Editorial [Hot topic: Infective Endocarditis (Guest Editor: Ioannis Starakis)]

The diagnosis of IE is frequently supported by an assemblage of clinical findings rather than a sole definitive test result. The diagnosis usually becomes apparent when there are several positive blood cultures in the occurrence of a documented underlying cardiac defect. Nevertheless, some IE patients do not have positive blood cultures and approximately 25 to 30 % of patients have no recognizable underlying cardiac lesions at the onset of the disease. Keeping that in mind along with the fact that the disease may be present with atypical features, the physicians may avoid unnecessary delays in establishing a diagnosis and promptly introduce the appropriate treatment modalities. The overall incidence of infective endocarditis is 1.7 to 4.0 per 100,000 population and in adults older than 50 years, it exceeds 15 per 100,000 population. However, the precise incidence of IE is difficult to be determined because case definitions have diverged from decade to decade, among different authors, and among different medical facilities. Furthermore, the incidence of predisposing conditions (e.g., rheumatic heart disease and injection drug use) has wandered over time and among different areas. Sex and age have an impact on the incidence of IE with men prevailing in most series, and almost 50-60% of cases of acute IE do not necessitate an underlying heart condition to be present. The microorganisms most accountable for the development of acute IE (e.g. S. aureus) are exceedingly virulent and able to colonize normal heart valves. Nowadays, the incidence of acute IE has been progressively increasing and surpasses the number of subacute IE cases. Elderly patients or those with congenital heart defects, rheumatic heart disease, immunosuppression, AIDS, intravenous drug abuse (IVDA) and patients with a malignancy are more vulnerable to IE. Mitral valve prolapse comprises the most common (30%) predisposing condition found in young adults, and bicuspid aortic valve is the most common underlying congenital condition (15%). Rheumatic heart disease currently accounts for less than 20% of cases, but 6% of these patients develop IE in their lifetimes. In 75% of cases of IVDA IE, no underlying valvular abnormalities are noted, and 50% of them involve the tricuspid valve. Prosthetic valve endocarditis (PVE) accounts for 10-20% of all cases of IE, and in the long run, 5% of mechanical and bioprosthetic valves become infected. Mechanical valves are more likely to be infected within the first 3 months of implantation, and bioprosthetic valves are more likely to be infected after the first year. The mitral valves are more vulnerable than those in the aortic area. Analogous to PVE are infections of implantable pacemakers (PMs) and cardioverter -defibrillators. Usually, these devices are infected within a few months of implantation. The principle causative agents include Streptococcus viridans (55%), Staphylococcus aureus (30%), Enterococcus (6%) and HACEK bacteria, although on occasions it can also be caused by fungi. Earlier than the accessibility of antimicrobial regimens, IE was consistently lethal. Nowadays, roughly 80 % of IE patients will survive from this infection, but in the same time one out of every six IE patients will succumb during their initial hospitalization, and when highly virulent agents (such as S. aureus) are implicated almost 30% of these patients may not survive as a direct or indirect result of their valvular infection. It should also be noted that an unfavourable outcome in these patients may arise regardless of the timely institution of the appropriate antimicrobial treatment and in spite of the dexterous implementation of contemporary diagnostic procedures. Antibiotics are usually administered intravenously for 2-6 weeks and duration usually depends on the pathogen's virulence. Fifteen to twentyfive percent of IE patients are treated surgically. Surgery was not introduced in the management of IE until 1961, but during the last decades, valve replacement or repair have become everyday practice when confronting with certain complications of IE. Moreover, the decline in mortality from IE has been attributed to the amalgamation of appropriate antibiotic treatment and judicious surgical approach. The removal of an infected valve is necessary when antibiotic therapy fails, there are persistent vegetations after systemic embolization or vegetations increase their size after antimicrobial treatment, in valvular dysfunction and in fungal endocarditis. Complications, including metastatic abscesses, are common. The mortality rate of IE is 25%. The risk of death increases with the occurrence of complications, and mortality rates as high as 40% are observed with S. aureus infective endocarditis. Even though there are no prospective randomized trials which have proven that prophylactic antibiotic administration for preventing bacterial endocarditis is beneficial, this approach has become standard in most developed countries. To our opinion, it is rather improbable that such a trial will ever be carried out, known the exceptionally low incidence of IE following procedures such as dental surgery and also the medical ethics and legal environment in the United States and Europe. In the present mini hot topic the authors have focused on the current prevention guidelines, the major issues related to the antimicrobial therapy and the effectiveness, indications for, and outcomes of surgery in IE. The clinical characteristics and management of IE, including aspects of IE that are distinctive to or typical of patients, who are injecting illicit substances, will also be reviewed here. Finally, there a special review article concerning Q fever endocarditis which represents the most severe and frequently lethal appearance of chronic Q fever.