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SURGERY IN ACTIVE INFECTIVE ENDOCARDITIS

SURGERY IN ACTIVE INFECTIVE ENDOCARDITIS

Preoperative Assessment of the Patient with Infective Endocarditis
Surgery in Patients with Native Valve Infective Endocarditis
 
Congestive Heart Failure
 
Infection with Resistant Organisms
 
Extravalvular Extension of Infection
 
Other Reasons for Operative Intervention
Prosthetic Valve Endocarditis
Bibliography

Infective endocarditis (IE) often results in death if not diagnosed and treated. Since the advent of effective bactericidal antimicrobials, mortality has declined from almost 100% to 20%-50%, depending on pathogen, host, and complications. Congestive heart failure (CHF) represents a common cause of death in these patients. The most common cause of CHF is valvular insufficiency. Surgery plays a major role in patients with complications of IE. Goals of surgery are to remove infected tissue, reestablish valve function, and restore normal cardiac mechanics.
Preoperative Assessment of the Patient with Infective Endocarditis
Many patients with IE suffer no significant complications and can be managed successfully with appropriate antimicrobials and no surgical intervention. For all persons in whom this condition is diagnosed, routine laboratory data should be obtained to use as a baseline, monitor therapy, and assess for complications. Standard blood tests include CBC, urinalysis, determination of hepatic and renal function, and sedimentation rate; the role of serum bactericidal testing is controversial. Additionally, patients should have an electrocardiogram and echocardiography performed early in the course of disease. These are obtained to establish a baseline against which to compare future changes and look for abnormalities that could portend complications. The electrocardiogram can document conduction abnormalities that might represent extension of infection into the conducting system. Bundle blocks and first- and third-degree heart block have been reported as complications of IE, most commonly in aortic valve disease. The former is rather common and may indicate only inflammation. However, prolongations of the PR interval may also be associated with a high risk for complete heart block and the probability of deep abscess formation. Thus, patients with prolonged PR intervals should be closely monitored. Complete heart block complicates about 4% of cases of IE. Ischemia or acute myocardial infarction documented by electrocardiogram may represent coronary embolization from an infected aortic vegetation rather than primary coronary artery disease.
Most authorities now recommend that transesophageal echocardiography (TEE) be performed on most patients with IE, although absolute indications are not known. In competent hands, a positive study result can demonstrate vegetations (and thus define the presence of IE) and identify complications. TEE is superior to transthoracic echocardiography (TTE) in the visualization of both vegetations and complications, which can be anatomic or hemodynamic in nature. Examples of such complications include valve perforation, abscesses, and pericardial effusion. Hemodynamic complications may include valve incompetence, fistulae, and intracardiac thrombi. TEE is now considered the most reliable noninvasive test for defining this disease. However, it may not differentiate between active and healed vegetations and may not be able to discriminate between thickened valves or valvular nodules and vegetations. Thus, it should be utilized primarily in patients whose risk for IE is considered significant. Recent data prove the capacity of TEE to document IE and demonstrate valve ring abscesses not noted by other echocardiographic studies. Authorities now feel that TEE is at least 90% sensitive and specific in the diagnosis of IE. As an example, patients with abscess complicating IE were identified on only 13 of 44 TTE studies, compared with 40 of 44 by TEE. Both sensitivity and specificity were dramatically increased. Alternatively, a technically comprehensive TEE demonstrating no changes of IE virtually rules out that disease. Doppler should be employed in such clinical situations as (a) follow-up of patients with staphylococcal bacteremia (not considered to have IE) before discontinuation of antimicrobials, (b) assessment of patients with IE who remain febrile or persistently bacteremic, and (c) assessment of patients with IE plus conduction defects, CHF, or other potential intracardiac complications. It is the opinion of the author that selected patients with IE documented clinically, who show a prompt response to antibiotics and have no evidence of complications, may be managed without echocardiography.
Although many cardiologists appear reluctant to perform cardiac catheterization in patients with IE, it is occasionally useful when TEE has not provided adequate diagnostic or anatomic information. Cardiac catheterization can identify site of infection, assess for fistulae and abscesses, and evaluate hemodynamic status. Risk for complications is similar to that seen with cardiac catheterization in other groups, and thus it is not contraindicated because of the presence of active IE. Controlled studies of TEE versus cardiac catheterization to identify complications of IE have not been performed.
Surgery in Patients with Native Valve Infective Endocarditis
Several studies demonstrate improved outcome of patients with IE who have undergone surgery after medical failure. Surgery should be performed when clinically indicated and should not be based on duration of effective antibiotic therapy. Benefits may be long-term. Table 12-1 lists reasons for valve replacement in patients with IE.

