Surgery is commonly required before the end of antibiotic treatment if the valve is destroyed, leading to cardiac failure. Cardiac abscesses are more common in patients with prosthetic valves and those with staphylococcal infection. The onset of atrioventricular heart block is an ominous sign. Extension of the abscess into supporting structures makes surgical treatment difficult and can be avoided by early echocardiographic assessment and intervention. Vegetations of dimensions over 10 mm tend to carry a greater risk of embolization and are less likely to be cured by medical treatment alone.

The purpose of surgery is to remove infected tissue, obliterate abscess cavities, close any fistula or defect, and remove vegetations, usually by valve replacement. The timing of surgery can be difficult and depends on the presence of a prosthetic valve, the site, complications and organism, the delay in diagnosis, the efficacy of antibiotic treatment, and the progression of the disease. If the patient remains cardiovascularly compensated, surgery can be delayed until completion of antibiotic treatment, depending on the degree of dysfunction. Severe aortic regurgitation usually requires surgery because of the poor eventual prognosis. Severe mitral regurgitation (usually papillary rupture or valvular perforation) may open to a limited repair. If pulmonary edema develops or cardiac output falls and renal failure develops, surgery will usually have to be performed as an emergency procedure following ultrasound examination. Transient pulmonary edema may be caused by an arrhythmia or chordae tendinae rupture, but if only aortic valve disease is found, surgery should be considered after 3 weeks of antibiotic treatment.

Persistence of bacteremia during antibiotic treatment can be caused by resistance of the pathogen, intracardiac or metastatic abscesses, or mycotic aneurysms. Staphylococcal prosthetic valve endocarditis inevitably requires valve replacement, as do half of the cases of staphylococcal native valve endocarditis. Extension of an abscess into the interventricular septum causes atrioventricular block and indicates the need for urgent surgery. Aortic and prosthetic valve disease is most often complicated by abscess formation (up to 50 per cent) which makes surgical correction difficult and risky.

Surgery is needed when a new murmur appears or emboli are produced. Perivalvular leaks are common following valve replacement. Transesophageal echocardiography is the most sensitive means of confirming the presence of an abscess. Surgical intervention should not await sterilization by antibiotics because the prognosis is poor. Appearance of a pansystolic murmur in native aortic valve disease suggests septal perforation and, if confirmed by echocardiography, is another indication for surgery. Emboli occur in a third of cases of endocarditis and account for a quarter of the deaths, particularly when caused by staphylococci, fungi, and Gram-negative bacilli. More than two episodes of embolization should be an indication for surgery to remove the vegetation.

Infected valves can be replaced by mechanical or bioprosthetic valves. Homografts are often used because they do not need anticoagulation and facilitate repair of abscess cavities. Some cases of mitral valve disease can be adequately treated by excision of the vegetations. Tricuspid valve disease in drug abusers can be treated by excision of the valve or the vegetations. Insertion of bioprosthesis is not always necessary in these patients, and there is a risk of recurrence if abuse continues. Mortality in native valve disease has been reported in 5 to 18 per cent of cases, being higher in those with annular abscesses or aneurysms or multiple valve replacement. Surgery for prosthetic valve endocarditis results in death in 13 to 30 per cent of cases depending on the time since insertion of the valve.

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