Patients who need surgery are often very sick and may be in CHF. For this reason and because they often require complex and long surgical procedures, myocardial protection is of utmost importance. Another important aspect of surgery for endocarditis is avoidance of contamination of the surgical field, instruments, drapes, and gloves with vegetations and pus. Instruments used to extirpate contaminated areas in the heart should be discarded before reconstruction of the ventricle and aortic root begins. In addition, local drapes, suction equipment, and surgical gloves should all be changed.
When the infection is limited to the cusps of the native aortic valve or a bioprosthetic valve, complete removal of the valve and implantation of a biologic or mechanical valve usually resolves the problem. There is no evidence that bioprostheses are better than mechanical valves in patients with active infective endocarditis.50 Some investigators believe that aortic valve homograft is ideal for patients with active endocarditis,51–53 but the fact is that it can become infected like other valves and there is no evidence that the risk of persistent or recurrent infection is different from other valves.54,55 Some surgeons favor the pulmonary autograft, particularly in young patients.56
If the aortic annulus is involved in the infective process, resection of the necrotic or inflamed area is needed before a prosthetic valve can be implanted. The defect created by the resection should be patched before a prosthetic valve is implanted. We prefer to use fresh autologous pericardium to patch small defects (1 or 2 cm wide) in the aortic root and left ventricular outflow tract (LVOT), and glutaraldehyde-fixed bovine pericardium for larger defects.57,58 Some surgeons also use Dacron fabric to reconstruct the aortic root.59,60 Here again, aortic valve homograft is believed to be ideal for reconstruction of the aortic root and LVOT.52,61–63 The mitral valve of the aortic valve homograft can be used to patch defects in the LVOT by correctly orienting the homograft. However, an aortic valve homograft is by no means a substitute for radical resection of all infected tissues, because persistent infection can occur with this biologic valve.64,65 The pulmonary autograft has also been used in cases of extensive destruction of the aortic root,66 but again, this valve is no substitute for radical resection of all infected tissues.
Surgery for aortic root abscess and/or cardiac fistulas is challenging. The most important aspect in the surgical treatment of these patients is radical resection of all infected tissues.25,55,57,58 We believe that the type of valve implanted is less important than complete extirpation of all infected and edematous tissues.58 These patients frequently require replacement of the entire aortic root and reconstruction of the surrounding structures that are also involved by the abscess. These operations must be individualized because the pathology of aortic root abscess is variable. Extensive resection and reconstruction may be needed.58,67–69 Thus, patching of the interventricular septum, dome of the left atrium, intervalvular fibrous body, right atrium, and pulmonary artery may be necessary, as well as repair of the left and/or right coronary arteries. The aortic root is often replaced with a valved conduit.
Aortic root abscess extending into the intervalvular fibrous body or into a prosthetic mitral valve is particularly difficult to treat.67–69 In these cases, the resection and reconstruction can be performed through the aortic root and dome of the atrium.67–69 When an aortic valve homograft is used for this type of reconstruction, the anterior leaflet of the mitral valve of the homograft can be used as patch material for the new fibrous body between the aortic and mitral valves. Actually, aortic and mitral valve homografts in a single bloc of tissue have been used to treat this condition.70
Postoperative complications are common after surgery for active infective endocarditis. Septic patients may have severe coagulopathy and may bleed excessively after cardiopulmonary bypass. Antifibrinolytic agents such as tranexaminic acid or aminocaproic acid should be used in addition to platelets, cryoprecipitate, and fresh-frozen plasma in patients with coagulopathy. The administration of recombinant Factor VII may also be necessary after correction of thrombocytopenia, fibrinogen level, and thromboplastin and prothrombin times. Radical resection of aortic root abscess may cause heart block, for which a permanent pacemaker will be needed postoperatively. Depending on the patient's clinical condition before surgery, multiorgan failure may develop postoperatively. Neurologic deterioration may occur in patients with preexisting cerebral emboli. Pulmonary, splenic, hepatic, and other metastatic abscesses seldom require surgical treatment. Large metastatic abscesses may have to be drained, and in the case of the spleen, splenectomy should be performed because of the risk of rupture.71
The prognosis of aortic valve endocarditis depends largely on when the disease is diagnosed, on the offending microorganism, and how promptly it is treated.30,31,72 Patients with prosthetic aortic valve endocarditis have a more serious prognosis than patients with native aortic valve endocarditis,31,36 and nosocomial infections are associated with higher mortality than community-acquired infections.73,74 The results of surgery for infective endocarditis have improved significantly since the introduction of antibiotics and surgery, but in-hospital mortality remains high at approximately 18%.31 Prosthetic valve endocarditis, increasing age, pulmonary edema, S. aureus infection, coagulase-negative staphylococcal infection, mitral valve vegetation, and paravalvular abscess were associated with an increased risk of in-hospital mortality at the ICE-PCS report on 2781 patients.31 Approximately one-half of those patients required surgery as part of their treatment.31
The operative mortality for patients with infection limited to the cusps of the aortic valve is largely dependent on the patients' clinical presentation at the time of surgery, age, and comorbidities. Most reports indicate that the operative mortality is under 10%.36,55,75 The operative mortality is higher for prosthetic valve endocarditis and ranges from 20 to 30%.25,26,31,76 Similarly, surgery for aortic root abscess is associated with higher operative mortality.58–63
We reviewed our 25-year experience with surgery for infective endocarditis in 383 consecutive patients.36 There were 226 patients with native and 117 with prosthetic valve endocarditis. The overall operative mortality was 12%. Preoperative shock, prosthetic valve endocarditis, paravalvular abscess and S. aureus were independent predictors of operative mortality. The 15-year survival for patients with native valve endocarditis was 59% and for patients with prosthetic valve endocarditis was 25% (p < .01). The freedom from recurrent infective endocarditis at 15 years was 86%, and similar for patients with native and prosthetic valve endocarditis. In most of these patients, a different microorganism caused the second episode of endocarditis.