Intro/Heart Failure Flashcards
What is the function of the heart?
So tissues receive adequate nutrients & oxygen, & waste products are removed
What is the first organ to form in the embryo?
heart
What chambers does the heart consist of in mammals and birds?
4 chambers (2 atria & 2 ventricles)
What are the 4 cardiac valves?
- Right atrio-ventricular (tricuspid)
- L atrio-ventricular (bicuspid or mitral)
- Aortic (semi-lunar)
- Pulmonic
Which ventricle is thicker in the adult animal?
L ventricle
Systemic circulation returns…
… non-oxygenated blood from the body to the R atrium via the vena cava
From R atrium blood passes through…
…right AV valve into right ventricle
From R ventricle blood is pumped ….
…into lungs via pulmonary (pulmonic) arteries
Blood passes from L atrium to….
…L ventricle through mitral valve
From lung…
… oxygenated blood returns to the L atrium via pulmonary veins
What are the 3 layers of the heart?
- pericardium (epicardium)
- myocardium (heart muscle)
- endocardium (atria, ventricles, & valves
What needs to be removed from heart to expose epicardium (is continuous with it)?
Pericardium
What is pericardium?
Double-layered serosal mb that covers heart & proximal part of great vessels
What is the parietal pericardium?
most external & thicker layer of pericardial sac
What is the visceral pericardium?
(aka epicardium); most internal & thinnest layer of pericardial sac that intimately covers myocardium
What are 2 serosal mbs of the pericardium composed of?
thin layer of mesothelium & CT which supports blood vessels, lymphatic vessels, nerves, & adipose tissue
What does the epicardial fat generally follow?
Coronary grooves
What is the pericardial space & what does it contain?
Present btwn epicardium & pericardium. Contains small amounts of clear lubricating fluid
What can sometimes be mistaken for lesions on the epicardial surface?
prominent lymph vessels
What is the myocardium?
Muscle of the heart
How does the heart pump blood to the lungs & systemic circulation?
through contraction (systole) & relaxation (diastole)
How does the myocardial muscle compare to skeletal muscle?
they are histologically similar but not identical
What kind of muscle is the myocardium?
- involuntary, striated muscle w/ branched fibres (a nucleus in the center of the fiber) that connect to each other through intercalated disks (wht arrows), allowing them to work as a single functional unit.
- these fibres contain abundant mitochondria (only seen by electron microscopy).
- CT is present btwn cardiomyocytes
- the sarcoplasm contains myofilaments arranged in discrete bands (A, I, Z, bands) & abundant myogloblin
What is the endocardium?
thin layer internal surface of heart
endocardium of heart is equivalent to what in blood vessels?
tunica intima
Endocardium is in close contact w/?
blood
Endocardium is microscopically composed of these 3 layers:
- endothelium (superficial)
- basal lamina
- sub-endothelial CT (elastin & collagen)
Part of the conductive system & Purkinje fibres are contained in which heart layer?
endocardium
What are Purkinje Fibers?
Specialized myocardial cells that are responsible for electrical impulse conduction (not to be confused w/ Purkinje cells in cerebellum)
What do heart valves allow for?
Unidirectional blood flow
What is normal morphology of the valvular leaflets (cusps)?
They are thin, smooth, partially translucent, lined by endothelium, glistening, & elastic
How do AV valves attach to papillary muscles of ventricular myocardium?
Chordae tendinae
How to do a postmortem exam of heart?
- No universal method.
- in neonates & young animals, it’s important to carefully check for congenital heart defects
- method chosen largely depends on the species, disease suspected, & pathologist preference
- once the heart has been opened, it is recommended to gently wash away excess blood from atria, ventricles, & major blood vessels
- any abnormal change should be recorded & photographed for a second opinion if deemed necessary
What 12 things to look at on post mortem exam of heart?
- Silouette in situ
- colour
- wall thickness
- shape
- pericardial fluid
- valves
- size
- fat deposits
- endocardium
- weight (total & ratios)
- post-mortem changes
- blood vessels
What do we look for when checking the heart in situ?
pay attention to relative size of heart
Before cutting the pericardium, what should you check for?
presence of effusions or exudate
enlarged hearts are called what and occur in?
