Endocarditis
LIFE-THREATENING DISORDERAlso called infective endocarditis and bacterial endocarditis, endocarditis is an infection of the endocardium, heart valves, or a cardiac prosthesis, resulting from bacterial or fungal invasion. This invasion produces vegetative growths on the heart valves, the endocardial lining of a heart chamber, or the endothelium
of a blood vessel that may embolize to the spleen, kidneys, central nervous system, and lungs.
of a blood vessel that may embolize to the spleen, kidneys, central nervous system, and lungs.
In endocarditis, fibrin and platelets aggregate on the valve tissue and engulf circulating bacteria or fungi that flourish and produce friable verrucous vegetations. Such vegetations may cover the valve surfaces, causing ulceration and necrosis; they may also extend to the chordae tendineae, leading to their rupture and subsequent valvular insufficiency.
Untreated endocarditis is commonly fatal, but with proper treatment, about 70% of patients recover. The prognosis is worst when endocarditis causes severe valvular damage, leading to insufficiency and heart failure, or when it involves a prosthetic valve.
Causes
Endocarditis occurs most commonly in I.V. drug abusers, patients with prosthetic heart valves, and those with mitral valve prolapse (especially males with a systolic murmur). These conditions have surpassed rheumatic heart disease as the leading risk factor.
Other predisposing conditions include coarctation of the aorta; tetralogy of Fallot; subaortic and valvular aortic stenosis; ventricular septal defects; pulmonary stenosis; Marfan syndrome; degenerative heart disease, especially calcific aortic stenosis; and, rarely, syphilitic aortic valve. Some patients with endocarditis have no underlying heart disease.
Infecting organisms
Organisms that cause infection differ among patient groups. In patients with native valve endocarditis who aren’t I.V. drug abusers, causative organisms usually include, in order of frequency, streptococci (especially Streptococcus viridans), staphylococci, and enterococci. Although many other bacteria occasionally cause the disorder, fungal causes are rare in this group. The mitral valve is involved most commonly, followed by the aortic valve.
In patients who are I.V. drug abusers, Staphylococcus aureus is the most common infecting organism. Less frequently, streptococci, enterococci, gram-negative bacilli, or fungi cause the disorder. Most often the tricuspid valve is involved, followed by the aortic valve and then the mitral valve.
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