Endocarditis

Endocarditis is inflammation of the endocardium, the inner lining of the heart, and most clinically important is infective endocarditis, an infection of the heart valves or endocardial surface. It is characterized by vegetations made of microorganisms, platelets, and fibrin on the valves, and it can lead to valve destruction, embolic events, and systemic infection.

Definition

Endocarditis is inflammation of the endocardium; infective endocarditis is an infection of the endocardial surface or heart valves, typically by bacteria, producing vegetations and the potential for valvular damage, embolization, and persistent bloodstream infection (Holland, 2016).

Scope

The entry covers endocarditis as a clinical entity with emphasis on its infective form, including the common causative bacteria, the pathophysiology of vegetation formation, predisposing cardiac and host factors, and the diagnostic framework that combines microbiological and imaging findings. It is a reference overview and does not provide antibiotic regimens, surgical indications, or individualized care.

Core questions

• What is the endocardium, and how does infective endocarditis differ from non-infective endocardial inflammation?
• Which organisms most commonly cause infective endocarditis, and how do native-valve, prosthetic-valve, and device-related disease differ?
• How do vegetations form, and how do they cause valve destruction and embolic complications?
• How is the diagnosis approached using combined clinical, microbiological, and imaging criteria?

Key concepts

• Endocardium and heart valves
• Infective versus non-infective endocarditis
• Vegetations
• Native-valve, prosthetic-valve, and device-related endocarditis
• Staphylococci, streptococci, and enterococci
• Modified Duke criteria
• Embolic and valvular complications

Mechanisms

Infective endocarditis typically begins where the endocardial surface is damaged or turbulent, allowing platelets and fibrin to deposit and form a sterile thrombus. During an episode of bacteremia, circulating organisms adhere to this surface and proliferate, building a vegetation in which bacteria are partly shielded from immune cells. The vegetation can destroy valve tissue, shed septic emboli to distant organs, and sustain continuous release of bacteria into the bloodstream (Holland, 2016; Thuny, 2012). Diagnosis integrates these features through combined microbiological and imaging criteria.

Clinical relevance

Infective endocarditis is an uncommon but serious infection with substantial mortality and a high rate of complications such as heart failure, embolism, and valve destruction, and its diagnosis depends on integrating blood-culture and imaging findings. This entry describes how the entity is defined and conceptualized as a reference; it is not a basis for diagnosis or for individual treatment decisions.

Epidemiology

Infective endocarditis affects a minority of people but carries high morbidity and mortality, and its profile has shifted over time toward more healthcare-associated and prosthetic-material-related disease, with staphylococci, streptococci, and enterococci as the predominant causes (Holland, 2016; Thuny, 2012). Predisposing factors include prosthetic valves, prior endocarditis, certain congenital and acquired valve disease, intracardiac devices, and injection drug use.

History

The clinical picture of bacterial endocarditis was characterized in the late nineteenth century, and before antibiotics the disease was essentially fatal. The modern diagnostic framework was consolidated through the Duke criteria, later modified to incorporate advances in echocardiography and microbiology, and management has increasingly combined prolonged antimicrobial therapy with cardiac surgery for selected cases (Baddour, 2015; Delgado, 2023).

Debates

Who should receive antibiotic prophylaxis before procedures?

Guidelines have narrowed the recommended use of antibiotic prophylaxis to patients at highest risk, reflecting uncertainty about how much procedure-related bacteremia contributes to endocarditis relative to everyday bacteremia, and the recommendation continues to be debated and revised.

Seminal works

• holland-2016
• thuny-2012
• baddour-2015

Frequently asked questions

What is a vegetation in endocarditis?

A vegetation is a mass of microorganisms, platelets, and fibrin that forms on an infected heart valve or endocardial surface; it is the hallmark lesion of infective endocarditis and can destroy valve tissue and break off to cause emboli.

Which bacteria most commonly cause infective endocarditis?

Staphylococci (especially Staphylococcus aureus), streptococci, and enterococci are the predominant causes of infective endocarditis, with the exact distribution depending on whether the disease is native-valve, prosthetic-valve, or healthcare-associated.