infective endocarditis

infective endocarditis
Name	Infective endocarditis
Synonyms	Bacterial endocarditis
Caption	A vegetation on the mitral valve seen during surgery.
Field	Infectious disease, Cardiology
Symptoms	Fever, heart murmur, Janeway lesions
Complications	Heart failure, stroke, septic embolism
Types	Acute, subacute
Causes	Bacteria (e.g., Staphylococcus aureus, Streptococcus viridans), fungi
Risks	Prosthetic heart valve, intravenous drug use, congenital heart disease
Diagnosis	Duke criteria, echocardiography, blood culture
Treatment	Antibiotics, cardiac surgery
Medication	Vancomycin, gentamicin, ceftriaxone

infective endocarditis is a serious infection of the endocardium, typically involving the heart valves. It is characterized by the formation of infected masses, known as vegetations, composed of platelets, fibrin, and microorganisms. The condition can lead to severe complications such as valvular destruction, embolism, and sepsis, and requires prompt diagnosis and aggressive treatment.

Definition and classification

Infective endocarditis is defined as an infection of the endocardial surface of the heart, which includes the native valves, prosthetic valves, or the mural endocardium. It is classified based on the acuity of presentation and the causative microorganism. Acute infective endocarditis is a rapidly progressive illness often caused by Staphylococcus aureus, while subacute infective endocarditis has a more indolent course, frequently associated with Streptococcus viridans. Another critical classification is based on the site of infection, distinguishing between left-sided endocarditis and right-sided endocarditis, the latter being more common in intravenous drug users.

Causes and risk factors

The primary causes are bacteria, with Staphylococcus aureus and Streptococcus viridans being the most common pathogens in the United States and Europe. Less frequently, Enterococcus faecalis, the HACEK group of organisms, and fungi like Candida albicans are implicated. Major risk factors include the presence of a prosthetic heart valve, a history of rheumatic heart disease, congenital heart defects such as ventricular septal defect, and behaviors like intravenous drug use. Invasive procedures, including dental procedures and the use of intravascular catheters, can facilitate bacteremia that seeds the endocardium.

Pathophysiology

The pathogenesis typically begins with endothelial damage, often from turbulent blood flow across an abnormal valve, leading to the deposition of platelets and fibrin to form a nonbacterial thrombotic vegetation. During transient bacteremia, circulating microorganisms adhere to this sterile vegetation, colonize it, and proliferate, forming an infected mass. This process is mediated by microbial surface components recognizing adhesive matrix molecules, which allow pathogens like Staphylococcus aureus to bind to host tissues. The resulting vegetation can cause local destruction, leading to valvular regurgitation, or fragment, causing septic emboli to organs like the brain, spleen, and kidneys.

Clinical features

Clinical manifestations are highly variable and can include constitutional symptoms like fever, chills, and night sweats. Specific findings may involve the cardiovascular system, such as a new or changing heart murmur, and peripheral stigmata of embolization like splinter hemorrhages, Osler's nodes, and Janeway lesions. Complications can present as heart failure due to valvular damage, neurological deficits from a stroke, or signs of septic shock. Right-sided endocarditis, often associated with Staphylococcus aureus in intravenous drug users, may present with pulmonary embolism and pleuritic chest pain.

Diagnosis

Diagnosis relies on the integration of clinical, microbiological, and echocardiographic findings, formalized by the Duke criteria. Key investigations include obtaining multiple sets of blood cultures to identify the causative organism. Echocardiography is crucial, with transesophageal echocardiography being more sensitive than transthoracic echocardiography for detecting vegetations, especially on prosthetic valves. Other supportive tests may include an electrocardiogram to assess for conduction abnormalities, and computed tomography to evaluate for embolic complications in the brain or abdomen.

Treatment

Treatment involves prolonged administration of bactericidal antibiotics, tailored to the identified pathogen and its antibiotic susceptibility. Common regimens include penicillin or ceftriaxone for sensitive Streptococcus viridans, and vancomycin for methicillin-resistant Staphylococcus aureus. Surgery, often performed at institutions like the Cleveland Clinic or Mayo Clinic, is indicated for complications such as severe heart failure, uncontrolled infection, large vegetations, or prosthetic valve dysfunction. The timing of surgery is a critical decision, often involving a multidisciplinary team from cardiology and cardiac surgery.

Prevention and prognosis

Prevention focuses on antibiotic prophylaxis for high-risk patients, such as those with prosthetic heart valves or certain congenital heart diseases, undergoing high-risk procedures like dental extractions. Guidelines from the American Heart Association and the European Society of Cardiology have refined these recommendations. Prognosis depends on factors like the causative organism, the presence of complications, and the timing of intervention. Despite advances in antimicrobial therapy and surgery, mortality remains significant, particularly for infections involving Staphylococcus aureus or fungi, and in patients with comorbidities like diabetes mellitus or chronic kidney disease.

Category:Infectious diseases Category:Cardiovascular diseases