**3. Conclusions**

with native valve IE older than 60 years [103]. Calcified mitral annulus is a common finding in elderly women but rarely complicate with IE (3.8%) [104]. Even not a classical condition related to IE, idiopathic hypertrophic subaortic stenosis may represent up to 5% of incidence of the infection [105]. And there is a higher mortality rate correlation if a murmur is present (up to 36% of patients with hypertrophic aortic stenosis and IE) [105]. Another condition associated with IE is the mitral prolapse syndrome. In different series, the range of IE in those patients with mitral valve prolapse can go from 11 to 23% [106, 107]. In another study, 8.6% of patients with mitral valve prolapse who were monitored prospectively for 9–22 years developed IE [108]. This syndrome must be suspected in patients with mid-systolic click with or without a late systolic murmur. This condition is not uncommon and has been found in 0.5– 20% of otherwise healthy people, especially young women. It has become apparent that a significant proportion of patients with mitral valve prolapse have an anthropometrically distinct habitus, suggesting that this condition is only an element of a generalized developmental syndrome [109]. It may be useful to have in mind these characteristics to help identify patients with a high risk of developing IE. Having valvular redundancy and thickened leaflets may increase the risk of IE [103]. The combination of mitral valve prolapse and men older than 45 years also may increase the risk of IE [110]. In a detailed case-control study, 25% of patients with IE had mitral valve prolapse; the odds ratio (8.2 of 95% confidence interval, 2.4–28.4) indicated a substantially higher risk for IE in patients with mitral valve prolapse than for those without it [111]. Another study found that mitral valve prolapse IE presented with more subtle symptoms, less mortality, and responded better to antimicrobial therapy than other types of

left-sided IE, even though recognition of the infection was delayed [112].

All estimations of IE incidence in drug abusers are hindered because there are no enough data reporting the exact number of victims of illicit drug-abuse epidemic. Reports from the United States present an incidence of IE in intravenous drug abusers that range from 2 to 5% per year [113] or 1.5–2 cases per 1000 years of IV drug abuse with men more commonly affected [114]. Although congenital cardiac disease and right-sided heart instrumentation are associated with IE, IV drug abusers retain the majority of cases. Intravenous drug users and those with HIV primarily consist of relatively young adults [115]. Acute infection accounts for approximately 60% of hospital admissions among drug abusers and IE is responsible of 5–15% of these episodes [116]. The presence of IE in a drug addict is difficult to predict, especially from history and physical examination findings alone [117, 118]. More than 60% of IV drug abusers with IE do not have an underlying preexisting valvular disease [119]. Although cocaine use by an intravenous drug abuser should raise the suspicion of IE infection [120], the most credible predictors of IE in febrile intravenous drug users are visualization of vegetations by echocardiography and the presence of embolic phenomena [118]. Up to 13% of cases of IV drug abusers with febrile episodes have an echocardiographically demonstrated IE [118]. Although leftsided native valve endocarditis may be present in this group of patients, the tricuspid valve is more commonly affected in intravenous drug users [121, 122]. Only two-third of patients with proven IE diagnostic presented with heart murmurs on admission [116]. The frequency of valvular involvement is tricuspid alone or in combination with other valves, 52.2%; aortic

**2.9. Infective endocarditis in drug abusers**

44 Contemporary Challenges in Endocarditis

Much work remains to be completed. IE is a complex and challenging pathology with a high mortality rate despite current advancements in health care. Even though diagnostic and therapeutic modalities have progressed since the "rheumatic fever" era, there is still a concern in developing countries where rheumatic fever represents a major cause of IE and access to appropriate health care is not possible in large areas. Curiously, the changing epidemiology of IE depict us a disease that used to affect young patients, native valves, and had *Streptococci* as the main pathogen, to a disease that affect mainly older people with prosthetic valves implanted and *S. aureus* as the main pathogen. These changes occur alongside a better survival in older people but also with several comorbidities accompanying these patients. Imaging modalities such as echocardiography had greatly helped in the diagnosis of IE; the role of advanced imaging had yet to be clinically evaluated in a day-to-day basis. Chronic and immunosuppressive diseases play a major role as predisposing factors to develop IE. IV drug users comprise other group of patients severely affected by the disease. Adequate clinical analysis and high suspicion are necessary to help these "risk" patients and provide the right tools (multidisciplinary team) to detect and treat this limiting and deadly condition.
