Infective endocarditis
Infective endocarditis is an infection of the inner surface of the heart, usually the valves.[1] Signs and symptoms may include fever, small areas of bleeding into the skin, heart murmur, feeling tired, and low red blood cell count.[1][8] Complications may include backward blood flow in the heart, heart failure – the heart struggling to pump a sufficient amount of blood to meet the body's needs, abnormal electrical conduction in the heart, stroke, and kidney failure.[1][2][8][9]
Infective endocarditis
Bacterial endocarditis
Fever, small areas of bleeding into the skin, heart murmur, feeling tired, low red blood cells[1]
Valvular insufficiency, heart failure, stroke, kidney failure[1][2] Blood clot in a lung artery (pulmonary embolism)[3] Enlarged and painful spleen, kidney damage, damage to the distal extremities such as fingers and toes.[4]
Based on symptoms, blood cultures, ultrasound[1]
25% risk of death[6]
5 per 100,000 per year[6]
The cause is typically a bacterial infection and less commonly a fungal infection.[1] Risk factors include valvular heart disease, including rheumatic disease, congenital heart disease, artificial valves, hemodialysis, intravenous drug use, and electronic pacemakers.[6][10][5] The bacteria most commonly involved are streptococci or staphylococci.[1] Diagnosis is suspected based on symptoms and supported by blood cultures or ultrasound of the heart.[1] There is also a noninfective form of endocarditis.[1]
The usefulness of antibiotics following dental procedures for prevention is unclear.[11] Some recommend them for people at high risk.[1] Treatment is generally with intravenous antibiotics.[1] The choice of antibiotics is based on the results of blood cultures.[1] Occasionally heart surgery is required.[1]
The number of people affected is about 5 per 100,000 per year.[6] Rates, however, vary between regions of the world.[6] Infective endocarditis occurs in males more often than in females.[1] The risk of death among those infected is about 25%.[6] Without treatment, it is almost universally fatal.[1] Improved diagnosis and treatment options have significantly enhanced the life expectancy of patients with infective endocarditis, particularly with congenital heart disease.[5]
Damaged valves and endocardium contribute to the development of infective endocarditis.[43] Specifically, the damaged part of a heart valve forms a local blood clot, a condition known as non-bacterial thrombotic endocarditis (NBTE). The platelet and fibrin deposits that form as part of the blood clotting process allow bacteria to take hold and form vegetations. As previously mentioned, the body has no direct methods of combating valvular vegetations because the valves do not have a dedicated blood supply. This combination of damaged valves, bacterial growth, and lack of a strong immune response results in infective endocarditis.
Damage to the valves and endocardium can be caused by:[43]
The risk factors for infective endocarditis provide a more extensive list of conditions that can damage the heart.
Not all people with heart disease require antibiotics to prevent infective endocarditis. Heart diseases have been classified into high, medium and low risk of developing IE. Those falling into high risk category require IE prophylaxis before endoscopies and urinary tract procedures.
Diseases listed under high risk include:[58]
Following are the antibiotic regimens recommended by the American Heart Association for antibiotic prophylaxis:[40]
In the UK, NICE clinical guidelines no longer advise prophylaxis because there is no clinical evidence that it reduces the incidence of IE and there are negative effects (e.g. allergy and increased bacterial resistance) of taking antibiotics that may outweigh the benefits.[59]
Antibiotics were historically commonly recommended to prevent IE in those with heart problems undergoing dental procedures (known as dental antibiotic prophylaxis). There is, however, insufficient evidence to support whether antibiotics are effective or ineffective at preventing IE when given prior to a dental procedures in people at high risk.[60] They are less commonly recommended for this procedure.[61]
In some countries e.g. the US, high risk patients may be given prophylactic antibiotics such as penicillin or clindamycin for penicillin-allergic people prior to dental procedures.[30] Prophylactics should be bactericidal rather than bacteriostatic.[30] Such measures are not taken in certain countries e.g. Scotland due to the fear of antibiotic resistance.[62] Because bacteria are the most common cause of infective endocarditis, antibiotics such as penicillin[30] and amoxicillin (for beta lactamase-producing bacteria) are used in prophylaxis.
