Path Heart III (13)

• intrinsic/principal diseases of the myocardium, as opposed to dysfunctions secondary to ischemia,
• valvular, or hypertensive diseases
• regardless of the cause (genetic, acquired, idiopathic), cardiac (ventricular) dysfunction is the key problem
• can be broken down into 3 categories: dilated (90%), hypertrophic, or restrictive (less common)
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disease solely or predominantly confined to the heart muscle

heart is a part of generalized multi-organ disorder

• Dilated Cardiomyopathy (DCM)
• progressive hypertrophy & dilation of all 4 chambers
• leads to systolic (contractile) failure
• heart enlarged to 3-4x normal size & flabby w/ dilation of all chambers
• while the cause is usually unknown (idiopathic), other conditions may be implicated (eg. infections, drugs, toxins, metabolic/neuromuscular abnormalities, etc.)
• if idiopathic it's likely to be of genetic origin affecting genes that encode cytoskeletal/sarcomere/mitochondrial proteins

• ineffective contraction
• clinically manifests as slowly progressing congestive heart failure
• symptoms: dyspnea, easily fatigable, poor exertional capacity
• in end-stage DCM cardiac ejection fraction is typically less than 25% & cardiac transplantation is the ONLY definitive treatment

• myocardial hypertrophy, abnormal diastolic filling, & in 1/3 of cases, intermittent ventricular outflow obstruction
• MASSIVE myocardial hypertrophy, usually w/o ventricular dilation
• the degree of hypertrophy is out of proportion to the hemodynamic load
• concentric hypertrophy seen in 10% of case
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• can see characteristic "banana-shaped" ventricular lumen

• missense point mutation in 1 of several genes encoding the sarcomeric proteins that form the
• contractile apparatus of striated muscle (myosin, troponin, tropomyosin etc.)
• may be related to defects in force generation that come about from altered sarcomere function
• is usually autosomal dominant however a significant portion of cases develop as sporadic mutations w/o a family history

in most cases it presents w/ asymmetrical septal hypertrophy, meaning there is a disproportionate thickening of the ventricular septum as compared with the free wall of the left ventricle

• there is myofiber disarray w/ hypertrophic & branching myocytes running in various orientations instead of the usual parallel arrangements
• there can also be interstitial & replacement fibrosis

• a disease of the myocardium characterized by a primary decrease in ventricular compliance, resulting in impaired ventricular filling during diastole
• myocardial stiffness limits diastolic filling but contractile functions remain NORMAL
• ventricles are of normal or slightly enlarged size, cavities are NOT dilated, & the myocardium is firm
• is the LEAST common category of cardiomyopathy in Western countries
• condition invariably progresses to congestive heart failure & only 10% of patients survive for 10 years

• 1. interstitial infiltration of amyloid, metastatic
• carcinoma, or sarcoid granulomas
• 2. endomyocardial diseases
• 3. storage diseases, including hemochromatosis
• 4. markedly increased interstitial tissue

• inflammation of the myocardium associated w/ myocyte necrosis & degeneration
• the inflammation is the primary cause of the disease (as opposed to a response to myocardial injury like in ischemic heart disease)
• is most common in CHILDREN between 1–10 yrs. old & can cause acute biventricular heart failure in previously individuals
• severe myocarditis can cause arrhythmias & sudden cardiac death

• 1. viral infections (most common) like coxsackieviruses; injury is caused by an immune response directed against virally infected myocardial cells
• 2. nonviral infectious myocarditis like Chagas disease (caused by Trypanosoma cruzi); others = Trichinosis, Lyme disease (Borrelia burgdorferi)
• 3. hypersensitivity & immunologically related diseases like Rheumatic fever, systemic lupus erythematosus, drug reaction (penicillin, sulfonamide etc.)

• diffuse myocardial degeneration & necrosis w/ an inflammatory infiltrate
• lymphocytic myocarditis shows infiltration of mononuclear inflammatory cells + associated myocyte injury
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• hypersensitivity myocarditis shows interstitial inflammatory infiltrate w/ eosinophils & mononuclear inflammatory cells
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• giant cell myocarditis shows mononuclear inflammatory infiltrate w/ lymphocytes, macrophages, extensive loss of muscle, & multinucleated giant cells
• chagas disease shows myofibers distended w/ trypanosomes + surrounding inflammatory reaction & individual myofiber necrosis

