IE is a severe condition with a high risk of complications and mortality, requiring specialised multidisciplinary management. This study presented a series of 502 episodes of definite IE in adult patients, diagnosed according to the modified Duke criteria, at a federal public hospital in Rio de Janeiro. Few case series of IE have been reported from Brazilian centres [12–14] and other low- and middle-income countries. To facilitate the discussion, we compiled Tables 1–4 from the literature (Supplementary Material). Our study revealed a mean patient age of 48 years, consistent with the literature indicating that younger age groups are more commonly affected in the low- and middle-income countries [15–19]. This finding is associated with the frequent presence of rheumatic valvopathy as a predisposing factor, leading to earlier onset of IE [17; 18]. Rheumatic valvopathy was also prevalent in two other Brazilian studies from Southeastern centres [12; 13]. In contrast, a larger IE series by Murdoch et al. [2], which included 2,781 adults from 58 hospitals across 25 countries from 2000 to 2005, reported a median age of 57.9 years. The EURO-ENDO study [20], including 3,116 patients from 2016 to 2018, predominantly from European centres, reported a median age of 65 years. Recent case series from European countries have also reported higher mean ages compared to our study [21; 22]. The most common underlying cardiac conditions in this cohort were rheumatic valvopathy (30.7%) and congenital heart disease (13.9%), which is consistent with the literature. Studies from other developing countries, such as French Polynesia [23], Saudi Arabia [18], and China [17] have also highlighted these conditions as significant predispositions for IE. Rheumatic valvopathy was present in 15% of patients in Saudi Arabia [18], 33% in French Polynesia [23], and 17% in China [17] (Supplementary Table 1).
Regarding the male-to-female ratio, our study showed a male predominance, similar to studies from East Asia [18] (67%), Africa [19] (67.1%), and South America [15] (68.7%), as well as studies from developed countries [21–22; 24] (Supplementary Table 1).
Although IE was once considered a rare disease, the literature has reported a significant increase in cases over time, both in developed and developing countries. Similarly, we found an increasing trend in the number of cases over the study period. This higher incidence is likely related to an increase in high-risk populations, including older adults, individuals with multiple comorbidities, and those undergoing haemodialysis [8; 12; 20]. This trend supports CHF and chronic renal failure as prevalent comorbidities among patients who developed IE at our centre.
IE on native valves occurred in 68.5% of patients, with a higher incidence on the aortic and mitral valves, similar to observations in both developed and developing countries [2; 5; 12; 14; 17–18; 20–21; 25]. Prosthetic valve endocarditis accounted for 31.47% of cases, similar to findings in Italy [22], Saudi Arabia [18], Turkey [26], and other Brazilian studies (27.1%; 48.4%) [12–13]. Despite the predominant involvement of native valves, the incidence of prosthetic valve endocarditis has increased, consistent with the rising number of valve surgeries in recent years [28]. In low- and middle-income countries, the incidence of prosthetic valve endocarditis is significantly lower than that of native valve endocarditis, possibly due to limited access to healthcare and fewer valve replacements [17; 26]. The incidence of IE in implantable cardiac electronic devices has shown an increasing trend owing to higher device insertion rates, population aging, and increased comorbidities. In this study, it represented approximately 8% of all cases over the past 17 years, a proportion similar to that reported in Argentina, China, and Turkey [15–16; 26] (Supplementary Table 2).
The signs and symptoms of IE vary depending on the severity of the infection. The most relevant classical signs and symptoms observed were fever (90.6%) and heart murmur (50.7%), consistent with other studies (Supplementary Table 4). Classic Oslerian manifestations of endocarditis were present in only 3% of patients upon hospital admission, aligning with findings from other Brazilian [13] and Chinese [17] studies. Notably, most patients did not exhibit the classic clinical findings traditionally associated with IE. Although embolic manifestations were frequent (45%) in this cohort, other studies reported a lower proportion despite a significant number of cases [13–14; 17; 21; 29; 30]; in our study, emboli were often detected radiologically rather than clinically. This underscores the recommendation for echocardiography in cases of bacteraemia and screening for embolic events, even in asymptomatic patients [31].
In comparison with published literature from Argentina [15], China [17], and the USA [32], the vegetation rate in our study (82.9%) closely aligns with the rates reported in these studies (80.9%, 86%, and 84.1%, respectively) (Supplementary Table 2). However, the proportion of patients who underwent TEE in this cohort (78%) was significantly higher than that reported in a Chinese study (12.8%). This contrasts with the 2015 ESC guidelines on IE [1], which recommend performing TEE to exclude perivalvular complications, even if TTE shows findings compatible with IE. The high frequency of TEE in our study reflects the setting of a highly specialised surgical cardiology hospital. The lower utilisation of TEE in other studies may have led to lower detection rates of perivalvular complications such as valve perforation and perivalvular abscess, potentially resulting in diagnostic errors in patients with subtle or early valvular lesions.
