Cardio Pathology Flashcards
Describe the cardiac skeleton
Four fibrous rings, fibrous triangle, and fibrous or membranous part of the septum that supports all the cardiac mm and valves at the heart base
How does the cardiac skeleton material differ between species?
- Dense fibrous CT - pigs and cats
- Fibrocartilage - dogs
- Hyaline cartilage - horses
- Bone (os cordis) - large ruminants
When does most coronary arterial blood flow occur?
During diastole
What is the most common cause of dysrhythmias?
Injury to atrial or ventricular myocytes, resulting in independent repeated depolarization
What is another name for the epicardium?
The visceral pericardium or visceral layer of the serous pericardium
What substance can be found contained within atrial myocytes?
Atrial natriuretic factor - this is released on dilation/stretching of the atria
Cardiac myocytes lack plasticity, meaning they have a limited ability to respond to what?
Physiologic stress, such as atrophy, hypertrophy, degeneration, necrosis or fibrosis
What three things are required for the development of hypertrophy?
Time, a healthy myocardium and adequate nutrition and oxygenation of myocardium
Describe cardiac syncope
- Acute cardiac failure
- leads to arrhythmias, massive necrosis, and extreme changes in BP/HR
- C/S - collapse, loss of consciousness, DEATH
What is the difference between forward and backward failure with CHF?
- Forward: decr flow to periph tissues
- Backward: accumulation behind the failing chamber
Describe the cycle of cardiac decompensation
- Hypoxia —> Renin release (RAAS) from kidneys —> stim aldosterone release from adrenal cortex —> Na and H2O retention —> incr plasma volume —> edema
- Edema —> stim erythropoiesis (EPO) —> polycythemia —> incr blood viscosity
Result: failing heart must pump a greater volume of thicker fluid
What two things can lead to cardiac hypertrophy?
Chronic pressure overload and chronic volume overload (also leads to ventricular dilation)
What things might cause physiologic cardiac hypertrophy?
- It’s a reversible response to exercise or pregnancy, without any deleterious effect
- initiated by thyroid hormone, insulin, insulin growth factor 1 and GH
What is the difference between preload and afterload?
- Preload- the end diastolic volume that stretches the ventricle to its greatest dimensions
- Afterload - pressure that the chamber of the heart must generate to eject blood out of the heart
Describe concentric cardiac hypertrophy
- An incr in mass of the ventricle w/o accompanying incr in end-diastolic volume, often w/ decr in ventricular lumen
- caused by increased afterloads (systolic loads)
- e.g. aortic/pulmonic stenosis, PDA, cats with hyperthyroidism
What are the gross changes seen with concentric cardiac hypertrophy?
Incr thickness of wall of affected chamber, marked incr in size of papillary mm and trabeculae carnae, and right side —> incr size of moderator band
Describe eccentric cardiac hypertrophy
- An incr in myocardial mass accompanied by incr end-diastolic volume (dilated chamber)
- b/c of dilation, thickness of involved ventricular wall is usually no more than normal
-
caused by an incr in diastolic load (incr preload)
- e.g. AV or semilunar valvular insufficiencies, arteriovenous shunts
Describe the gross pathological changes seen with eccentric cardiac hypertrophy and dilation
Heart tends to be globose —> even though mass is incr, the wall is usually thin, papillary mm may also be attenuated
What is the best indicator of dilation of the atria?
Subendocardial fibrosis
What are two reasons the heart can fail?
Because of impaired pump function and/or because of increased cardiac work demands
What is congestive heart failure?
-
Chronic loss of pumping ability –> Vascular congestion and edema within the interstitium of tissues and body cavities (chronic)
- syndrome NOT a dz
- eventual progression to full failure
Define acute heart failure
Intermittent weakness and syncope caused by substantial change in heart rate or rhythm —> results in drop of precipitous cardiac output —> sudden unexpected death
What are the causes of left sided heart failure?
