endocarditis

endocarditis
Name	Endocarditis
Synonyms	Infective endocarditis
Caption	A vegetation on the mitral valve, a characteristic finding.
Field	Cardiology, Infectious disease
Symptoms	Fever, heart murmur, petechiae
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, Rheumatic heart disease
Diagnosis	Duke criteria, Echocardiography, Blood culture
Differential	Rheumatic fever, Atrial myxoma, Systemic lupus erythematosus
Prevention	Antibiotic prophylaxis
Treatment	Antibiotics, Cardiac surgery
Medication	Vancomycin, Gentamicin, Ceftriaxone
Frequency	3-10 per 100,000 per year

endocarditis is a life-threatening inflammatory condition affecting the inner lining of the heart chambers and valves. It is most commonly caused by microbial infection, leading to the formation of destructive vegetations composed of platelets, fibrin, and microorganisms. The disease poses significant risks of embolic complications and valvular destruction, requiring prompt diagnosis and aggressive management. Its clinical presentation can range from an indolent, subacute illness to a fulminant, septic picture.

Definition and classification

The condition is formally defined as an infection involving the endocardial surface of the heart, typically the valves. It is primarily classified as either native valve or prosthetic valve, with the latter carrying a higher mortality and often involving organisms like Staphylococcus epidermidis. Another key classification distinguishes between acute and subacute forms, based on the virulence of the causative organism and rapidity of symptom onset. The modified Duke criteria provide a standardized framework for categorizing cases as definite or possible based on clinical, microbiological, and echocardiographic findings.

Causes and risk factors

The most frequent causative agents are gram-positive cocci, with Staphylococcus aureus now surpassing Streptococcus viridans as the leading cause in many regions, particularly associated with healthcare exposure. Other significant pathogens include the HACEK organisms and enterococci. Major risk factors predisposing individuals include the presence of a prosthetic heart valve, a history of rheumatic heart disease, congenital heart defects like ventricular septal defect, and behaviors such as intravenous drug use. Procedures causing transient bacteremia, like dental extractions, can also seed infection in susceptible individuals.

Pathophysiology

The disease process typically begins with endothelial damage, often from turbulent blood flow across an abnormal valve, which allows platelets and fibrin to deposit. Circulating microorganisms, introduced during episodes of bacteremia, adhere to these sterile vegetations and proliferate. This leads to the formation of infected masses that can locally destroy valvular tissue, causing regurgitation or obstruction. Fragments of these vegetations can embolize to distant sites, causing complications like splenic infarction or mycotic aneurysm in the cerebral circulation.

Signs and symptoms

Clinical manifestations are highly variable. Fever and a new or changing heart murmur are classic findings. Peripheral signs may include petechiae, splinter hemorrhages, Osler's nodes, and Janeway lesions. Embolic phenomena can present as a stroke, causing focal neurological deficits, or as flank pain from a renal infarct. Subacute cases may feature nonspecific symptoms like fatigue, weight loss, and night sweats, mimicking other chronic illnesses such as tuberculosis or lymphoma.

Diagnosis

Diagnosis hinges on integrating clinical suspicion with key investigations. The cornerstone is obtaining multiple sets of blood cultures before initiating antimicrobial therapy. Echocardiography, particularly transesophageal echocardiography, is critical for visualizing vegetations, abscesses, or valvular dysfunction. The Duke criteria formally combine these findings with predisposing conditions and vascular phenomena for diagnosis. Other supportive tests may include an elevated erythrocyte sedimentation rate, anemia, and microscopic hematuria.

Treatment

Management requires prolonged intravenous antimicrobial therapy, often for four to six weeks, tailored to the identified pathogen and its susceptibility. Common regimens include combinations like nafcillin and gentamicin for sensitive Staphylococcus aureus, or vancomycin for resistant strains. Indications for early cardiac surgery include heart failure from severe valvular regurgitation, uncontrolled infection despite antibiotics, large vegetations with high embolic risk, or infection involving a prosthetic valve. Surgery may involve valve repair or replacement.

Prevention

Preventive strategies focus on antibiotic prophylaxis for high-risk patients undergoing procedures likely to cause bacteremia. Guidelines from the American Heart Association recommend prophylaxis for those with prosthetic valves, previous history of the disease, certain congenital heart diseases, or cardiac transplant recipients with valvulopathy. The recommended regimen often involves amoxicillin before dental procedures. For all patients, maintaining good oral hygiene and promptly treating other foci of infection are essential general measures. Category:Cardiovascular diseases Category:Infectious diseases