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Chapter: Pathology: Cardiac Pathology

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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.

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.

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 (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 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.




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