Table 12-1. Infective endocarditis: major indications for surgery

Congestive Heart Failure
CHF accounts for more than 80% of valve replacements in IE. Most commonly, it is a complication of aortic valve endocarditis with resultant cusp perforation, but it may also occur in association with mitral valve infection. CHF may also occur as a result of myocardial abscesses, pericardial effusion, fistulae, and other hemodynamic complications of IE. Significant CHF (defined as that requiring more than minimal therapy) results in death in 50% to 90% of patients treated medically, whereas up to 60% survive with surgery. Patients with severe CHF resulting from valve perforation should undergo early valve replacement regardless of duration of antibiotic therapy or continued positive blood cultures. For patients with diseased mitral valves, recent studies suggest that valve repair rather than replacement offers a better clinical outcome. Patients who survive the procedure have a good prognosis. Persons with mild CHF may be treated medically with careful observation. Those with moderate CHF may have higher-than-expected death rates from coronary artery embolization. A common procedure at the time of valve replacement is to obtain a Gram’s stain and culture of the valve and possibly other removed tissues. A positive Gram’s stain is common and is related to the duration of antibiotic therapy. However, no relationship exists with outcome.
Infection with Resistant Organisms
Treatment of IE requires an effective bactericidal agent. Those most commonly employed are b-lactams, aminoglycosides, and vancomycin. Unusual cases of IE caused by organisms such as Chlamydia psittaci, Legionella pneumophila, Coxiella burnetii, and Brucella species may not be treatable with such compounds. Endocarditis caused by Pseudomonas aeruginosa or fungi should generally be managed with early surgical intervention. Although many cases of enteric gram-negative IE will require surgery, each case should be assessed individually. Patients should receive high-dose bactericidal agents, serum bactericidal levels should be monitored, and patients should undergo surgery if persistent bacteremia, CHF, or clinical deterioration occurs.
Extravalvular Extension of Infection
Extension of infection beyond the valve generally represents surgical disease and is best defined by TEE. Examples include (a) pericarditis, (b) valve ring abscess, (c) invasion of the conducting system, (d) myocardial abscess, and (e) fistulae. These complications occur most often in aortic valve disease. Clues include persistent fever, repeatedly positive blood cultures, pericarditis (although friction rubs are infrequently noted), and CHF not accounted for by overt valvular insufficiency. In unusual circumstances, cardiac catheterization can also be used to obtain quantitative blood cultures from different areas of the heart in an attempt to define the lesion anatomically.
Other Reasons for Operative Intervention
Embolization commonly complicates IE and can be associated with major morbidity and mortality. Recent data obtained from studies with 2-D echocardiography demonstrate that first embolic events occurred at a rate of more than 6/1,000 patient-days and did not depend on the presence of vegetations. Risk for emboli decreased with increased length of antimicrobial therapy. Classically, fungi and fastidious gram-negative organisms of the HACEK group (species of Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, Kingella) have been associated with large emboli. Recent data from echocardiography also suggest an enhanced likelihood of embolization from vegetations with viridans streptococci. Large emboli also may develop from atrial myxomas, which may be simultaneously infected. Valve replacement should be offered to patients who have had a second major embolus. However, a single embolic event plus echocardiographic evidence of a large (>1.5 to 2.0 cm) vegetation may also be an indication for surgery. Operative intervention based only on vegetation size is controversial. Several recent studies imply that patients with vegetations larger than 1.5 to 2.0 cm carry an excess risk for embolization and that surgery should be strongly considered on this basis alone. This may be especially true for disease on left-sided valves. It should be emphasized, however, that most vegetations are slow to resolve and will still be present at the end of therapy. A recent report demonstrated that echocardiographic persistence at the end of treatment is not an independent predictor of late sequelae.
Recent investigations have assessed the role of cardiac surgery in patients with cerebral embolization or other cerebrovascular complications. An intracerebral event was identified in about 10% of patients with IE, and overall mortality was 11%. An interval of 4 weeks between onset of cerebral complications and surgery is desirable.
Uncommonly, IE recurs following “adequate” antimicrobial therapy. This is usually secondary to localized or metastatic abscess or happens when infection has been associated with a more resistant organism. Consideration for heart surgery should be given if no remedial cause can be located in other areas. TEE and possibly cardiac catheterization should be undertaken to identify occult infectious foci.
Prosthetic Valve Endocarditis