- Myocardial loss of contractility (myocarditis, myocardial necrosis, cardiomyopathy)
- valvular insufficiency (mitral/aortic valve)
- aortic stenosis
- systemic hypertension
What are the sequelae and clinical signs of left sided heart failure?
Seq: Pulm congestion/edema/fibrosis and hemosiderosis (heart failure cells)
C/S: cough, dyspnea
Where does the place of peripheral edema caused by right sided heart failure differ between species?
- Ruminants and horses—> dependent subcutaneous edema
- Dogs —> peritoneal cavity (ascites)
- Cats—> thorax (hydrothorax)
True or False: renal complications occur more frequently with right heart failure than with left heart failure
True; leads to incr blood volume, peripheral edema and more marked azotemia
What are the causes of right sided heart failure?
- Valvular insufficiency (incr preload) - tricuspid, pulmonary
- pulm hypertension (incr afterload) - obstruction of forward flow
- pulmonic stenosis
What are the sequelae of right sided heart failure?
- Hepatic congestion - passive congestion (nutmeg liver)
- ascites (dogs)/hydrothorax (cats)
- pleural and pericardial effusion
- congestion of stomach and intestines—> may impair function —> manifest as diarrhea, splenomegaly
What does the liver look like histologically with right sided heart failure?
Sinuosoids are dilated/congested, atrophy of hepatocytes around central veins
What is cor pulmonale?
- Right heart failure secondary to chronic obstructive pulmonary dz
- could be d/t dirofilariasis, PTE, neoplasia
What are some congenital heart defects in dogs?
PDA, pulmonic stenosis, subaortic stenosis
What are some congenital heart defects in cattle?
Atrial and ventricular septal defects (VSDs), transpositions of main vessels
What are some congenital heart defects in pigs?
Subaortic stenosis, endocardium cushion defects
What are some congenital heart defects in cats?
Endocardial cushion defects, mitral valve insufficiency
What are the four malformations that can cause left to right shunting?
Atrial septal defects, atrioventricular septal defects, ventricular septal defects, PDA
Why is a postnatal probe patent foramen ovale not considered an atrial septal defect?
Because it is functionally closed during development, even if it’s anatomically patent
What are some examples of atrial septal defects?
Sinus venous defect, ostium primum defect, and ostium secundum defect (most common)
What are the consequences of atrial septal defects?
Excessive flow from L to R atrium —> volume overload of RV—>dilation —> elevated CVP —> possible pulm hypertension —> RV hypertrophy —> eventual cyanosis
Describe AV septal defects
AKA endocardial cushion defects or AV canal defects
- ostium primum defect (partial AV canal)
- VSD w/ a cleft in the right AV valve (common)
- frequent in pigs w/ congenital heart dz and in cats
Ventricular septal defects are one of the most common defects in domestic animals.
T or F: most VSD are single and involve the membranous septum
True
What are the consequences of VSDs?
Postnatally - pulm vascular resistance normally drops after birth and leads to left-to-right shunting —> RV and LV pressure equalize —> both ventricles hypertrophy (eccentric) —> eventually pulm hypertension can lead to shunt reversal—> R to L—> cyanosis —> death
What is an Eisenmenger complex?
VSD cases w/ reversal and R to L shunting
At how many days after birth can you officially diagnose a ductus arteriosis as a PDA?
After 5 days
What are the 3 broad anatomical division of the heart?
Mural and valvular endocardium, myocardium and pericardium
What are the 3 general rules of mural and valvular endocardial defects?
- Valvular insufficiency incr the preload to a ventricle
- Semilunar valvular stenosis, outflow tract stenosis, and hypertension incr the afterload on the ventricle
- AV valvular stenosis and pericardial disorders decr preload on the ventricles
When might you see subendocardial hemorrhage?
- Septicemia
- endotoxemia
- anoxia
- electrocution
- trauma
- agonal change
When might you see subendocardial mineralization?
