Cardiovascular system pathology

1. Cardiovascular
System
Pathology
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2. Ischemic Heart Disease
Cardiac ischemia is usually secondary to coronary artery disease (CAD);
ISCHEMIC HEART DISEASE
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3. Cardiac ischemia is usually secondary to coronary artery disease (CAD); it is themost
common cause of death in the United States. It is most often seen in middle-age
men and postmenopausal women.
Angina pectoris is due to transient cardiac ischemia without cell death resulting
insubsternal chest pain.
• Stable angina (most common type) is caused by coronary artery atheroscle-
rosis with luminal narrowing >75%. Chest pain is brought on by increased cardiac
demand (exertional or emotional), and is relieved by rest or nitroglyc-erin
(vasodilation). Electrocardiogram shows ST segment depression (suben-docardial
ischemia).
• Prinzmetal variant angina is caused by coronary artery vasospasm and produces
episodic chest pain often at rest; it is relieved by nitroglycerin (vasodilatation).
Electrocardiogram shows transient ST segment elevation (transmural ischemia).
• Unstable or crescendo angina is caused by formation of a nonocclusive throm-
bus in an area of coronary atherosclerosis, and is characterized by increasing
frequency, intensity, and duration of episodes; episodes typically occur at rest. This
form of angina has a high risk for myocardial infarction.
Myocardial infarction (MI) occurs when a localized area of cardiac muscle
undergoescoagulative necrosis due to ischemia. It is the most common cause of
death in the United States. The mechanism leading to infarction is coronary artery
atheroscle-rosis (90% of cases). Other causesinclude decreased circulatory volume,
decreased oxygenation, decreased oxygen-carrying capacity, or increased cardiac
workload, due to systemic hypertension, for instance.
• Distribution of coronary artery thrombosis.The left anterior descendingartery
(LAD) is involved in 45% of cases; the right coronary artery (RCA) is involved in 35%
of cases; and the left circumflex coronary artery (LCA) is involved in 15% of cases.
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4. Infarctions are classified as transmural, subendocardial, or microscopic.
• Transmural infarction (most common type) is considered to have
occurredwhen ischemic necrosis involves >50% of myocardial wall. It is associated
with regional vascular occlusion by thrombus. It causes ST elevated MIs (STEMIs)
due to atherosclerosis and acute thromobosis.
• Subendocardial infarction is considered to have occurred when
ischemicnecrosis involves <50% of myocardial wall. It is associated with hypoperfu-
sion due to shock. ECG changes are not noted. This type of infarction occurs in a
setting of coronary artery disease with a decrease in oxygen delivery or an increase
in demand.
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5. • Microscopic infarction is caused by small vessel occlusion due to
vasculitis,emboli, or spasm. ECG changes are not noted.
The clinical presentation of MI is classically a sudden onset of severe “crushing”
substernal chest pain that radiates to the left arm, jaw, and neck. The pain may be
accompanied by chest heaviness, tightness, and shortness of breath; diaphoresis,
nausea, and vomiting; jugular venous distension (JVD); anxiety and often “feeling
of impending doom.” Electrocardiogram initially shows ST segment elevation. Q
waves representing myocardial coagulative necrosis develop in 24–48 hours.
• Gross and microscopic sequence of changes.The microscopic and
grosschanges represent a spectrum that is preceded by biochemical changes going
from aerobic metabolism to anaerobic metabolism within minutes. The time
intervals are variable and depend on the size of the infarct, as well as other factors.
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6. Complications of MI include cardiac arrhythmias that may lead to sudden car-diac
death; congestive heart failure; cardiogenic shock (>40–50% myocardium is
necrotic); mural thrombus and thromboembolism; fibrinous pericarditis; ventricu-
lar aneurysm; and cardiac rupture. Cardiac rupture most commonly occurs 3–7
days after MI, and has effects that vary with the site of rupture: ventricular free
wall rupture causes cardiac tamponade; interventricular septum rupture causes
left to right shunt; and papillary muscle rupture causes mitral insufficiency.
