Indications and Evaluation for Surgery

Generally speaking, major absolute indications for surgical intervention in IE include—

1. hemodynamic compromise,

2. persistent and/or uncontrolled infection despite aggressive medical therapy, and

Significant anatomical changes and complications caused by IE, such as aneurysm, fistula, and atrioventricular discontinuity, may also be considered an indication, as they usually indicate the imminent occurrence of hemodynamic compromise. Some authors have advocated other relative indications for surgery (Table 8.1) [2,5,11]. The most common indication for surgery is usually heart failure, followed by persistent sepsis [2,9,12].

Surgical outcomes are better in healed IE operations than in acute IE surgeries. However, in the presence of a major indication, or when clinical judgment strongly suggests that surgical indication is imminent, there should be no delay in carrying out the operation, even with active IE. Hemodynamic stability takes priority over infection control by medical treatment.

Table 8.1. Indications for Surgery in IE

Absolute indications

Hemodynamic compromise due to valvular dysfunction Uncontrolled infection despite appropriate antimicrobial treatment

Fungal endocarditis with vegetations Embolic event (cerebral or peripheral) Recurrent embolization Emboli after adequate antibiotic therapy Anatomical complications/deformities Abscess Fistula

Aneurysm/pseudoaneurysm Aortoventricular/atrioventricular discontinuity Valve dehiscence and paravalvular leak (in PVE)

Relative indications

Echocardiographic detection of—

Large vegetations (>10 mm in diameter) Vegetations increasing in size after 4 weeks of antimicrobial therapy New conduction blocks

When to operate for IE remains a controversial issue and is often addressed on a case by case basis. Surgical timing strategies have evolved considerably over the recent years, owing to the developments in the medical management of infectious diseases and in diagnostic tools, echocardiography in particular. The more routine use of TEE, beginning in the 1990s, has especially led to earlier and more accurate identification of surgical indications and more optimal timing of operation.

Early diagnosis by echocardiography and blood cultures, identification of the causative microorganisms, detection of localized foci of infection by advanced imaging techniques, and availability of more effective antimicrobials have all definitely changed the decision-making process and timing for surgery. Such improvements have even enhanced the frequency of successful medical management without the immediate need for cardiac surgery. On the other hand, improvements in operative techniques, postoperative care, availability and quality of prosthetic valves, and the accuracy in early prediction of inevitable surgery are all in favor of earlier surgical intervention. Many situations that were once considered high-risk for surgery have demonstrated better outcomes with surgical intervention than with conservative medical management.

Significant acute aortic or mitral regurgitation with heart failure in the setting of NVE is an obvious indication for surgery. Some authors have also advocated the following findings as indications for surgery: large vegetations [2,11], especially those that are >10 mm in diameter [13]; increase in the size of vegetations after adequate antimicrobial therapy [5]; and the presence of vegetations in the setting of a fungal IE [5], since antifungal penetration into vegetations is not adequate for cure. Detection of vegetations following an embolic event may require urgent surgery, if further embolic episodes are deemed imminent.

In the absence of severe valvular dysfunction, surgical timing will be influenced by TEE information demonstrating the anatomy and function of the valves, perivalvular structures, and possible extension of the infectious process to the annular and/or muscular structures. Although some cases of perivalvular abscess can be successfully treated medically, the presence of annular/perivalvular abscesses indicates surgery [14]. Even with controlled infection and stable hemodynamic situation, perivalvular abscess constitutes a risk factor for more serious complications and recurrent IE, and perivalvu-lar abnormalities are common despite early surgical intervention [14,15]. Abscesses are commonly associated with pseudoaneurysm and/or fistula formation. If echocardiography is not conclusive with regard to abscess presence or extension, the patient should be followed closely with serial echocardiographic studies. Abscesses are found more often in aortic IE, but have a higher incidence of pseudoaneurysm/fis-tula formation in the mitral position [16]. Septal abscesses associated with aortic IE may cause conduction abnormalities. Indeed, a new conduction block on ECG in the setting of IE has a high positive predictive value for the presence of perivalvular abscess [17].

