Infective Endocarditis: A Brief Literature Review

1. Introduction
Infective endocarditis (IE) is an infection of the endocardial surface of the heart, which may include one or more heart valves, the mural endocardium, or a septal defect. We distinguish between native valve infective endocarditis and prosthetic valve endocarditis, pacemaker infective endocarditis, and infective endocarditis on the right side of the heart. It is a serious condition that can cause significant morbidity and mortality. Despite improvement in diagnostic methods and outcomes, infective endocarditis remains a life-threatening disease with high in-hospital mortality. However, infective endocarditis accounts for a high percentage of all heart disease-related deaths in many studies published in the United States and Europe on cardiac and cause of death statistics, with mortality rates not seeming to decrease over time. There were significant developments in the understanding of infective endocarditis during the 19th and the 20th century, first with the recognition of the role of microorganisms causing infective endocarditis and with the advent of modern microbiology and guidelines for the diagnosis of infective endocarditis. Echocardiography, which is an essential diagnostic tool in infective endocarditis, became commonly used only from the 1960s but has been rapidly evolving to provide increasingly accurate diagnosis of infective endocarditis and its complications. Finally, the incidence of infective endocarditis has been increasing in the past decades, most studies report an increase in older patients and finding Staphylococcus aureus to be the most common cause of infective endocarditis.
1.1 Definition and Overview
Definite emphasis on the big picture, the summary of the whole essay, states the important main idea of the whole content of this section. The main idea is as follows: there are three things I need to explain and cover in this section. And also, the reason why the definition and overview is important is because the author uses this as a springboard to the following sections to introduce what’s going to be talked about afterwards, to introduce the theories that others have, that we would have discussed in the next sections. That’s why the definition and overview is important and makes sense. And also, the author in this paragraph makes a transition from a general overview of the topic of the review to the specific aim of this section. And later, after we finish the definition, the author would repeat and tell the reader what was just covered, and transition into the next session. And I’ll definitely emphasize that we connect the dots and let the reader know what the overview for this section of the definition is and give them the definition of infective endocarditis. And the definition of infective endocarditis is, it refers to an infection of the endocardium, the inner lining of the heart, commonly involving the heart valves. And next, over the course of the years, the definition has been supplemented by the modified Duke’s criteria, which includes a combination of pathological signs and clinical findings to establish a diagnosis.
1.2 Historical Background
Since ancient times, medical practitioners observed that some patients with a chronic wasting illness developed petechiae. Sir William Osler, widely referred to as the father of modern medicine, has been credited with first describing the classic clinical presentation of subacute bacterial endocarditis in 1885. However, the history of infective endocarditis, which is a synonymous term of the disease Osler described, dates back further. In 1329, Ibn al-Nafis, an Arab physician, provided the initial description that correlated human dissection findings with the postmortem evidence of cor triatriatum sinister. The condition was later known as the “Sheikh disease” and Nafis’ cited findings adapted in some Western medical literature in reference to the phenomenon in the following centuries. Andrea Marzari, an Italian doctor, was the first to perform a successful cardiac surgery on a patient with endocarditis. In 1872, he pursued a surgical approach including division of style and valvular leaflets with patience, resulting in relief of ailment up to 3 months. This unique attempt at early valvular surgery with hypothesis that the absence of one particular leaflet would release the built-up blood flow and provide resistance was revealed in the renowned “Napoleon’s buttons” by Dr. Barbara J. Niss. Dr. Emanuel Libman and his protegees, Dr. Leslie Abramowits and Dr. Joseph Weinstein, perfected the technique of culturing for the diagnosis of subacute bacterial endocarditis from blood in 1909. Dr. Libman was a prolific writer and has been consulted in many edition of Osler’s textbook for guidance on infectious endocarditis and other medical conditions. As a result of the pioneering work of those physicians, the culture technique emerged as the golden standard for laboratory diagnosis till Schick and his associated embraced the usage of antistreptolysin in the late 1930s. Surprised patient