Uncontrolled Infection
This is the second most common indication for surgery[8] and encompasses persistent bacteremia, extension of perivalvular infection and resistant organisms.
Persistent Bacteremia
Persistent sepsis from an ongoing bacteremia after 5–7 days, or lack of clinical improvement after 1 week of appropriate antibiotic therapy is generally an indication for surgery. An extracardiac abscess (e.g., renal or splenic) should also be sought and if excluded early surgery should be undertaken. Persistent sepsis is more common with larger vegetations that are more difficult for antibiotics to penetrate and in IE secondary to more aggressive organisms, including Staphylococcus aureus.[19] Current guidelines indicate that surgery should be considered if fever or positive blood cultures persist after 7 days of appropriate therapy.[5,6]
An important distinction is the patient who develops recurrent fever after initially favorable progress. In this setting, antibiotic sensitivity or an alternative source of infection (including the possibility of central line colonization) are likely and surgery should only be considered once these have been excluded with confidence.
Relapse following initially successful treatment is more common in patients with either nonstreptococcal endocarditis or prosthetic valve endocarditis. Surgery should also be considered in these patients.
Perivalvular Extension
Extension of IE beyond the valve leaflets, apparatus and annulus is associated with increased mortality, development of congestive heart failure and a higher likelihood of surgery.[39–42] Perivalvular extension in IE is the most common cause of uncontrolled infection, affecting 10–40% of patients with native valve IE, and is most frequent in IE affecting the aortic valve, when abscess expansion near the membranous septum and atrioventricular node may result in heart block. Periannular infection is of even greater concern in prosthetic valve endocarditis, occurring in 56–100% of patients, and accounting for high mortality in this group.[43]
Clinical clues include persistent fever, new atrioventricular conduction defects and pericardial effusion. Hence, serial ECGs should be performed in these patients although diagnosis is best confirmed by TOE.
Fistula and aneurysm formation due to extension of IE are associated with frequent surgery (87%) and high mortality (41%).[44] Other complications include ventricular septal defects, acute coronary syndromes and third degree atrioventricular block.[45–47] Factors associated with mortality included moderate-to-severe CCF, prosthetic valve involvement and need for an urgent operative procedure. Despite such high-risk surgery, there is no other real alternative, even when the patient remains hemodynamically stable.
Only in patients with small abscesses (<1 cm) in whom fever is controlled with no evidence of the aforementioned complications can a strategy of medical therapy with close clinical and echocardiographic monitoring be implemented.[5]
Resistant Pathogens
Several organisms are resistant to medical therapy and therefore a surgical approach is advocated. S. aureus native valve endocarditis, for example, causes severe valvular damage, large vegetations, embolic complications and poor overall prognosis.[16,19,48] Early surgery should be considered in most cases of native valve endocarditis and all cases of prosthetic valve endocarditis if there is no immediate response to appropriate antibiotic therapy.[19,49] Coagulase-negative cocci such as Staphylococcus lugdunensis are associated with a high rate of cardiac tissue destruction and requirement for early valve surgery.[50]
Fungal IE, secondary to infection with Candida or Aspergillus, is often complicated by bulky vegetations, perivalvular spread and embolic events. Penetrance of antifungal agents, such as amphotericin B, into these large vegetations is poor and early surgery is almost always necessary, particularly when complications are present.[51] In those who are deemed unfit for surgery, long-term antibiotic suppressive therapy can be considered.[52]
Pseudomonas aeruginosa is associated with nosocomial infections. While medical therapy may suffice in right-sided endocarditis, this is rarely effective in left-sided disease. Therefore surgery offers the best prospect of complete cure.[53]
Brucella IE is characterized by an aggressive course with frequent valve destruction, congestive heart failure and abscess formation. Antimicrobial therapy alone is rarely effective and early surgery is recommended.[54]
Coxiella burnetii, the agent responsible for Q fever, is resistant to medical cure and recolonization after successful valve surgery is a frequent event. Surgery is recommended in patients with congestive heart failure, prosthetic valve endocarditis and uncontrolled infection[55] and prolonged postoperative antimicrobial therapy (up to 2 years) is recommended to prevent recurrence.[56]
Surgery provides the only means of eradication of infection when IE is caused by multiresistant organisms, including methicillin-resistant S. aureus and vancomycin-resistant enterococci. Early involvement of microbiology teams is essential to determine the selection and duration of appropriate antibiotic therapy.
In summary, patients with uncontrolled infection from persistent sepsis, perivalvular extension and resistant pathogens should undergo early surgery unless severe comorbidites exist.
Future Cardiol. 2012;8(6):847-861. © 2012 Future Medicine Ltd.