- Dystrophic (necrotic tissue) or metastatic mineralization (normal tissue w/ hyperCa)
- vit D toxicity
- calcinogenic plant toxicosis in cattle
- Ca/P imbalance
- Johne’s dz
Describe vegetative valvular and mural endocarditis
- Bacteria >>> parasites (Strongylus vulgaris) > fungi
- Gross: valves have large, adhering, friable yellow-to-gray masses of fibrin ( (= vegetations)
- can occlude valvular orifice and there is frequently valvular involvement (mitral>aortic>tricuspid>pulm)
What is Virchow’s triad of thrombogenesis?
Endothelial injury, turbulence, hypercoagulability
What is the pathogenesis of vegetative valvular and mural endocarditis?
- Involves Virchow’s triad
- affected animals often have pre-existing extracardiac infections
- often septic emboli that lodge in heart,kidneys
What are the causes of endocarditis?
- Sepsis (vegetative, valvular, Strep, Staph, Klebsiella, E. Coli)
- Uremia (ulcerative, LA)
- can result in embolism of various organs (ie. kidney)
Describe uremic endocarditis
Occurs in dogs d/t acute or repeated episodes of uremia
- ulcerative and targets the left atrium
What are 4 diseases that distort valves?
- Endocardiosis
- valvular stenosis
- valvular dysplasia
- hematocysts and lymphocysts
What is endocardiosis and what type of animals does it target?
Myxomatosis valvular degeneration (mitral > tricuspid)
- targets small and toy breeds and middle-aged to older dogs
- Cavies are predisposed
What are some possible sequelae of endocardiosis?
Valvular incompetency, CHF (R or L), atrial dilation, jet lesions, LA rupture —> hemopericardium, chordae tendinae rupture
Describe hematocysts and lymphocysts
Occur commonly in ruminants, do not cause problems, and regress within a few months of birth
Name 3 common myocardial diseases
Myocardial necrosis, myocarditis, and cardiomyopathies
What are four potential causes of myocardial necrosis?
- Infectious
- nutritional myopathies
- exertional myopathies
- toxins
What are 3 nutritional causes of myocardial necrosis?
- Vitamin E and Selenium deficiency (lambs, calves, swine - mulberry heart dz, horses)
- Thiamine deficiency (carnivores)
- Copper deficiency (falling syndrome in AUS/Fl, death)
What are some gross and histologically features seen with vitamin E and selenium deficiency-induced myocardial necrosis?
- Pallor = areas of necrosis
- mineralization of necrotic myofibers
What are some toxins that cause myocardial necrosis?
- Monensin (ionophore used as a cocciostat in ruminants)
- Plants (cardiac glycoside containing plants)
- Drugs (Doxorubicin)
Describe brain-heart syndrome
Subendocardial necrosis seen following acute brain/CNS injury
- caused by coronary artery spasm or excess catecholamine release/functional pheochromocytoma
Describe myocarditis
Inflammation of the myocardium
- typically spread hematogenously
- can result in acute death from focal myocarditis resulting in conduction abnormalities or can lead to CHF
What are some causes of myocarditis?