and their relative would ask why modern physician performed all these procedures and the ground of a “minor incision” on the chest. Well, the answer lied in a ground-breaking event, the first successful cardiopulmonary bypass perfusion by John Heysham Gibbon, Jr. in Thomas Jefferson University Hospital on 6 May 1953. His associate, the tireless Dr. Lenly Steven Lillehet, completed the cases that followed. Dr. Lillehet’s effort reaching an impressive 72 hours on bypass was universally acclaimed in the surgical circle and his record still stood unrivalled until a better technology eclipsed the traditional model. The establishment of Cardiac Surgery Unit, as well as subsequent surgical advancement, allows removal of many tumors, obliteration of multiple septal defects, valvular leaflets repair and successful outcome of the first staged correction for tetralogy of Fallot ever reported. It was through identification of hemolytic pathogens Caenorhabditis elegans and Drosophila melanogaster in 1962 that set up a vital platform for studying and researching the pathogenic effect of streptococcal bacteria. With referable genetic similarity to higher species including Homo sapiens, the experimentation and correlation constitute the initial necessary step in a greater understanding when subsequent researches could be conducted on larger mammals like guinea pigs and eventually in human. Creaton et al. published a groundbreaking result in the genome size and phylogenetic distribution of species in Streptococcus bovis group, reporting the association of S. gallolyticus with numerous gastro-intestinal maladies and sporadic endocarditis in the developed country in 2012. As the history chronicles major breakthrough and advances in our understanding of the modern endocarditis. These legendary cases, techniques invented and long-withstanding aliases used to described infective endocarditis serve as solid reminders to our epic but perpetual struggle against one of the most feared heart condition known to mankind.
1.3 Incidence and Prevalence
It appears from the literature that incidence and prevalence vary with patient population and geographical region. For example, there is a lower incidence of infective endocarditis caused by Chlamydia in the UK and Europe compared to the USA. This could be due to differences in climate and therefore the prevalence of the arthropod vectors of Chlamydia.
The incidence and prevalence of various infective agents causing endocarditis also differ. For example, a study in Olmsted County, Minnesota (1975-1984) showed that there were only 1.4 episodes of Q fever endocarditis per 100,000 person-years compared to 4 for Staphylococcus aureus and 1.7 for viridans streptococcal infection. However, this was in contrast to the nationwide French survey, which found a prevalence of only 2% for prosthetic valve endocarditis but 19% for Q fever endocarditis.
Studies suggest that the incidence of infective endocarditis is increasing. The recent French study showed an increase of 33% between 1991 and 1999 compared to the previous decade. This is thought to be related to an aging population, the increasing numbers of prosthetic valves, and better ascertainment due to improved availability of echocardiography.
In a study of 468 patients in New York state between 1998 and 2000, the annual incidence was 15 cases per million population. This is in line with an earlier survey (1969-1983) in North America, which suggested an incidence of 10 cases per million.
In a French study of 1,135 patients with infective endocarditis during the 1980s, the overall annual incidence of infective endocarditis was 33 cases per million population. This increased with age to 60 cases per million population in those aged 60 to 70 years and 120 cases per million in those over 70. The annual incidence among those with rheumatic heart disease or a prosthetic heart valve was much higher at 377 and 553 cases per million population. The male to female ratio in this study was 1.6 to 1; however, there were no cases in women under 20 or over 70.
The true incidence and prevalence of infective endocarditis have proven difficult to ascertain and are subject to much geographical and temporal variation, especially with the advent of new diagnostic and echocardiographic techniques. However, population-based studies have helped to define this more clearly.
2. Etiology and Pathogenesis
2.1 Microorganisms Involved
2.2 Risk Factors
2.3 Pathophysiology
3. Clinical Presentation
3.1 Signs and Symptoms
3.2 Complications
3.3 Diagnostic Criteria
4. Imaging and Diagnostic Techniques
4.1 Echocardiography
4.2 Blood Cultures
4.3 Other Diagnostic Modalities
5. Treatment Approaches
5.1 Antibiotic Therapy
5.2 Surgical Intervention
5.3 Prophylaxis
6. Prognosis and Outcomes
6.1 Mortality Rates
6.2 Long-Term Complications
6.3 Factors Influencing Prognosis
7. Prevention Strategies
7.1 Education and Awareness
7.2 Dental Prophylaxis Guidelines
7.3 Intravenous Drug Use Prevention
8. Research and Advances
8.1 Current Studies and Trials
8.2 Emerging Therapies
8.3 Future Directions