Endocarditis, Infective

KEY FEATURES

ESSENTIALS OF DIAGNOSIS

• Clinical features: fever, new valvular regurgitation, embolization, immune complexes, predisposing condition.

• ≥ Two positive blood cultures with a typical microbe

• Characteristic cardiac lesions on echocardiography or histology

GENERAL CONSIDERATIONS

• Infective endocarditis represents an endothelial infection that usually occurs at sites of endothelial damage in blood vessels and is rare

• Infection of cardiac valve endocardium is not rare and can afflict normal valves, but preexisting valve disease as a substrate is more common.

• Valve infection probably begins with minor trauma, which would explain the observation that the valves with the highest force necessary to close the valve are the most commonly affected; in rank order: mitral, aortic, tricuspid, pulmonic. Also, infection usually starts at the closure line of the valves

• Minor trauma may form a microscopic thrombus on the leaflet surface, which forms the nidus for infection

• For the nidus to become infected, bacteria must enter the bloodstream in sufficient numbers from a break in the epidermal or mucosal surfaces of the body

• As the vegetation grows, regurgitation of the affected valve almost always occurs due to destruction, scarring, or retraction of the leaflet

• Occasionally, chordal involvement results in rupture or erosion of the leaflet to perforation, both of which can cause sudden severe atrioventricular valve regurgitation

• Very large vegetations rarely can obstruct the valve orifice

• Embolization of vegetations can result in damage to other organs from ischemia or remote infection

• Invasion of the valve annulus by the organisms can lead to abscesses and fistulas

• Infection of arterial walls due to vegetation embolization can lead to aneurysm formation and rupture, which can be devastating in the central nervous system

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

• Common symptoms: fever, chills, weakness, dyspnea

• Less common symptoms: diaphoresis, weight loss, cough, stroke, rash, nausea/vomiting, headache, chest pain, myalgias/arthralgias

• Unusual symptoms: abdominal pain, delirium/coma, hemoptysis, back pain

PHYSICAL EXAM FINDINGS

• Common findings: fever, heart murmur, skin lesions or emboli, petechiae

• Less common findings: Osler’s node, Janeway lesion, splinter hemorrhages, splenomegaly, stroke, heart failure, pneumonia, meningitis

• Unusual findings: new or changing murmur, retinal lesions (Roth spots), renal failure, blue toe syndrome

• Splenomegaly

DIFFERENTIAL DIAGNOSIS

• Fever due to other causes

• Sepsis not due to infective endocarditis

• Valvular lesions on echocardiography that resemble infective vegetations: myxomatous valves, Libman-Sacks vegetations, marantic vegetations, papillary fibroelastomas, Lambl excrescences, nodules of Arantius (aortic valve)

DIAGNOSTIC EVALUATION

LABORATORY TESTS

• Blood cultures: 3 from separate venipunctures over 24 hours

• Serologic testing for organisms such as Histoplasma, Q fever, Brucella, Bartonella

• Rheumatoid factor may be falsely positive

• Leukocytosis, elevated gamma globulins, elevated erythrocyte sedimentation rate, anemia

ELECTROCARDIOGRAPHY

• Sinus tachycardia

• Aortic valve abscess formation can lead to first-, second-, ...