cardiovascular pathology - pt 1 Flashcards
what is the function of the heart
pump sufficient volumes of blood to all organs to meet the varying metabolic needs of the animal
what are the 3 layers of the heart wall
- endocardium
- myocardium
- pericardium, visceral layer (epicardium)
what is the blood supply to the heart
- left & right coronary arteries & their branches in epicardium -> intramural arteries that penetrate myocardium
- venules & veins collect blood from heart wall & return it to right atrium via coronary sinus
what are the 3 specific characteristics to cardiac myocytes
- central nuclei
- intercalated discs
- cross-striations
what are sarcomeres
the contractile units composed of actin & myosin filaments
what are intercalated discs
specialized junctions between myocytes that allow myocardium to function as a unit
what is the cardiac conduction system composed of
modified cardiac myocytes that initate & conduct an electrical impulse -> coordinate cardiac muscle contraction
what is the function of the cardiac valves
allow unimpeded unidirectional blood flow
what are atrioventricular (AV) valves
- supported by tendinous cords (chordae tendinae) & ventricular papillary muscles
- allow flow from atria into ventricles, prevent backflow into atria
what are semilunar valves
allow flow into pulmonary artery & aorta, prevent backflow into ventricles
what is heart failure
heart is unable to meet the metabolic needs of the animal
loss of pumping efficiency due to cardiac disease or increased cardiac workload can lead to ____ & _____
ischemia and congestion
what is ischemia
decreased blood flow to the tissues
what is congestion
pooling of blood behind the failing chambers
what are gross findings of right-sided CHF
- subcutaneous edema
- ascities
- chronic hepatic congestion (nutmeg liver)
what are gross findings of left-sided CHF
pulmonary congestion & edema
what are the gross findings of right/left-sided CHF
- pleural effusion
- common in cats
what are myocardial diseases
cardiac responses to increased workload or dysfunction
- hypertrophy
- dilation
- cardiomegaly
what is hypertrophy
increase in myocardial mass due to increase myocyte size
what is dilation
increase in chamber volume due to stretching and/or hypertrophy of myocytes
what is cardiomegaly
increase in external dimensions of heart due to hypertrophy and/or dilation
what is concentric hypertrophy
- due to pressure overload
- sarcomeres added in parallel
- increase wall thickness
- decrease chamber volume
what is eccentric hypertrophy
- due to volume overload
- sarcomeres added in series
- increase chamber volume (dilation)
- normal to decreased wall thickness
what is cardiomyopathies
- diseases of the myocardium
- primary (genetic or idiopathic)
- secondary (known cause other than genetic)
what are the 3 main types of cardiomyopathies
- hypertrophic
- dilated
- restrictive
what is hypertrophic cardiomyopathy (HCM)
- common in cats (esp. young to middle-aged adult males)
- PRIMARY (heritable) in some cat breeds (known mutation in Maine coon & ragdoll, idiopathic in others)
what are the gross findings of hypertrophic cardiomyopathy (HCM)
- englarged heart (cardiomegaly)
- thick LV wall, decreased LV volume (concentric hypertrophy)
- +/- LA dilation, thrombosis
what is thyrotoxic cardiomegaly
DDX for HCM
- common in cats
- SECONDARY to hyperthyroidism
- thyroid gland hyperplasia -> increase thyroid hormone production -> increase production of myocardial contractile proteins -> myocardial hypertrophy
- potentially reversible on return to euthroidism
what are the gross findings of thyrotoxic cardiomegaly
- heart looks similar to HCM
- enlarged nodular thyroid glands
what is dilated cardiomyopathy (DCM)
- most common type in dogs (esp. young to middle-aged giant & large breed)
- PRIMARY (hertible) in some breeds (doberman, juvenile portuguese water dogs)
- SECONDARY (acquired) form due to nutritional imbalances (taurine deficiency in dogs & cats)
what are the gross findings of DCM
- enlarged rounded heart
- dilated chambers, thin walls (eccentric hypertrophy), atrophied papillary muscles
what is restrictive cardiomyopathy (RCM)
- second most common type of cardiomyopathy in cats
- endomyocardial fibrosis -> impaired ventricular filling