Sudden cardiac death is defined to be death within 1 hour of the onset of symp-toms.
The mechanism is typically a fatal cardiac arrhythmia (usually ventricular
fibrillation).
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7. Coronary artery disease is the most common underlying cause (80%); other causes
include hypertrophic cardiomyopathy, mitral valve prolapse, aortic valve stenosis,
congenital heart abnormalities, and myocarditis.
Chronic ischemic heart disease is the insidious onset of progressive congestive
heartfailure. It is characterized by left ventricular dilation due to accumulated
ischemic myocardial damage (replacement fibrosis) and functional loss of
hypertrophied non-infarcted cardiac myocytes.
CONGESTIVE HEART FAILURE
Congestive heart failure (CHF) refers to the presence of insufficient cardiac outputto
meet the metabolic demand of the body’s tissues and organs. It is the final com-
mon pathway for many cardiac diseases and has an increasing incidence in the
United States. Complications include both forward failure (decreased organ per-
fusion) and backward failure (passive congestion of organs). Right- and left-sided
heart failure often occur together.
• Left heart failure can be caused by ischemic heart disease, systemic hyperten-
sion, myocardial diseases, and aortic or mitral valve disease. The heart has
increased heart weight and shows left ventricular hypertrophy and dilatation. The
lungs are heavy and edematous. Left heart failure presents with dyspnea,
orthopnea, paroxysmal nocturnal dyspnea, rales, and S3 gallop.
Microscopically, the heart shows cardiac myocyte hypertrophy with “enlarged
pleiotropic nuclei,” while the lung shows pulmonary capillary congestion and
alveolar edema with intra-alveolar hemosiderin-laden macrophages (“heart failure
cells”). Complications include passive pulmonary congestion and edema, activation
of the renin-angiotensin-aldosterone system leading to secondary
hyperaldosteronism, and cardiogenic shock.
• Right heart failure is most commonly caused by left-sided heart failure,
withother causes including pulmonary or tricuspid valve disease and cor pulmo-
nale. Right heart failure presents with JVD, hepatosplenomegaly,
dependentedema, ascites, weight gain, and pleural and pericardial effusions.
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8. Grossly, right ventricular hypertrophy and dilatation develop. Chronic passive
conges-tion of the liver may develop and may progress to cardiac sclerosis/cirrhosis
(only with long-standing congestion).
VALVULAR HEART DISEASE
Degenerative calcific aortic valve stenosis is a common valvular abnormality char-
acterized by age -related dystrophic calcification, degeneration, and stenosis of the
aortic valve. It is common in congenital bicuspid aortic valves. It can lead to concen-
tric left ventricular hypertrophy (LVH) and congestive heart failure with increased
risk of sudden death. The calcifications are on the outflow side of the cusps. Treat-
ment is aortic valve replacement.
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9. Mitral valve prolapse has enlarged, floppy mitral valve leaflets that prolapse intothe
left atrium and microscopically show myxomatous degeneration. The condi-tion
affects individuals with Marfan syndrome. Patients are asymptomatic and a mid-
systolic click can be heard on auscultation. Complications include infectious
endocarditis and septic emboli, rupture of chordae tendineae with resulting mitral
insufficiency, and rarely sudden death.
Rheumatic valvular heart disease/acute rheumatic fever
Rheumatic fever is a systemic recurrent inflammatory disease, triggered by a pha-
ryngeal infection with Group A β-hemolytic streptococci. In genetically susceptible
individuals, the infection results in production of antibodies that cross-react with
cardiac antigens (type II hypersensitivity reaction). Rheumatic fever affects children
(ages 5–15 years), and there is a decreasing incidence in the United States.
Symptoms occur 2–3 weeks after a pharyngeal infection; laboratory studies show
elevated anti-streptolysin O (ASO) titers. The Jones criteria are illustrated below.
