Infective Endocarditis & Noninfected vagetation

Tahir Ramzan

Waht is Endocarditis

• Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves (native or prosthetic valves). Other structures that may be involved include the interventricular septum, the chordae tendineae,

Infective Endocarditis

• Infective endocarditis is a form of endocarditis, or inflammation, of the inner tissue of the heart (such as its valves) it is characterized by microbial invasion of heart valves or mural endocardium-often with destruction of the underlying cardiac tissues-and results in bulky, friable vegetations composed of necrotic debris, thrombus, and organisms.

• IE is classified into acute and subacute forms, mostly on the basis of clinical tempo and severity

Classification of IE

• Acute IE: -more likely due to Staphylococcus aureus- Usually suggests a destructive infection, causing death within days to weeks in more than 50% of patients despite antibiotics and surgery.

• Subacute endocarditis: is often due to streptococci of low virulence and mild to moderate illness which progresses slowly over weeks and months and has low propensity to hematogenously seed extracardiac sites

Pathogenesis

• IE can develop on previously normal valves, but the presence of cardiac abnormalities predisposes to such infections.

• Sterile platelet-fibrin deposits at sites of jet streams caused by pre-existing cardiac disease may also contribute in seeding of bacteria leading to endocarditis.

Cont…

• Host factors :such as neutropenia, immunodeficiency, malignancy, therapeutic immunosuppression, diabetes mellitus, and alcohol or intravenous drug abuse also increase the risk of IE

• Endocarditis of previously damaged or otherwise abnormal valves is caused most commonly (50% to 60% of cases) by viridans Streptococci, a relatively banal group of normal oral flora

Cont…

• More rarely, gram-negative bacilli and fungi are involved. In about 10% of cases, no organism can be isolated from the blood ("culture-negative" endocarditis). This is attributed to previous antibiotic therapy or difficulties in isolating the offending agent, or because deeply embedded organisms within the enlarging vegetation are not released into the blood.

• Foremost among the conditions predisposing to endocarditis is seeding of the blood with microbes

Clinical Features

• Fever is the most consistent sign of IE. However, in subacute disease (particularly in the elderly) fever may be absent

• The only manifestations may be nonspecific fatigue, weight loss, and a flulike syndrome. Splenomegaly is common in subacute IE.

Cont..

• Murmurs are present in 90% of patients with left-sided lesions, but these may merely relate to the pre-existing cardiac abnormality predisposing to IE.

• Diagnosis is largely made on the basis of positive blood cultures, echocardiographic findings, and other clinical and laboratory findings.

Reference: "Robins Basic Pathology"

Non-infected Vegetations:

• Nonbacterial thrombotic endocarditis (NBTE) is characterized by the deposition of variably sized masses of fibrin, platelets, and other blood components on cardiac valves.

• In contrast to IE, the valvular lesions of NBTE are sterile and do not contain microorganisms. Valvular damage is not a prerequisite for NBTE.

Pathogenesis

• It typically occurs in the setting of ..

• hypercoagulable states

• hyperestrogenic states.

• malignant cancers.particularly adenocarcinomas

• Endocardial trauma ..

Clinical Features

• The local effect on the valve is usually trivial, NBTE lesions can become clinically significant by embolizing to the brain, heart, or other organs.

• NBTE can also serve as a potential host for bacterial colonization and thus leads to development of IE

• Reference: "Robins Basic Pathology"

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