• a tumor of primitive connective tissue that is the most common primary tumor of the heart in adults
• it's a benign tumor often associated w/ clonal abnormalities of chromosomes 12 & 17 and is thought to arise from primitive multipotent mesenchymal cells
• most cases show up in the L atrium as a glistening, gelatinous, polypoid mass, w/ a loose myxoid stroma (stellate or globular myxoma cells) embedded in a background of abundant proteoglycans
• has characteristic vessel or gland-like structures

while the benign tumor won't metastasize, it can EMBOLIZE & causes death in 1/3 of the patients (brain embolization)

• the accumulation of excessive fluid within the pericardial cavity, either as transudate or exudate
• normal pericardial fluid is ~30-50 mL but effusion can reach several hundred mL
• can cause cardiac Tamponade, a syndrome produced by the rapid accumulation of pericardial fluid that restricts the filling of the heart

• bleeding directly into the pericardial cavity
• caused by penetrating cardiac trauma, rupture of a dissecting aneurysm of the aorta, infiltration of a vessel by tumor, rupture of cardiac wall, bleeding diathesis, etc.
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• pressure on the heart muscle which occurs when the pericardial space fills up w/ fluid faster than the pericardial sac can stretch
• because the heart is filled with fluid blood can't properly be pumped through & filtered → builds up in the veins
• during venous pressure rises progressively & linearly while arterial pressure may be normal or elevated & therefore is diagnostically unreliable

inflammation of the pericardium (the fibrous sac surrounding the heart)

• acute MI, post-infarction, uremia, chest radiation, rheumatic fever, SLE, & trauma
• is a form of acute pericarditis; has effusion fluid rich in protein & the pericardium contains primarily mononuclear inflammatory cells

• invasion of the pericardial space by MICROBES
• it causes an acute inflammatory reaction
• organization & scarring is the usual outcome
• it may lead to constrictive pericarditis

• a defect in the structure of the heart & great vessels present at birth as a consequence of faulty embryonic development
• can be caused by misplaced structures (eg. transposition of the great vessels) or as an arrest in the progression of a normal structure from an early stage to one that is more mature (eg. atrial septal defect)
• most abnormalities arise during gestational weeks 3-8 when major cardiovascular structures develop
• is seen in ~1% of live births

• Left-to-Right Shunt
• characterized by a "back-leak" of blood from the systemic to the pulmonary circulation
• the pulmonary circulation carries both the blood that legitimately entered the R atrium & ventricle but also the blood entering through an ASD (atrial septal defect), VSD (ventricular septal defect), or PDA (patent ductus arteriosus)
• 
• blood volume & pressure in the pulmonary circulation become abnormally high
• a significant shunt causes progressive damage to the pulmonary vasculature & gradual development of irreversible pulmonary hypertension

when the pressure in the pulmonary circuit ultimately exceeds the systemic pressure causing a reversal of blood flow from the R side of the circulation to the L

• a cardiac shunt that allows blood to flow from the right to the left heart
• CYANOSIS (low O₂) presents at or near the time of birth b/c poorly oxygenated blood from the right side of the heart is introduced directly into the arterial circulation
• most common: tetralogy of Fallot & transposition of the great vessels
• can see clubbing of the finger tips, polycythemia (increase in the blood circulation of RBC), or paradoxical embolism

• a cyanotic Right-to-Left Shunt that's the most common cause of cyanotic congenital heart defects
• 1. Ventral septal defect
• 2. Obstruction to the right ventricular outflow tract (subpulmonic stenosis)
• 3. Dextroposition of the aorta so that it overrides the ventricular septal defect
• 4. Right ventricular hypertrophy
• b/c of the pulmonary stenosis, blood is shunted through the ventricular septal defect into the aorta, resulting in arterial desaturation & cyanosis
• if not repaired dyspnea on exertion will present & physical development will be slowed
• there's also a risk for bacterial endocarditis & brain abscesses

total correct with surgery is possible

• a type of cyanotic congenital heart disease in which the aorta arises from the right ventricle & the pulmonary artery from the left ventricle!
• 
• the 2 circuits are separate & not compatible w/ life
• almost all infants w/ TGA have an atrial septal defect &/or patent ductus arteriosis as compensatory mechanisms
• the malformation can be corrected w/ surgery

• a local constriction that almost always occurs immediately below the origin of the left subclavian artery at the site of the ductus arteriosus
• is 2-5x more frequent in males than females & is associated w/ bicuspid aortic valves in 2/3 of the cases

• there is hypertension in the upper parts of the body but hypotension below the coarctation (aka in the lower extremities)
• upper body hypertension results in left ventricular hypertrophy, dizziness, headaches, & nosebleeds
• lower body hypotension leads to weakness, pallor, & coldness of lower extremities
• radiographs of the chest show notching (erosion) of the inner surfaces of the ribs produced by increased pressure in markedly dilated intercostal arteries
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