Diagnosis of rheumatic fever requires 2 major OR 1 major and 2 minor
criteria, plus a preceding group A strep infection.
• Acute rheumatic heart disease affects myocardium, endocardium, and peri-
cardium. The myocardium can develop myocarditis, whose most distinctive feature
is the Aschoff body, in which fibrinoid necrosis is surrounded by macrophages
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10. (Anitschkow cells), lymphocytes, and plasma cells. Fibrinous pericarditis may be
present. Endocarditis may be a prominent feature that typically involves mitral and
aortic valves (forming fibrin vegetations along the lines of closure) and may also
cause left atrial endocardial thickening (MacCallum plaques).
• Chronic rheumatic heart disease is characterized by mitral and aortic
valvularfibrosis, characterized by valve thickening and calcification; fusion of the
valve commissures; and damaged chordae tendineae (short, thickened, and fused).
Complications can include mitral stenosis and/or regurgitation, aortic steno-sis
and/or regurgitation, congestive heart failure, and infective endocarditis.
Infectious bacterial endocarditis refers to bacterial infection of the cardiac
valves,characterized by vegetations on the valve leaflets. Risk factors include
rheumatic heart disease, mitral valve prolapse, bicuspid aortic valve, degenerative
calcific aor-tic stenosis, congenital heart disease, artificial valves, indwelling
catheters, dental procedures, immunosuppression, and intravenous drug use.
• Acute endocarditis is typically due to ahigh virulence organismthat can colo-nize
a normal valve, such as Staphylococcus aureus. Acute endocarditis pro-duces large
destructive vegetations (fibrin, platelets, bacteria, and neutrophils). The prognosis
is poor, with mortality of 10–40%.
• Subacute endocarditis is typically due to a low virulence organism, such
asStreptococcus group viridians, which usually colonizes a previously
damagedvalve. The disease course is typically indolent with <10% mortality.
Clinically, endocarditis presents with fever, chills, weight loss, and cardiac murmur.
Embolic phenomena may occur, and may affect systemic organs; retina (Roth
spots); and distal extremities (Osler nodes [painful, red subcutaneous nodules on
the fin-gers and toes], Janeway lesions [painless, red lesions on the palms and
soles], and splinter fingernail hemorrhages). Diagnosis is by serial blood cultures.
Complica-tions include septic emboli, valve damage resulting in insufficiency and
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11. congestive heart failure, myocardial abscess, and dehiscence of an artificial heart
valve.
Marantic endocarditis (nonbacterial thrombotic endocarditis [NBTE]) is character-
ized by small, sterile vegetations along the valve leaflet line of closure in patients
with a debilitating disease. The major complications are embolism and secondary
infection of the vegetations.
MYOCARDITIS
Myocarditis is caused by infectious (coxsackie A and B viruses, Chagas disease)
andimmune causes. Clinically, the patient may be asymptomatic or may suffer from
acute heart failure or even dilated cardiomyopathy.
CONGENITAL HEART DISEASE
Congenital heart disease is the most common cause of childhood heart disease inthe
United States; 90% of cases are idiopathic and 5% are associated with genetic
disease (trisomies, cri du chat, Turner syndrome, etc.), viral infection (especially
congenital rubella), or drugs and alcohol.
Coarctation of the aorta is a segmental narrowing of the aorta.
• Preductal coarctation (infantile-type) is associated with Turner syndrome
andcauses severe narrowing of aorta proximal to the ductus arteriosus. It is usu-
ally associated with a patent ductus arteriosus (PDA), which supplies blood to aorta
distal to the narrowing, and right ventricular hypertrophy (secondary to the need
for the right ventricle to supply the aorta through the patent ductus arteriosus). It
presents in infancy with congestive heart failure that is accom-panied by weak
pulses and cyanosis in the lower extremities; the prognosis is poor without surgical
correction.