Cardiomegaly; occur in cardiac dilation or hypertrophy, pericarditis, tumors, or pericardial effusions
What is important to consider regarding cardiac damage?
- cardiomyocytes lose their ability to regenerate soon after birth - therefore healing following damage is limited
- functional reserve of the heart is reasonably good & compensatory mechanisms exist to mitigate damage
- cardiac disease does not necessarily progress to heart failure
What are the most important compensatory mechanisms of heart?
- activation of neurohumoral systems:
- decreased CO & the resulting decreased circulating blood volume lead to the release of NE by cardiac nerves causing increased HR, augmentation of cardiac contractility & increased vascular resistance (via vasoconstriction).
- similarly, there is activation of the renin-angiotensin-aldosterone system, which results in increased reabsorption of sodium & water by the kidneys & vasoconstriction
- the resulting expansion of the blood volume induces secretion of atrial natiuretic peptide; this enhances sodium & water excretion & induces vasodilation as a counter mechanism - cardiac dilation & hypertrophy
What is overall enlargement of the heart called?
cardiomegaly
What is cardiac output?
heart rate X stroke vol
What does myocardial hypertrophy cause?
Greater contractility & ejection force
MD?
myocardial hypertrophy
MD?
cardiac dilation
What is cardiac dilation in response to?
an increased workload in both physiologic & pathologic states
What does cardiac dilatation (dilation) cause?
increased stroke (blood) volume
MD?
cardiac dilation
How does cardiac dilatation (dilation) work?
- myocardial fibers stretch thereby increasing contractile force, stoke volume, & cardiac output (Frank-Starling relationship)
- increased contractile force has limit, after which increased stretch will result in decrease in tension developed
- chronic dilation of ventricle can occur through addition of sarcomeres & hence lengthening of myocytes
- acute overload leads to dilation, chronic volume overload causes hypertrophy
Two types of cardiac hypertrophy?
Primary (idiopathic) or secondary
Where can cardiac hypertrophy occur?
biventricular, right ventricle, or left ventricle
3 things about primary hypertrophy?
less common, irreversible, & mostly seen in Ca & Fe
Hypertrophy occurs in the heart, …. does not
Hyperplasia (these cells cannot multiply
How does hypertrophy develop secondarily?
due to sustained increase in cardiac workload over several days or weeks, or due to trophic signals (like hyperthyroidism)
what counts as an increased workload?
- pumping more blood (volume overload)
- pumping @ higher pressure (pressure overload)
Is hypertrophy reversible & how?
yes; if underlying workload demand is corrected
Why does cardiac hypertrophy have limited benefits in pathological states?
- Impaired intrinsic contractility, impaired ventricular relaxation, & decreased compliance
- this can cause increased end diastolic pressure & ultimately lead to heart failure
What are the two types of cardiac hypertrophy?
- Concentric: increase in myocardial mass w/ thick ventricular walls & reduced ventricular chamber volume (usually associated with pressure overload)
- Eccentric: increase in myocardial mass with enlarged ventricular chamber & relative thinning of the walls (accompanied by dilation & usually associated w/ volume overload)
Cellular stages in cardiac hypertrophy:
- Initiation: increase in cell size (by increasing the number of sarcomeres/mitochondria)
- compensation: stable hyperfunction of the heart w/ no clinical signs
- deterioration: degeneration of hypertrophied cardiomyocytes & loss of contractility followed by heart failure
How does right sided heart hypertrophy present and what are some examples?
broad base; pulmonic (arterial) stenosi, Brisket disease, pulmonary hypertension (cor pulmonale)
How does left sided heart hypertrophy present and what are some examples?
increased length; aortic & sub-aortic stenosis, feline hyperthyroidism, systemic hypertension
How does bilateral heart hypertrophy present and what are some examples?
globose (rounded); hypertrophic cardiomyopathy, various congenital heart defects (tetralogy of Fallot)
How does myocardial hypertrophy present histopathologically?
