Bibliometric analysis on infective endocarditis

Introduction: Although infective endocarditis (IE) is rare disease, this disease has importance due to its high morbidity and mortality rates. The exact incidence is not known as it is not a reportable disease. Unlike developed countries, the disease affects the young more than the elderly in developing countries. Most of the time, the diagnosis cannot be made at the first examination and the disease is often overlooked. In order to reduce the mortality and morbidity of this disease, it is important to quickly recognize the disease by following current diagnosis and treatment methods, to identify the causative agent and to treat accordingly. Both the epidemiology and the management of IE are changing due to medical advances. This situation may also be reflected in scientific publications. We aimed to analyze the global researches on IE. Material and methods: The Scopus database was searched for bibliometric analysis without selecting document type. Data were retrieved for the time period January 1, 1940 and Semptember 26, 2021, containing the keywords " Infective’’ and’’endocarditis " in their title. Results: 7911 publications were included in the study. The first publication was made in the year 1891. Most of the publications were research articles [n=5784 (73.11%)] and were from the United States of America (USA) [n =1622 (20.50%)]. Japan, France, United Kingdom and Spain were also in the top 5 publishing countries on IE. Conclusions: Infective endocarditis is still an important reason of mortality, and there are many unanswered questions about the managament and preventation of this disease. This situation reflected the scientific publications. Since this is a global problem, not just some developed countries involved in the IE research, also more countries should be encouraged to participate the studies on IE.


INTRODUCTION
Infective endocarditis (IE) is defined as infection of heart valves (natural or prosthetic), mural endocardium and intracardiac (CI) devices (permanent pacemakers and/or defibrillators). Although it is rare (3-10/100,000 cases), mortality rates are high. Commonly causative microorganisms are streptococcus, staphylococci and enterococci [1,2]. Despite advances in diagnosis and treatment, in-hospital mortality rate is about 20%. According to the clinical situation and the causative microorganism, more than 1/3 of the patients die within a year. Today, IE patients are older and have more comormidities compared to patients in previous years. Again, an increase in IE cases associated with health-care and CI device associated. The causative microorganisms are more pathogenic and have multiple antibiotic resistance [2]. In order to reduce the mortality and morbidity of this disease, cardiological examinations of the disease (transthoracic echocardiography / transesophageal echocardiography) should be performed quickly. It is critical to identify the causative microorganism and to administer antibiotic therapy for the causative agent. However, most of the patients cannot be diagnosed at their first application, the diagnosis can be made after 3 months in about half of them, and the disease is often overlooked. Patients with IE can be followed by specialist physicians from many different branches [3]. IE occurs much more frequently, in men (60-70%), in the elderly, in patients with underlying heart valve disease, underlying chronic renal failure, hemodialysis patients, solid organ or hematopoietic stem cell transplantation patients [2,3]. The management of patients with IE always adheres to current recommendations. In order for it to be carried out appropriately, it is necessary to ensure that every diagnosis and treatment process of IE is carried out needs to be standardized [3]. In summary, both the epidemiology and the management of IE are constantly changing due to medical advances. Continuously updated diagnostic and treatment guidelines provide tailored advice on disease management [3,4]. This situation may also be reflected in scientific researches. With this study we aimed to analyze the global researches on IE.

MATERIALS AND METHODS
Bibliometric data analysis method was used in this study to analyze publications on IE. Studies on IE were analyzed according to publication years, authors and institutions, themes, citations, keywords, funding institutions, methods and samples. The Scopus database was searched for bibliometric analysis without selecting document type. Data were retrieved for the time period January 1, 1940 and Semptember 26, 2021, containing the keywords "infective'' and''endocarditis" in their title. The searches were performed on a single day Semptember 26, 2021 to avoid bias as the database has daily updates. Duplications were included in the review only once. The obtained data were analyzed in the Excel forms created by the researchers. The data analyzed with both quantitative and qualitative methods. As it is intended to add a general perspective on IE, only top rated countries, afiliations and authors were analyzed in details. Canakkale On Sekiz March University's online library and digital resources were used to access information.

ETHICAL APPROVAL
The study complied with the Helsinki Declaration, which was revised in 2013. Ethics committee approval is not required as there is no human or animal research.

