reddish plaque lesions
hypothyroidism
Coronary atherosclerosis, dog:
thick, pallor arteries
Atherosclerosis, histology:
- cholesterol cleft/mineralization
- presence of macrophages with lipids in cytoplasm (vacuoles)
Coronary atherosclerosis:
not as obvious
Coronary atherosclerosis, histology:
- extreme thickening of arterial wall
- macrophages with lipids in cytoplasm
- focal mineralization; cholesterol clefts
What are 3 common causes of arterial mineralization in cows, horses, and pigs?
- Johne’s disease - granulomatous inflammation due to Mycobacterium bovis causes macrophages to produce substances that induce calcium deposition
- ingestion of calcinogenic plants containing vitamin D analogs - vitamin D increases calcium deposition in the intestine, leading to deposition into major arteries
- unintended overdosing of vitamin D in feed
Arterial mineralization, cow:
What are dissecting aneurysms?
dissection of blood between and along the laminar planes of the tunica media causes the formation of a blood-filled channel within the aortic wall, resulting in rupture and fatal hemorrhage
What are dissecting aneurysms?
dissection of blood between and along the laminar planes of the tunica media causes the formation of a blood-filled channel within the aortic wall, resulting in rupture and fatal hemorrhage
What is the most common cause of arterial ruptures leading to aneurysms?
physical trauma
- sponateous ruptures are rare
When is fatal rupture of the uterine artery common in mares?
during parturition of aged mares with low serum copper levels
(copper is necessary for blood vessel wall health)
When is rupture of the carotid artery in horses common?
mycotic vasculitis in the guttural pouch, since the medial wall of the pouch is attached to the carotid artery and fungi have a predilection for blood vessels
When is aortic rupture common in horses? What is it thought to be secondary to? Where in the aorta is this rupture commonly found?
in periods of excitement and physical activity, like racing, showjumping, or breeding in stallions (however, most cases are idiopathic)
increased intra-aortic pressure at the root of the aorta
What breed of horse has a high prevalence of aortic rupture? Where does the rupture occur?
young Friesian horses
aortic arch, potentially with aortopulmonary fistulation
Aortic rupture, horse:
What is a common cause of dissecting aneurysms in pigs?
copper deficiency
- dilated pulmonary artery
- dark red = blood pooling and splitting the wall
Dissecting aneurysm, turkey:
- abdominal aorta
- blood pools and splits tunica media
Where are dissecting aneurysms also reported in racing greyhounds?
coronary and renal arteries —> fatal arterial rupture
What is the Virchow triad?
- endothelial injury
- hypercoagulability
- abnormal blood flow
- all leads to thrombosis
How does arteritis lead to thrombosis?
inflammation of arterial walls leads to damage of endothelial surface
Vasoconstriction and primary hemostasis:
Platelet plug formation:
What antithrombotic event occurs in healthy endothelium to keep a thrombus from forming?
release of tissue plasminogen activator (fibrinolysis) and thrombomodulin (blocks coagulation cascade)
What are 2 common results after a thrombus has formed within the vessel?
- thrombus propagation - platelet and coagulation pathway activation increases the size of the thrombus
- recanalization- formation of a blood channel through the thrombus so that RBCs can flow through
What is the main complication associated with thrombus formation?
piece of thrombus becomes loose and is able to travel downstream and become lodged in smaller diameter vessels —> emboli!
Why is thrombosis common in dogs with renal glomerular disease?
protein-losing nephropathy (through urine) causes a significant loss of antithrombin III, a major inhibitor of thrombin
(heartworm can cause thrombosis, too!)
How can a thrombus be differentiated from a blood clot?
paler and duller than a blood clot, that is usually bright red and moist
Strongyloidiasis, horse colon:
- parasitic colitis
- red nematodes cause infection that can lead to thrombosis
- small red pinpoints = small larval strongyloids
Colonic edema, horse:
small strongyles (cyathostome larvae) encysted in the mucosa
What is a common predilection for thrombosis caused by parasitic infection in horses? What does this typically lead to?
cranial mesenteric artery - supplies colon and cecum (associated with antiparasitic resistance)
poor perfusion leads to colic or infarction that can lead to septic peritonitis
Strongyle thrombus:
- strongyles climbing to the aorta, causing thickened and dilated aorta (verminous aneurysm)
- thrombus obliterating lumen of cranial mesenteric artery, which leads to infarction
(thrombus = dry, friable)
Verminous arteritis, abdominal aorta:
thrombus formation
Verminous arteritis in cranial mesenteric artery, histology:
- fibrin and tunic intima destruction
- prominent inflammatory infiltration of eosinophils (parasite!)
Saddle thrombosis, cat with hypertrophic cardomyopathy:
bifurcation of terminal aorta and iliac arteries