• Postductal coarctation (adult-type) causes stricture or narrowing of the
aortadistal to the ductus arteriosus. It can present in a child or an adult with hyper-
tension in the upper extremities, and hypotension and weak pulses in the lower
extremities. Some collateral circulation may be supplied via the internal mammary
and intercostal arteries; the effects of this collateral circulation may be visible on
chest x-ray with notching of the ribs due to bone remodeling as a consequence of
increased blood flow through the intercostal arteries.
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12. Complications can include congestive heart failure (the heart is trying too hard),
intracerebral hemorrhage (the blood pressure in the carotid arteries is too high),
and dissecting aortic aneurysm (the blood pressure in the aortic route is too high).
Tetralogy of Fallot is the most common cause of congenital cyanotic heart
disease.The classic tetrad includes right ventricular outflow obstruction/stenosis;
rightventricular hypertrophy; ventricular septal defect; and overriding aorta.
Clinicalfindings include cyanosis, shortness of breath, digital clubbing, and
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13. polycythemia. Progressive pulmonary outflow stenosis and cyanosis develop over
time; treatment is surgical correction.
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14. Transposition of the great vessels is an abnormal development of the
truncoconalseptum whereby the aorta arises from the right ventricle, and the
pulmonary artery arises from the left ventricle. The risk is increased in infants of
diabetic mothers. Affected babies develop early cyanosis and right ventricular
hypertrophy. To survive, infants must have mixing of blood by a VSD, ASD, or PDA.
The prognosis is poor without surgery.
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15. Truncus arteriosus is a failure to develop a dividing septum between the aorta
andpulmonary artery, resulting in a common trunk. Blood flows from the
pulmonary trunk to the aorta. Truncus arteriosus causes early cyanosis and
congestive heart failure, with a poor prognosis without surgery.
Tricuspid atresia refers to the absence of a communication between the right
atriumand ventricle due to developmental failure to form the tricuspid valve.
Associated defects include right ventricular hypoplasia and an ASD. The prognosis
is poor without surgery.
Ventricular septal defect (VSD), which consists of a direct communication betweenthe
ventricular chambers, is the second most common congenital heart defect (the
most common is a bicuspid aortic valve).
• A small ventricular septal defect may be asymptomatic and close sponta-
neously, or it may produce a jet stream that damages the endocardium and
increases the risk of infective endocarditis.
• A large ventricular septal defect may cause Eisenmenger complex, which is
characterized by secondary pulmonary hypertension, right ventricular hyper-
trophy, reversal of the shunt, and late cyanosis.
• In both types, a systolic murmur can be heard on auscultation. Ventricular
septal defects are commonly associated with other heart defects. Large ven-tricular
septal defects can be surgically corrected.
Atrial septal defect (ASD) is a direct communication between the atrial chambers.
The most common type is an ostium secundum defect. Complications include
Eisenmenger syndrome and paradoxical emboli.
Patent ductus arteriosus (PDA) is a direct communication between the aorta
andpulmonary artery due to the continued patency of the ductus arteriosus after
birth. It is associated with prematurity and congenital rubella infections. Clinical
findings include machinery murmur, late cyanosis, and congestive heart failure.
Eisenmenger syndrome may develop as a complication.
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16. PRIMARY CARDIOMYOPATHIES (DIAGNOSIS OF
EXCLUSION)
Dilated cardiomyopathy (most common form) is cardiac enlargement with
dilatationof all 4 chambers, resulting in progressive congestive heart failure (typical
mode of presentation). The cause is genetic in 20–50% of cases, but some cases are
related to alcohol, medications (Adriamycin [doxorubicin]), cocaine, viral
myocarditis (Cox-sackievirus B and enteroviruses), parasitic infections (Chagas
disease), iron overload or pregnancy.
