Download Pathology Chapter 12 - Selected Portions Part II Friday, January 18

Pathology Chapter 12 - Selected Portions Part II
Friday, January 18, 2013
10:54 AM
Hypertensive Heart Disease to Cardiomyopathies
1. Hypertensive Heart Disease
a. Stems from increased workload from hypertension which results in pressure overload and
ventricular hypertrophy.
b. Systemic (left-sided) Hypertensive Heart Disease
i.
Hypertrophy is adaptive response to pressure overload.
ii.
Minimal Criteria for diagnosis
1. Left Ventricular Hypertropy in absence of other cardiovascular problems
2. History or pathologic evidence of hypertension
a. Even low levels of hypertension, if prolonged, cause hypertrophy.
iii.
Morphology
1. Hypertension induces left ventricular pressure overload hypertrophy, initially
without dilation.
a. This wall thickening increases the weight disproportionately to the
increase in overall cardiac size.
b. Thickness = stiffness to the ventricle which impairs diastolic filling.
2. Earliest change is an increase in the transverse diameter of myocytes.
iv.
Is usually asymptomatic and comes to attention due to atrial fibrillation induced by
left atrial enlargement or CHF.
v.
Based on Severity, duration, and basis of hypertension a patient may
1. Enjoy normal lifespan
2. Develop IHD (Ischemic Heart Disease) due to hypertension on coronary
atherosclerosis
3. Suffer renal damage or cerebrovascular stroke
4. Experience progressive heart failure or SCD
c. Pulmonary (right-sided) Hypertensive Heart Disease (Cor Pulmonale)
i.
Stems from pressure overload of the right ventricle and usually has
1. Right ventricular hypertrophy
2. Dilation
3. Potential failure secondary to pulmonary hypertension
ii.
Most frequent causes are disorders of the lungs
1. Pulmonary Venous Hypertension most commonly occurs as result of Left-Sided
Heart Diseases.
iii.
Acute cor pulmonale can follow massive pulmonary embolism while chronic cor
pulmonale results from right ventricular hypertrophy (and dilation) secondary to
prolong pressure overload.
iv.
Morhphology
1. Acute: Marked dilation of RV WITHOUT hypertrophy.
2. Chronic: Right ventricular wall thickens.
a. Thickening could also be in the outflow tract, below pulmonary valve, or
moderator band.
3. Normal: Myocytes of the RV have no arrangment.
4. Right Ventricular Hypertrophy: Fat disappears and the myocytes align
themselves circumferentially.
2. Valvular Heart Disease
a. Stenosis: failure of a valve to OPEN completely, which impedes forward flow.
i.
Generally leads to pressure overload.
ii.
Few disorders produce this.
b. Insufficiency: failure of a valve to CLOSE completely, allowing reverse flow
i.
Generally leads to volume overload
ii.
Can result from intrinsic disease of the valve cusps or damage to/distortion of
supporting structures.
c. Functional Regurgitation: Incompetence of a valve stemming from a defect or abnormality
in one of its support structures.
i.
Example given of hypertrophy pushing opposite papillary muscle out of alignment
which impedes the valve from closing correctly.
d. Clinical consquences of valve dysfunction vary depending on the valve, degree of
impairment, how fast it develops, and rate and quality of compensatory mechanisms.
e. Ejection of blood through narrowed stenotic valves can produce high speed "jets" of blood
that injure the endocardium where they impact.
f. Acquired stenoses of the aorta and mitral valves account for about 2/3 of all valve disease.
g. Most frequent causes of Major Functional Valvular Lesions are:
i.
Aortic Stenosis from calcification and/or congenitally bicuspid valves.
ii.
Aortic Insufficiency: dilation of aorta related to hypertension and aging
iii.
Mitral Stenosis: rheumatic heart disease
iv.
Mitral Insufficiency: mitral valve prolapse (myxomatous degeneration)
h. Valvular Degeneration Associated with Calcification
i.
High levels of stress on valves comes from
1. 40 million cardiac contractions per year.
2. Substantial tissue deformations during contraction
3. Transvalvular pressure gradients in the closed phase of each contraction
ii.
Calcific Aortic Stenosis
1. Most common of all valvular abnormalities that usually comes with normal wear
and tear of age.
a. Usually seen in seventh to ninth decades of life.
2. Recent studies show chronic injury due to hyperlipidemia, hypertension,
inflammation, and other factors implicated with athersclerosis.
3. Instead of accumulating smooth muscles cells, valves contain cells like
osteoblasts that make bone matrix proteins and promote calcium salt
deposition.
4. Morphology:
a. Mounds of calcified masses within the cusps that eventually protrude
through outflow surfaces into the sinuses of Valsalva which prevent cusp
opening.
i.
Process begins in valvular fibrosa at the points of max flexion near
the points of attachment.
b. Functional valve area decreased by large nodular calcific deposits that
cause tons of obstruction to outflow.
5. Clinical Features
i.
a. Obstruction of left ventricular outflow leads to gradual narrowing of the
valve orifice and increased pressure gradient across the valve.
b. Hypertrophied muscle tends to be ischemic due to diminished perfusion.
i.