- Viruses (canine herpesvirus, parvo, FMD)
- bacteria (actinobacillus, bartonella)
- Protozoa (Neospora, Sarcocystis)
- helminths (Trichinella spiralis)
Describe cardiomyopathies
Genetic abnormalities of myocardial contractile, cytoskeleton or mitochrondrial proteins
- can be responsive to substances such as taurine or carnitine
Describe dilated cardiomyopathy
Genetic abnormalities in cytoskeletal proteins and mitochondrial genes, characterized by dysfunction of systolic phase of cardiac cycle
- both atria and ventricles are dilated
Describe hypertrophic cardiomyopathy
-
Diastolic dysfunction - hypertrophied ventricle is less stiff, resulting in impaired filling
- commonly inherited as autosomal dominant w/ high prevalence of subclinical dz or sudden death
Describe what myocytes look like microscopically with hypertrophic cardiomyopathy
Hypertrophied and arranged in a whirled or disorganized pattern
Describe restrictive cardiomyopathy
- Impaired filling d/t diastolic dysfunction
- interstitial or endomyocardial fibrosis
- occurs most frequently in cats
Describe HCM in cats
Inherited autosomal dominant trait in Maine Coons and Ragdolls
- Gross - enlarged heart, massive symmetrical concentric hypertrophy of both ventricles (LV most severe typically)
- does not = concentric hypertrophy secondary to hyperthyroidism
Describe RCM in cats
- Less common than HCM
- also called LV endocardial fibrosis
- may be preceded by endomyocarditis
- seen in older cats with left sided or bilateral heart failure - murmurs and arrhythmias are common
Describe the gross and histopathological lesions you see with RCM
- Gross - severe endocardial thickening w/ mural thrombosis
- Histo - replacement of endocardium and myocardium by granulation tissue and fibrosis +/- macrophages, lymphocytes, plasma cells
- Bartonella infections and hypereosinophilic syndrome are common causes
Describe DCM in cats
- Associated with taurine deficiency, less prevalent
- Gross lesions: all ventricles are dilated and flabby with thin walls, endocardium may be pale d/t fibrosis
Describe the condition of having excessive moderator brands
Not technically a cardiomyopathy - likely a congenital defect of older cats
- excessive moderator bands (false tendons) in LV bridging the ventricular septum to the free wall—> heart failure and death
Describe DCM in the dog
- Young to middle aged giant and large breed dogs (ie. Dobies, St. Bernards, Irish wolfhounds, Great Danes)
- genetic basis - may be X linked
- heart failure, short onset of C/S, may see unexpected death
What are the gross lesions seen in a dog with DCM?
L-sided CHF, biventricular failure, all chambers are dilated +/- subendocardial fibrosis, atrial fibrosis
What are some common bovine cardiomyopathies?
- DCM in Holsteins, Japanese black calves
- Cardiomyopathy assoc. w/ tightly curled “wooly” haircoat in polled and horned Hereford calves
- HCM in Holsteins
Describe hydropericardium
Excess of clear fluid in pericardial sac - generalized anasarca (edema)
- causes include - hypoalbuminemia, CHF, neoplasia
- fluid accumulates slowly allowing stretch of pericardium
Describe hemopericardium
Accumulation of pure blood in pericardial sac that rapidly results in death
- if blood is clotted —> true hemopericardium
- can be due to cardiac rupture or direct trauma
Describe the pathogenesis of hemopericardium in horses vs. dogs vs. swine
- Horses: rupture intrapericardial aorta or atria
- Dogs: atrial rupture d/t endocardiosis, atrial hemangiosarc, ulcerative atrial endocarditis of renal failure
- Swine: rare, rupture of heart (atrium), coronary artery, aorta
What are the microorganisms responsible for fibrinous pericarditis?
Usually result of hematogenous microbial infections
- Cattle - pasteurollosis, blackleg
- Swine - Glasser’s dz (Haemophilus)
- Horses: Mycoplasma, mare repro loss syndrome
- Cats: rare, assoc w/ FIP
What causes purulent pericarditis?
- Almost solely occurs in cattle as a result of traumatic perforation from FB originating in the reticulum —> can lead to chronic constrictive pericarditis and severe cardiac dysfunction
- also seen in cats and horses w/ pyothorax
- migrating grass awns in western US = another cause
What are some neoplasms of the heart?
Primary tumors are rare, but mets to the myocardium are common
- primary tumors of the aortic body (chemodectomas) and ectopic thyroid and parathyroid tumors may arise at heart base in dogs
- Also rhabdomyomas, metastatic lymphomas
What is a rhabdomyoma?
Anomalous formations of perinatal cardiac myocytes
- swine - possible Purkinje cell origi
- rare but most common in pigs >> cattle, sheep, dogs
