Aortic Valve Endocarditis
Endocarditis is an infectious disease process of the endocardial surface of the heart and valves that is more common in the United States than previously believed and is steadily increasing. The risk of infection dramatically increases with congenital heart disease, history of rheumatic fever or existing valvular damage, major dental treatment, open heart surgery, and genitourinary procedures; however, the use of intravenous drugs has become a massive public health burden in terms of acquiring endocarditis. Between 2002 and 2014, the Centers for Disease Control and Prevention estimated a near quadrupling of heroin-related overdose deaths. Although overdose contributes most to drug-associated mortality, the major morbidity related to intravenous drug use is the infectious manifestations leading to protracted hospitalizations rife with large operations and costly treatments. Further supporting this data, the incidence of hospital discharge diagnoses for drug dependence combined with endocarditis, as provided from the North Carolina Hospital Discharge Database between 2010 and 2015, increased from 0.2 to 2.7 per 100,000 persons per year. Hospital costs for these patients increased 18-fold, from $1.1 million in 2010 to $22.2 million in 2015.
Depending on the route of infection the infectious vector can be highly variable. The recent literature has identified the incidence of Staphylococcus aureus has dramatically increased and has now become the most common causative organism in most of the industrialized world. In up to 24% of cases, no organisms can be cultured. Murdoch and colleagues organized a prospective cohort study with the International Collaboration on Endocarditis in which they identified 2781 patients with infectious endocarditis (IE). The pathogenic distribution was 31% Staphylococcus aureus, 17% Streptococcus viridans, 11% Enterococcus, 11% Coagulase negative staphylococcus, 7% Streptococcus bovis, 5% other streptococci. The remainder pathogens were 2% or less: the group of Haemophilus species, Aggregatibacter species, Cardiobacterium hominis, Eikenella corrodens, and Kingella species (HACEK), non-HACEK gram-negative bacteria, and fungi. Fungal endocarditis is quite rare but has been recognized as a cause of early prosthetic valve endocarditis. With a survival rate of less than 20%, many consider fungal endocarditis a “stand-alone indication” for surgical replacement of an infected valve, amphotericin B is the initial drug of choice, and after completion of initial parenteral therapy, lifelong suppressive therapy with an oral azole is reasonable.
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