- sequela of ENDOMYOCARDITIS (idiopathic inflammation that often follows a stressful event)
what are the gross findings of RCM
- thick opaque endocardium (usually involving LV outflow tract)
- thick LV wall, decreased LV volume (concentric hypertrophy)
- LA dilation
what are cardiomyopathy sequelae (may include)
- arrhythmia (syncope, sudden death)
- cardiac thrombosis -> thromboembolism
- aortic (“saddle”) thromboembolism -> hind limb ischemia, paresis
- thromboemboli to other organs -> ischemia, infarcts
- congestive heart failure
what is myocardial necrosis
- death of cardiac myocytes
- myocytes have minimal capacity to regenerate
- irreversible injury -> myocyte necrosis -> inflammation & healing by fibrosis
- clinical significance determined by location and extent of injury
- may be subclinical or clinical -> arrhythmias, sudden death, CHF
what does acute myocardial necrosis look like grossly
myocardial pallor, dry +/- gritty texture (dystrophic mineralization)
what does chronic myocardial necrosis look like grossly
firm depressed myocardial scar (fibrosis)
what are the causes of myocardial necrosis
- nutritional (VE, selenium deficiency)
- toxic (ionophores)
- ischemic (coronary vasopasm, thrombosis)
- genetic (X-linked muscular dystrophy in goldens)
- traumatic
what is nutritional myopathy
- VE/selenium deficiency -> decreased antioxidant activity -> oxidative membrane damage -> cardiac & skeletal myocyte necrosis
- “white muscle disease” in ruminants & horses
- “mulberry heart disease” in pigs; accompanies by multiprgan vascular necrosis/thrombosis +/- hepatic necrosis
- tan foci of myocardial necrosis & mineralization
what is myocarditis
inflammation of myocardium
what are the gross and histological findings of myocarditis
- similar to myocardial necrosis (which may be present)
- myocytes separated/replaced by inflammatory cells
what are the causes of myocarditis
often hematogenous infection of local extension from endocardium & pericardium
- viral
- bacterial
- fungal
- parasitic
what are endocardial diseases
most clinically significant lesions affect the valves rather than the mural endocardium
what is valvular stenosis
failure to open completely
what is valvular insufficiency
failure to close completely
what is degenerative valve disease (“endocardiosis”)
- most common cardiovascular lesion in dogs
- idiopathic degeneration of valvular collagen with replacement by myxomatous matrix
- most common in smaller breeds, prevalance increases with age. earlier onset with cavalier king charles spaniel
- mitral > tricuspid»_space; aortic & pulmonic
what are the gross findings of degenerative valve disease
white, opaque, thickened/nodular valve leaflets with a smooth, glistening surface
what is myxomatous valvular degeneration
- valves thickened by loose fibroblastic tissue & wispy blue-gray matrix rich in mucopolysaccharides
- not an inflammatory lesion
what may happen with degenerative valve disease
- valvular insufficiancy: regurgiation (heart murmur)
- atrial volume overload: eccentric hypertrophy +/- CHF
- atrial subendocardial fibrosis: “jet lesion”
- atrial thrombosis: thromboembolism +/- infarcts
- chordae tendinae rupture
- atrial tear: hemopericardium
what is endocarditis
- inflammation of endocardium
- bacterial»_space; fungal or parasitic causes
- tricuspid lesions most common in cattle
- mitral lesions most common in others
what is the pathogenesis of endocarditis
- sustained or recurrent bacteremia & minor endocardial injury at lines of valve apposition
- bacterial adhesion & proliferation
- inflammation & further endocardial injury
- thrombosis
what are the gross findings of endocarditis
rough, friable, red-tan thrombi (“vegetations”) on valvular endocardium
what is vegetative valvular endocarditis
septic thombi composed of fibrin, bacteria, neutrophils +/- granulation tissue/fibrosis
what may happen with vegetative endocarditis
- death may result from valvular insufficiency (leading to CHF) or effects of bacteremia
- septic thromboemboli to heart, kidneys, brain, other organs causing: ischemia (infarcts) & infection (inflammation)
what is uremic endocarditis
- due to renal failure in dogs
- endocardial necrosis: mineralization & inflammation of LA endocardium
- pathogenesis is poorly understood
- DDX for endocardial mineralization: VD intoxication