High-dose antibiotics are the cornerstone of treatment for infective endocarditis. These antibiotics are administered by the intravenous (IV) route to maximize diffusion of antibiotic molecules into vegetation(s) from the blood filling the chambers of the heart. This is necessary because neither the heart valves nor the vegetations adhering to them are supplied by blood vessels. Antibiotics are typically continued for two to six weeks depending on the characteristics of the infection and the causative microorganisms. Antibiotic treatment lowers the risk of embolic complications in people with infective endocarditis.[12]
In acute endocarditis, due to the fulminant inflammation, empirical antibiotic therapy is started immediately after the blood has been drawn for culture to clarify the bacterial organisms responsible for the infection. This usually includes vancomycin and ceftriaxone IV infusions until the infecting organism is identified and the susceptibility report with the minimum inhibitory concentration becomes available. Once this information is available, this allows the supervising healthcare professional to modify the antimicrobial therapy to target the specific infecting microorganism. The routine use of gentamicin to treat endocarditis has fallen out of favor due to the lack of evidence to support its use (except in infections caused by Enterococcus and nutritionally variant streptococci) and the high rate of complications.[63] In cases of subacute endocarditis, where the person's hemodynamic status is usually stable, antibiotic treatment can be delayed until the causative microorganism can be identified.
Viridans group streptococci and Streptococcus bovis are usually highly susceptible to penicillin and can be treated with penicillin or ceftriaxone.[64] Relatively resistant strains of viridans group streptococci and Streptococcus bovis are treated with penicillin or ceftriaxone along with a shorter two-week course of an aminoglycoside during the initial phase of treatment.[64] Highly penicillin-resistant strains of viridans group streptococci, nutritionally variant streptococci like Granulicatella sp., Gemella sp., Abiotrophia defectiva,[65] and Enterococci are usually treated with a combination therapy consisting of penicillin and an aminoglycoside for the entire duration of 4–6 weeks.[64]
Some people may be treated with a relatively shorter course of treatment[64] (two weeks) with benzyl penicillin IV if infection is caused by viridans group streptococci or Streptococcus bovis as long as the following conditions are met:
Additionally, oxacillin-susceptible Staphylococcus aureus native valve endocarditis of the right side can also be treated with a short 2-week course of a beta-lactam antibiotic such as nafcillin with or without aminoglycosides.
The main indication for surgical treatment is regurgitation or stenosis. In active infective endocarditis, the surgery should remove enough leaflet tissue to ensure eradication of the infectious process.[66] Subsequent valve repair can be performed in limited disease.[66] Replacement of the valve with a mechanical or bioprosthetic artificial heart valve is necessary in certain situations:[67]
The guidelines were recently updated by both the American College of Cardiology and the European Society of Cardiology. There was a recent meta-analysis published that showed surgical intervention at seven days or less is associated with lower mortality.[68]
Prognosis[edit]
Infective endocarditis is associated with 18% in-hospital mortality.[29] However, adult patients with congenital heart disease can have relatively lower mortality down to 5% due to younger age, right-sided endocarditis and management by multidisciplinary teams. As many as 50% of people with infective endocarditis may experience embolic complications.[12]
Epidemiology[edit]
In developed countries, the annual incidence of infective endocarditis is 3 to 9 cases per 100,000 persons.[43] Infective endocarditis occurs more often in men than in women.[12] There is an increased incidence of infective endocarditis in persons 65 years of age and older, which is probably because people in this age group have a larger number of risk factors for infective endocarditis. In recent years, over one-third of infective endocarditis cases in the United States was healthcare-associated.[43] Another trend observed in developed countries is that chronic rheumatic heart disease accounts for less than 10% of cases. Although a history of valve disease has a significant association with infective endocarditis, 50% of all cases develop in people with no known history of valvular disease.