- can be hard to evaluate microscopically w/o morphometric methods (measurement of cell size)
- cardiomyocytes increase in width, nuclei increase in size, while sarcomeres, myofilaments, & mitochondria increase in number
- hyperplasia (increase in the number of cells) does not occur in heart muscle cells
What is cardiac failure?
heart is unable to pump blood at sufficient rate to meet metabolic demands of tissues
What happens when cardiac dysfunction is not properly compensated for?
- decreased CO via aorta &/or pulmonic arteries (anterograde component) -> hypotension, depression, lethargy, & syncope
- inability to adequately empty venous reservoirs (retrograde component) -> swollen abd (ascites), tachypnea, & dyspnea (resulting from pleural effusion & pulmonary edema)
What are the basic pathophysiological mechanisms in heart failure?
Pump failure, outflow obstruction, blood flow regurgitation, shunting of blood, restriction of atrial/ventricular filling, conduction disorders
Give an example of pump failure
weak contractility & emptying of chambers caused by myocardial degeneration, fibrosis, inflammation, &/or neoplasia
Give an example of outflow obstruction
vascular or valvular stenosis, systemic of pulmonic hypertension
Give an example of blood flow regurgitation
valvular insufficiency, endocardiosis, endocarditis, volume overload
Give an example of shunting of blood
congenital heart defects or persistence of fetal circulation
Give an example of restriction of atrial/ventricular filling
cardiac tamponade, pericarditis, tumour
conduction disorders
arrythmias caused by fxnal or structural abnormalities in conduction system
Where is congestive heart failure most commonly found & what are the most common signs?
- most commonly found in dogs & cattle
- signs: fluid retention, edema, venous congestion, & in some cases, cyanosis
Types of congestive heart failure?
can be unilateral (L or R) or bilateral (biventricular), & acute or chronic
Retrograde component of heart failure?
systemic/pulmonary venous stasis
Anterograde component of heart failure?
decreased cardiac output
Types of R-sided heart failure?
- pulmonic stenosis
- pulmonary hypertension
- brisket disease
- hardware disease
- pulmonary fibrosis
Types of L-sided heart failure?
- Aortic stenosis
- systemic hypertension
- mitral endocardiosis
- mitral dysplasia
- feline hyperthyroidism
Types of bilateral (or global) heart failure?
- tetralogy of Fallot
- hypertrophic
- cardiomyopathy
What is cor pulmonale?
pulmonary hypertension & R-sided heart failure secondary to pulmonary disease
Extracardiac lesions in R-sided heart failure?
Systemic venous & portal congestion & hypertension -> generalized edema, ascites, hydrothorax, & passive liver congestion (“nutmeg liver”)
What might R sided heart failure occur secondarily to?
pulmonary hypertension (as in cor pulmonale, dirofilariasis, pulmonary thromboembolism, brisket disease in Cattle, & ascites syndrome in broilers)
Extracardiac lesions in L-sided heart failure?
pulmonary venous congestion -> pulmonary edema & intra-alveolar hemorrhage -> red cells phagocytized by alveolar macrophages -> iron pigment in alveolar macrophages (“heart failure cells”)
What is the fluid accumulation in the lungs caused by left sided heart failure called?
cardiogenic pulmonary edema
pathogenesis of bilateral heart failure?
b/c the cardiovascular system is a closed circuit, failure of 1 ventricle will ultimately lead to failure of the other culminating in global or biventricular failure
How does Brisket disease occur?
High altitude leading to pulmonary hypertension -> hypertrophy RV -> R sided heart failure -> ascites & sub Q edema
Nutmeg liver
(Chronic passive congestion of liver).
Zonal pattern caused by congestion/necrosis/fibrosis of centrilobular regions.
MD?
Congestion of liver
MD?
Congestion of liver?
Mitral endocardiosis in a dog leading to L-Sided heart failure?
mitral insufficiency (valve becomes v short, thick, nodular) -> passive congestion of lung -> pulmonary edema -> intra-alveolar hemorrhages -> “heart failure cells”
MD?
mitral endocardiosis
MD?
pulmonary congestion & edema
MD?
pulmonary edema
MD?
mitral endocardiosis