The number of positive blood cultures in this study was lower than that in studies from developed countries [21; 25; 27; 29] but higher than those from developing countries [16–18], as demonstrated in Supplementary Table 3. Brazilian studies reported blood culture positivity rates of 66.5% [12], 76.9% [13], and 76.6% [14]. The low rate of microbiological detection may be related to antibiotic use before blood culture collection, as previously described by our group, where the rate of prior antibiotic use reached 75% [11]. Additionally, over half of the patients in our centre were referred from other medical institutions, where antibiotic treatment is often initiated before blood cultures are collected. Oral streptococci were the primary etiological agents used in this study. Likewise, studies from Argentina and China [15–16] show predominance of oral streptococci, in contrast to those in developed countries [25; 27], where S. aureus has become the main aetiology (Supplementary Table 3). The increase in staphylococcus infections is primarily attributed to the high incidence of infections among intravenous drug users [5; 25], patients undergoing haemodialysis [25], and older patients with comorbidities. However, the proportion of intravenous drug users and octogenarians was low in our cohort compared to developed countries [25; 27; 32]. Notably, poor oral health in patients treated by the Brazilian public health system may contribute to the prevalence of oral streptococci [11, 33].
The complications of IE are widespread and can affect multiple organs. Systemic embolization is the most frequent complication included in the Duke diagnostic criteria [28]. The sites of embolization depend on the affected valves and may involve the spleen, liver, kidneys, lungs, brain, vertebral bodies, and iliac and mesenteric arteries. Left-sided involvement commonly leads to splenic and cerebral emboli, while right-sided involvement causes pulmonary emboli [28]. Detection of these complications is often hindered by delayed diagnosis [7; 30; 31]. As shown in Supplementary Table 4, embolization was the most frequently reported complication, although not all studies specified the affected areas. All studies reviewed demonstrated a higher incidence of left-sided endocarditis than right-sided endocarditis, resulting in more splenic embolization.
Surgery is indicated to prevent progressive and irreversible structural damage and is justified in patients at high risk where cure with antibiotic therapy alone is unlikely and in those who do not have comorbidities or severe complications that make recovery prospects remote [1; 7]. This review revealed that a wide range of patients underwent surgery for IE, from 17.2% in Japan [24] to 69.7% in Turkey [26].
Studies from the USA have demonstrated surgical indication rates of approximately 25% [25, 32], which are lower than those in our cohort (Supplementary Table 4). Although the USA is a high-income country, intravenous drug abuse has increased substantially, contributing to the predisposition of individuals to IE and the acquisition of more virulent pathogens [25]. This increase has significant consequences because IE due to S. aureus infection is associated with a higher likelihood of requiring surgical treatment and worse overall outcomes. The study with the lowest surgical indication rate in this review was Japan [24] (17.2%), which despite also being a high-income country, has an older average population age (69.1 ± 14 years) with multiple comorbidities, often reducing the drive for surgical intervention.
Unfortunately, our cohort did not have sufficient power to compare patients who underwent early intervention with those who underwent late surgery. However, our study provided evidence supporting the assumption that surgically treated patients have better outcomes than conservatively managed patients. Early surgery is recommended (and reduces mortality) in cases of IE with complications such as embolic events, CHF, and valvular abscesses [1; 4; 7; 37].
Despite improvements in the diagnostic accuracy, medical therapy, and surgical techniques, IE mortality rates remain relatively high worldwide. In our study, we observed an overall hospital mortality rate of 25%, which is similar to the rates observed in Japan [24] (26.1%) and Turkey [26] (22.6%).
However, these results were lower than those of other studies, such as French Polynesia [35] (37%) and Spain [21] (34.7%). This may be due to the younger age of our patients and lower proportion of infections caused by S. aureus. Oral streptococcal species were the most frequently identified microorganisms in our study, which may have contributed to the favourable outcomes. Additionally, early surgery has been reported to improve the prognosis of IE. Thus, early surgery for IE has been increasingly performed in recent years, likely contributing to the gradual decline in IE hospital mortality rates at some centres [29].
Available studies in Brazil have reported higher mortality rates than ours (Minas Gerais, 32%; São Paulo, 33%; and Rio Grande do Sul, 41.9%) [12–14]. These higher rates may be attributed to differences in patient profiles, with a prevalence of multiple comorbidities, and differences in hospital profiles, as ours is a referral centre in cardiology with a tendency to perform early surgeries [12–14; 23–24].
The main limitation of our study was the retrospective, single-centre nature at a cardiac surgery referral centre, which may not represent the profile of the entire Brazilian and South American healthcare systems. Therefore, our findings cannot be generalised, and the results may have been influenced by this limitation. A significant strength of our study is that it included one of the largest cohorts of adult patients with definite IE, with prospectively collected data, in Latin America.