Systolic and Diastolic function may be impaired, followed by
decompensation and CHF.
iii.
Calcific Stenosis of Congenitally Bicuspid Aortic Valve
1. Most frequent CONGENITAL cardiovascular malformation in humans.
2. They are predisposed to progressive degenerative calcification.
3. Responsible for about 50% of cases of aortic stenosis in adults and have been
shown to have genetic familial clustering (runs in families)
4. Only have two functional cusps, usually unequal, with the larger cusps having a
midline raphe (groove, ridge, or seam) resulting from incomplete separation of
what would have been two of three cusps.
a. This raphe is a major site of calcium deposition.
iv.
Mitral Annular Calcification
1. Calcific deposits develop in the fibrous ring (annulus) of the mitral valve and
appear as irregular, stony hard, occasionally ulcerated nodules.
2. DOES NOT USUALLY AFFECT VALVULAR FUNCTION
a. Unusual cases may lead to
i.
Regurgitation by interfering with contraction of the valve ring
ii.
Stenosis by impairing opening of mitral leaflets
iii.
Arrhythmias and death by penetration of calcium deposits deep
enough to impinge on the AV conduction system.
3. Nodules are a good place for thombi so patients have increased risk of stroke
and also for infective endocarditis.
4. Most common in women over age 60 and people with mitral valve prolapse.
Mitral Valve Prolapse (Myxomatous Degeneration of the Mitral Valve)
i.
One or both mitral leaflets are floppy and prolapse, or balloon back, into the LA during
systole.
ii.
Morphology
1. Affected leaflets are often enlarged, redundant, thick, and rubbery.
2. Associated tendinous cords may be elongated, thinned, or even ruptured, and
the annulus may be dilated
3. Primarily there is attenuation (reduction of force) of the collagenous fibrosa
layer, on which the structural integrity of the leaflet depends, along with
thickening of the spongiosa layer.
4. Secondary changes reflect stress and injury
a. Fibrous thickening of leaflets
b. Linear fibrous thickening of left ventricular surface where the abnormally
long cords snap or rub against it
c. Thickening of the mural endocardium of LV or LA from friction-induced
injury induced by the prolapsing leaflet
d. Thrombi on the atrial surfaces of the leaflets or atrial walls
e. Focal calcifications at the base of the posterior mitral leaflet.
iii.
Pathogenesis
1. Uncommonly, MVP is connected to Marfan Syndrome, which is usually caused
by mutations in fibrillin-1 (FBN-1)
2. Excess TGF-β can cause structural laxity and myxomatous (prolapse) change.
iv.
j.
Clinical Features
1. Discovered incidentally by detection of midsystolic click on physical exam.
2. About 3% of people with MVP develop one of four serious things
a. Infective endocarditis
b. Mitral Insufficiency, sometimes with chordal rupture
c. Stroke or other systemic infarct from embolism of leaflet thrombi
d. Arrhythmias (ventricular and atrial)
3. MVP is the most common cause for surgical repair or replacement of the mitral
valve.
Rheumatic Fever and Rheumatic Heart Disease
i.
Acute, immunologically mediated, multisystem inflammation a few weeks after an
episode of Group A streptococcal pharyngitis.
1. Rarely follows infections by streptococci at other sites, such as the skin.
ii.
Valvular abnormalities are key manifestations of RHD.
iii.
Characterized mainly by deforming fibrotic valvular disease, particularly mitral
stenosis (practically the only cause of mitral stenosis).
iv.
Morphology
1. Focal inflammatory regions in various tissues
a. Heart - Aschoff Bodies consisting of foci of lymphocytes, plasma cells and
plump macrophages (Anitschkow Cells)
i.
Macrophages have lots of cytoplasm and central round-oovoid
nuclei in which the chromatin is slender and wavy, like ribbons,
which give them the name "Caterpillar Cells".
2. Diffuse inflammation and Aschoff Bodies may be found in any of the three
layers of the heart, causing pericarditis, myocarditis, or endocarditis
(pancarditis)
3. Inflammation of endocardium and left-sided valves usually results in fibrinoid
necrosis within the cusps or along the tendinous cords.
a. On top of the necrotic foci are vegetations (Verrucae) which puts RHD in
the category of vegetative valve disease.
4. Subendocardial lesions, maybe from regurgitant jets, may induce thickenings
called MacCallum Plaques, usually in the left atrium.
5. Cardinal Anatomic Changes in chronic RHD
a. Leaflet Thickening
b. Commisural Fusion and Shortening
c. Thickening and Fusion of the tendinous cords
6. The left ventricle is largely unaffected by isolated pure mitral stenosis.
v.
Pathology
1. Acute rheumatic fever results from immune responses to group A streptococci,
which happen to cross-react with host tissues.
a. Antibodies directed toward M proteins of streptococci also react with self
antigens in the heart.
vi.
Clinical Features
1. RF has fiver major manifestations
a. Migratory polyarthritis of the large joints
b. Pancarditis
c. Subcutaneous nodules
d. Erythema marginatum of the skin
e. Sydenham chorea: neurologic disorder with involuntary rapid, purposeless
movements.