RESULTS
We reached totally 7911 publications on IE in the Scopus database, and the first publication was made in the year 1891 (   Gilbert Habib from France, was the most productive author on IE with 104 articles. Also Bruno Hoën from France was at the 2 nd and Franĉois Delahaye from France was at the third place in the ranking. In summary, the top 3 ranked authors were from France ( Figure 3).
The study of Li JS, from USA was the top cited document with 2529 cites ( Table 2).

DISCUSSION
Infective endocarditis is defined as the infection of the inner surface of the heart valves and is a disease whose results are feared especially in the field of cardiology and infectious diseases. Mortality rates are still quite high, despite advances in medicine. To prevent the development of this disease, prophylactic antibiotic treatments may be required for patients who will undergo some invasive procedures and those with underlying valve disease. It is heterogeneous in terms of etiology, clinical manifestations and course of the disease. In fact, in some patients, medical treatments may be insufficient so patients may require surgery. Longstanding debates such as the timing of this surgery or the role of antibiotic prophylaxis remain unresolved [5,6]. Infective endocarditis is a disease that can be fatal if not diagnosed and treated appropriately and it has been known since the end of the 1800s [4]. Many disciplines work together in the management of this disease. The first guidelines on the management of this complex disease have been available in the medical literature since the 1980s. The first endocarditis guideline was published from Germany [7]. With this study we aimed the analyse of the publications on IE. Although many bibliometric analyzes have been made in the field of cardiology, no similar study has been found in the available literature regarding our study [8][9][10]. The Web of Science Core Collection (WoSCC) and Scopus databases are frequently used databases in bibliometric analysis. With this analysis method, publications can be analyzed using many methods such as visualization, citation analysis, mapping techniques [10][11][12]. Ready-to-use databases can be used, as well as database mining can be preferable. With this quantitative method, parameters such as the the leading country in a topic, authors, publication years, and contents of the publications [8][9][10][11][12][13][14]. We conducted a bibliometric study with the Scopus database, as it is the widest range on publications.
According to the Pubmed Medline search results, it was determined that the first publication on IE was published in the year 1848. While the publications on IE remained stagnant until the 1950s, a rapid increase was observed afterwards. Especially after the 1980s, the number of publications on IE did not fall below 500/year/publication [15]. In our study, it was determined that there was an increase in the number of publications after the year 1975 and the first publication was made in the year 1891. This may be due to the different journals take place in both databases.
In a bibliometric study, in which the 100 most cited articles in the field of cardiology were evaluated, it was found that most of the publications were published in the USA [8]. Our findings were similar. But, an interesting finding of our study was that, although the most of the publications were published from the USA, when evaluated on the basis of authors the first 3 ranked authors were from France. The most cited journal with 100 articles was Circulation with 36, followed by the European Heart Journal with 28 in Shuaib's study [8]. But in our study, the most cited publications were Clinical Infectious Diseases, The American Journal of Medicine, and the European Heart Journal. This may be related to the fact that IE is a subject that also concerns the field of infectious diseases. The difference in publications and reports for IE may have been caused by the use and availability of additional modalities used in the diagnosis of the disease. There are many modalities that can be used in the diagnosis of IE. Echocardiography is very useful in diagnosing IE and detecting complications. Echocardiography has 75% sensitivity and 90% specificity in detecting vegetations [16].  Multislice computed tomography is useful in imaging prosthetic valve abscess, pseudoaneurysm and fistula where echocardiographic imaging is insufficient [17]. In recent years, single-photon emission computed tomography (SPECT/CT) and positron emission tomography (PET/CT) have been used in the diagnosis of endocarditis [18,19]. The sensitivity of Duke criteria in prosthetic valve and intracardiac device-related infections is low, and these new imagings are very useful [20].
Death is observed in one fifth of the patients hospitalized with the diagnosis of endocarditis [21,22]. Early diagnosis and treatment are important in line with current recommendations due to prosthetic valve, advanced age and additional diseases that adversely affect the prognosis [23].

CONCLUSIONS
In fatal endocarditis, preventive measures should be followed and new imaging methods should be used adequately in the diagnosis. Early diagnosis and treatment with a multidisciplinary approach by forming an endocarditis team will positively affect the prognosis. Infective endocarditis is still an important reason of mortality, and there are many unanswered questions about the managament and preventation of this disease. This situation reflected the scientific publications. Since this is a global problem, not just some developed countries involved in the IE research, also more countries should be encouraged to participate the studies on IE.