Prosthetic valve endocarditis (PVE) complicates valve replacement surgery in 1% to 2% of cases. “Early” PVE occurs within the first 60 days, whereas the “late” type occurs thereafter. The former is associated with more aggressive pathogens and a less favorable prognosis. Pathologically, PVE usually involves infection around the valve ring with extension into adjacent myocardial tissue. This explains the poor results generally noted with medical therapy alone. Fever for more than 10 days following institution of antimicrobials portends extravalvular extension. Table 12-1 lists major reasons for cardiac surgery in PVE. Conditions already outlined for native valve IE also necessitate early operative intervention. These include (a) progressive or severe CHF, (b) recurrent major vessel embolization, (c) failure of appropriate medical therapy, and (d) IE caused by fungi and other resistant pathogens. Virtually all cases of early PVE fulfill these criteria, and surgery should generally be considered. Late PVE is a condition that closely mimics subacute native valve IE. Disease caused by nonstreptococcal organisms is statistically more likely to require valve replacement. A recent 20-year experience with late PVE demonstrated a 52% survivorship at 10 years. However, by the end of the study, only about 25% of patients were alive with the original prosthetic valve. (R.B.B.)
Bibliography
Abrams HB, et al. Is there a role for surgery in the acute management of infective endocarditis? A decision analysis and medical claims database approach. Med Decis Making 1988;8:165–174.
Report of a decision analysis to determine the best treatment for patients with left-sided Staphylococcus aureus infective endocarditis. Early surgery appeared to be associated with a longer life expectancy. Such data should be substantiated by prospective clinical studies.
Daniel WG, et al. Improvement in the diagnosis of abscesses associated with endocarditis by transesophageal echocardiography. N Engl J Med 1991;324:795–800.
This large investigation studied almost 120 patients with native or prosthetic valve endocarditis by M-mode, 2-D TTE, and TEE. Forty-six abscesses were identified from surgical or autopsy specimens. The aortic valve was the most common site of infection, and S. aureus was the most common pathogen. Mortality in patients with abscess was higher than in patients without this complication. TEE discovered 40 of 46, whereas TTE found only 13 of these (p <.001). It was concluded that TEE is more sensitive and specific for locating abscesses associated with infective endocarditis.
Dinubile MJ. Surgery in active endocarditis. Ann Intern Med 1982;96:650–659.
This exhaustive review summarizes the indications for surgery in native and prosthetic valve endocarditis. In addition to classic indications, the author summarizes information on the role of echocardiography and vegetation size in determining surgical need and provides tables of major and minor criteria for surgical intervention in active endocarditis.
Jault F, et al. Active native valve endocarditis: determinant of operative death and late mortality. Ann Thorac Surg 1997;63:1737–1741.
Records of approximately 250 patients who underwent surgery for active native valve IE were reviewed. Involvement of the aortic valve was most commonly noted. Operative mortality was approximately 8%. Risk factors for intraoperative death included advanced age and cardiogenic shock at time of surgery. Duration of antibiotic therapy did not influence surgical outcome. Long-term survival was worst with mitral valve IE and initial neurologic complications.
Mills SA. Surgical management of infective endocarditis. Ann Surg 1982;195:367–383.
This surgical review points out classic indications for surgical intervention in IE. These include congestive failure resulting from valve disruption, failure of antimicrobials, recurrent emboli, and paravalvular abscess. Major goals of surgery are removal of infected tissue and restoration of valve function.
Murphy JG, Foster-Smith K. Management of complications of infective endocarditis with emphasis on echocardiographic findings. Infect Dis Clin North Am 1993; 7:153–165.
This review summarizes data concerning the value of echocardiography, especially TEE, in the diagnosis and management of IE. Limitations of TEE are also presented.
Shively BK, et al. Diagnostic value of transesophageal compared with transthoracic echocardiography in infective endocarditis. J Am Coll Cardiol 1991;18:391–397.
These two modes of echocardiography were employed in 66 patients with suspected IE and compared with a gold standard. TEE was far more sensitive for defining the disease. Neither was associated with false-positive results.
Steckelberg JM, et al. Emboli in infective endocarditis: the prognostic value of echocardiography. Ann Intern Med 1991;114:635–640.
Patients with IE were identified within the first 72 hours of antimicrobial therapy and studied with 2-D echocardiography. First emboli were noted at a rate of 6.2/1,000 patient-days. Rates were similar in those with and without documented vegetations. Streptococcus viridans was associated with higher rates of embolization than S. aureus. Rates of embolization decreased with the length of antimicrobial therapy. Vegetations present by 2-D echocardiography did not appear to have an effect on the likelihood of embolization. S. viridans was associated with higher risks.
Tornos P, et al. Clinical outcome and long-term prognosis of late prosthetic valve endocarditis: a 20-year experience. Clin Infect Dis 1996;24:381–386.
The authors describe their experience with 59 patients with late prosthetic valve endocarditis followed for 20 years. Only about 25% remained alive and with their original valve. Mortality with other than streptococcal infection was significantly higher than that noted with streptococcal infection.
Vuille C, Nidorf M, Picard MH. Natural history of vegetations during successful medical treatment of endocarditis. Am Heart J 1994;128:1200–1209.
Echocardiography was employed to follow the natural history of vegetations during therapy for IE. At the time of termination of therapy, the majority of patients continued to have vegetations that were generally denser that those seen originally. Presence of vegetations was not an independent predictor of adverse outcome.

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