2. So two of the above, plus preceding group A streptococcal infection and two
minor manifestations (fever, arthralgia, or elevated blood levels of acute-phase
reactants) are need for RF diagnosis.
3. Predominant findings are carditis and arthritis, the latter more common in
adults.
a. Related to acute carditis are pericardial friction rubs, weak heart sounds,
tachycardia, and arrhythmias.
4. After the first attack there is increased vulnerability to reactivation of the same
disease and symptoms.
k. Infective Endocarditis
i.
Colonization or invasion of heart valves or mural endocardium by a microbe.
1. Leads to formation of vegetations.
2. Most cases caused by bacterial infections.
ii.
Acute IE typically caused by infection of a normal heart by a highly virulent organism
that produces necrotizing, ulcerative, destructive lesions.
1. Difficult to cure with antibiotics and usually requires surgery.
iii.
Subacute IE, the organisms are of lower virulence.
iv.
Etiology and Pathogenesis
1. RH was the major antecedent disorder, but more common now are MVP,
degenerative calcific stenosis, bicuspid aortic valve, artificial (prosthetic) valves,
and congenital defects (repaired and unrepaired).
2. Endocarditis of previously damaged valves is caused most commonly (50-60%)
by Streptococcus Viridans, which is part of the normal flora of the oral cavity.
3. Morphology
a. Hallmark of IE is friable, bulky, potentially destructive vegetations
containing fibrin, inflammatory cells, and bacteria or other organisms on
the heart valves.
b. Aorta and Mitral valves are most common sites of infection.
c. Emboli may be shed from vegetations at any time.
i.
Fragments may be virulent and can cause septic infarcts.
d. Vegetations of subacute endocarditis are linked to less valvular
destruction than those of acute endocarditis.
4. Clinical Features
a. Fever is most consistent sign of IE.
l. Noninfected vegetations
i.
Caused by nonbacterial thrombotic endocarditis and the endocarditis of Lupus.
ii.
Nonbacterial Thrombotic Endocarditis (NBTE)
1. Deposition of small sterile thrombi on the leaflets of cardiac valves.
2. Vegetations are not invasive and do not elicit any inflammatory reaction.
3. May be the source of systemic emboli that produce infarcts in the brain, heart,
etc.
4. Often happens in debilitated patients and therefore happens often with DVT,
pulmonary emboli, and other findings in hypercoagulation.
5. Endocardial Trauma, from a catheter, is another well-recognized predisposing
condition.
a. Right sided valvular and endocardial thrombotic lesions frequently track
along the course of Swan-Ganz pulmonary artery catheters.
iii.
Endocarditis of Systemic Lupus Erythematosus (Libman-Sacks Disease)
1. Small, sterile vegetations are occasionally found in SLE, are sterile, pink and
warty in appearance.
a. Consist of finely granular, fibrinous eosinophilic material that may have
hematoxylin bodies.
2. Intense valvulitis may be present, seen by fibrinoid necrosis of valve substance
contiguous with vegetation.
m. Carcinoid Heart Disease (Tyler, maybe you should read this section. I can't seem to
understand it)
i.
Cardiac manifestation of the systemic syndrome caused by carcinoid tumors.
1. Generally involves endocardium and valves of right heart.
2. Lesions present in one half of patients with symptoms of episodic skin flushing,
cramps, nausea, vomiting, and diarrhea.
ii.
Morphology
1. Lesions consist of firm plaquelike endocardial fibrous thickenings on inside
surfaces of cardiac chambers and tricuspid/pulmonary valves.
a. Thickenings made of smooth muscle cells and sparse collagen mixed with
acid muopolysaccharide-rich matrix.
iii.
Linked to elaboration of tumors by several products like serotonin, kallikrein,
bradykinin, histamine, prostaglandins, and tachykinins.
iv.
Gastrointestinal carcinoids do not usually spread to become carcinoid heart disease.
v.
Carcinoid tumors that drain directly into the inferior vena cava can induce Carcinoid
Heart Disease
vi.
Most common manifestation is tricuspid insufficiency, followed by pulmonary valve
insufficiency.
n. Complications of Artificial Valves
i.
Types
1. Mechanical Prostheses: consisting of different kinds of valves like caged balls,
tilting disks, or hinged semicircular flaps
2. Tissue Valves: chemically treated animal tissue, especially porcine aortic valve
tissue
ii.
Complications
1. Thromboembolic: local obstruction of prosthesis by thrombus or distant
thromboemboli which makes necessary long-term anticoagulation.
2. Infective Endocarditis: vegestations are usually found at the prosthesis-tissue
interface.
a. Cause formation of a ring abscess which eventually allows regurgitant
blood leak
b. Organisms causing this are staphylococcal skin contaminants, S.aureus,
streptococci, and fungi.
3. Structural Deterioration due to calcification or tearing
4. Other
a. Hemolysis due to high shear forces
b. Paravalvular leak due to inadequate healing
c. Obstruction due to overgrowth of fibrous tissue during the healing
process