In cases of all types, the underlying etiology leads to destruction of myocardial con-
tractility, which affects systolic function. Echocardiogram typically shows
decreased ejection fraction. Complications include mural thrombi and cardiac
arrhythmias; prognosis is poor with 5-year survival of 25%. Treatment is heart
transplantation. There is myocyte hypertrophy with interstitial fibrosis on
microscopy, and eccentric hypertrophy seen on gross examination.
Hypertrophic cardiomyopathy (also called asymmetrical septal hypertrophy,
andidiopathic hypertrophic subaortic stenosis [IHSS]) is a common cause of sudden
cardiac death in young athletes. The condition is an asymmetrical hypertrophy of
cardiac muscle that causes decreased compliance affecting diastolic function.
Hypertrophic cardiomyopathy can be an autosomal dominant disorder (>50% of
cases) or idiopathic. The muscle hypertrophy is due to the increased synthesis of
actin and myosin, and on microscopic examination, the cardiac muscle fibers are
hypertrophied and in disarray. Hypertrophic cardiomyopathy is most prominent in
the ventricular septum, where it can obstruct the ventricular outflow tract. This can
potentially lead to death during severe exercise when the cardiac outflow tract
collapses, preventing blood from exiting the heart.
Restrictive cardiomyopathy (uncommon form) is caused by diseases which
producerestriction of cardiac filling during diastole; etiologies include amyloidosis,
sarcoid-osis, endomyocardial fibroelastosis, and Loeffler endomyocarditis. In all of
these diseases, increased deposition of material leads to decreased compliance,
affecting diastolic function. On gross examination, the ventricles are not enlarged
and the cavities are not dilated. Microscopy will reflect the underlying cause.
Arrhythmogenic right ventricular cardiomyopathy causes thinning of the right ven-
tricle due to autosomal dominant mutations that encode desmosomal junctional
proteins. On microscopy, there is fatty infiltration of the myocardium.
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17. CARCINOID HEART DISEASE
Carcinoid heart disease is right-sided endocardial and valvular fibrosis secondaryto
serotonin exposure in patients with carcinoid tumors that have metastasized to the
liver. It is a plaque-like thickening (endocardial fibrosis) of the endocardium and
valves of the right side of the heart. Many patients experience carcinoid syndrome
(also related to secretion of serotonin and other metabolically active products of
the tumors), characterized by skin flushing, diarrhea, cramping, bronchospasm,
wheezing, and telangiectasias. The diagnosis can be established by demonstrating
elevated urinary 5-hydroxyindoleacetic acid (5-HIAA), a metabolite of the break-
down of serotonin via monoamine oxidase
CARDIAC TUMORS
Primary cardiac tumors are rare. The majority are benign; the malignant tumors are
sarcomas. Treatment is excision.
• Cardiac myxoma is a benign tumor usually arising within the left atrium nearthe
fossa ovalis in decades 3-6 of life; it can present like mitral valve disease. In 10% of
cases there is an autosomal dominant condition known as Carney complex
(myxomas with endocrine abnormalities and lentigines or pigmented nevi). Cardiac
myxoma is characterized microscopically by stellate-shaped cells within a myxoid
background. Complications include tumor emboli and “ball-valve” obstruction of
the valves.
• Cardiac rhabdomyoma is a benign tumor usually arising within the myocardium
that is associated with tuberous sclerosis.
PERICARDIAL DISEASE
Pericarditis.There are 2 kinds of pericarditis, acute and chronic.
• Acute pericarditis is characterized by a fibrinous exudate (viral infection
oruremia) or by a fibrinopurulent exudate (bacterial infection).
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18. • Chronic pericarditis can occur when acute pericarditis does not resolve
andadhesions form.
Pericardial effusion may be serous (secondary to heart failure or
hypoalbuminemia),serosanguineous (due to trauma, malignancy, or rupture of the
heart or aorta) or chylous (due to thoracic duct obstruction or injury).
Tumors of the lung and breast may spread by direct extension to the pericardia.
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