In cases of PVE, surgical indications would include all of the aforementioned plus prosthesis dehiscence and new/dynamic paravalvular leak as documented by serial echocardiography. Increasing paravalvular leak is an ominous sign of circumferential extension of dehiscence and should lead to consideration of more aggressive treatment including surgery.

A complication of the infectious process that mandates careful evaluation is systemic embolization, a cardinal determinant of mortality and morbidity in IE patients. Embolic events are reported in up to half of IE cases [5]. Of these, up to 71% are cerebral embolic events [18]. Most embolic events occur within two weeks of onset of symptoms [18] or initiating antibiotic ther apy [19]. Therefore, the greatest impact of surgical intervention on the incidence of emboli is within these time limits. An embolic event during the first two weeks of antimicrobial therapy or recurrent embolism at any time should indicate surgery [8]. A detailed discussion on strategies to prevent embolism is presented in Chapter 13.

A major issue in the timing of surgery is the presence of a cerebral infarct. Because of the risks imposed by anticoagulation and the potential risk of cerebral edema due to car-diopulmonary bypass, it is generally agreed that hemorrhagic cerebral infarct is a contraindication to surgery, at least temporarily. The main controversy arises on the timing of surgery with non-hemorrhagic infarcts due to their potential for hemorrhagic transformation. Some investigators have demonstrated better outcomes when surgery is performed at least 11 days after ischemic and 23 days after hemorrhagic cerebrovascular accident [20]. Others have reported considerably more favorable outcomes even when cardiac surgery is performed within 72 hours of cerebrovascular accidents as opposed to deferring operation after eight days [18]. Our practice and recommendation is to defer the operation for at least two weeks after a non-hemorrhagic stroke and four weeks after a hemorrhagic episode [21].

In some patients, symptomatic embolic CVAs may be followed by the detection of intracranial mycotic aneurysms, the rupture of which can cause catastrophic results [5]. Although uncommon, these aneurysms can sometimes leak slowly, and anticoagulation for cardio-pulmonary bypass can predispose these patients to a potentially fatal hemorrhage. Careful imaging studies prior to cardiac surgery should therefore be undertaken if there is any clinical suggestion of a possible intracranial mycotic aneurysms.

Splenic abscess (or abscess located elsewhere) is another complication of the infectious process in IE that may cause persistent bacteremia/sep-sis. It does not usually respond well to antibiotic therapy and should be treated surgically, by splenectomy (or surgical drainage and debride-ment in other locations), or drained percuta-neously before valve surgery is performed. In general, every attempt is made to eradicate any identified source of infection before cardiac surgery for IE is performed to prevent recurrence.

Both cranial and abdominal computed tomography should be considered in all patients with IE to assess for the presence of any abscess, infarct, hemorrhage, or aneurysm.

Finally, like any other open-heart surgery, the patient should also be evaluated from other cardiac and non-cardiac standpoints. Hepatic and renal functions are of particular importance, as they have a great impact on the surgical outcomes. Unjustified delay of the operation, when surgery is indicated, may cause deterioration in renal and/or hepatic function due to both the disease itself and the toxicity of medications, antibiotics in particular.

This underscores, once again, the significance of the right timing for surgery. Comorbidities (diabetes, etc.) should be considered and properly addressed. In patients with a high risk of coronary artery disease, preoperative angiogra-phy should be performed to assess for the possible need of coronary artery bypass grafting at the same operative session.

In view of the fact that cardiac surgery is an integral part of IE management, early consultation with the cardiac surgery team is strongly recommended following the diagnosis of IE. This will allow the surgical team to be fully familiar with the patient, in case surgery is eventually needed. It will also enable medical and surgical teams to join forces in determining the need and optimum timing for surgery. The American College of Cardiology/American Heart Association Guidelines for the Management of Patients with Valvular Heart Disease also support early surgical consultation in IE cases [22].

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