Prosthetic Heart Valves

4.1. Epidemiology and Microbiology

The accumulative rate of prosthetic valve endocarditis (PVE) is 1.5-3% within 1 yr after valve surgery. This increases to 5.7% after 5 yr (17). Coagulase-negative staphylo-cocci are the predominant agent of PVE during the initial 2 mo of surgery and, in fact, are the most common organisms throughout the first year after a valve replacement. Thereafter, viridans streptococci, enterococci, S. aureus, and fastidious Gram-negative coccobacilli increase in prevalence. Gram-negative bacilli and fungal etiologies of prosthetic valve endocarditis are most common in the initial 2 mo after surgery.

4.2. Clinical Manifestation

The clinical features of PVE are similar to those of native valve endocarditis except that new murmurs are more frequent among those infected with prosthetic valves. Patients with PVE may develop congestive heart failure and systemic emboli. These symptoms are common in the general elderly population but should alert the clinician to the possibility of PVE. Any prolonged fever in a patient with a prosthetic valve should be viewed as possible PVE (17,18). Elderly patients often have less pronounced clinical symptoms than younger patients.

4.3. Diagnosis and Microbiology

The new Duke criteria enable the clinician to make the diagnosis of infective endocarditis more accurately (19). Definite diagnosis of infective endocarditis can be made by pathological criteria. (See chapter, "Infective Endocarditis," Tables 2 and 3.)

The use of transesophageal echocardiograms (TEE) has greatly improved the diagnosis of both native valve and prosthetic valve endocarditis. Kemp and colleagues

Table 3

Indications for Transesophageal Echocardiography for Suspected Infective Endocarditis

Prosthetic cardiac valves Left-sided infective endocarditis (IE) S. aureus IE Fungal IE Previous IE

Prolonged clinical symptoms (3 mo) consistent with IE Cyanotic congenital heart disease Patients with systemic to pulmonary shunts Poor clinical response to antimicrobial therapy for IE

reviewed the use of TEE in diagnosing PVE and found a range of sensitivity from 77-100%, and a negative predictive value of 90% (20). Table 3 illustrates conditions for which TEE might be especially helpful diagnostically.

4.4. Treatment

Treatment for PVE often involves prolonged therapy (Table 4) (17,21). In elderly patients who are taking coumadin, there may be drug interactions with rifampin. Also, nephrotoxicity with gentamicin is increased in the elderly and in patients taking concurrent nephrotoxins. Guidelines for therapy for infective endocarditis may be found on the Internet at http://www.americanheart.org. As many as 65% of patients with PVE may be candidates for surgical valve replacement (22,23). The need for cardiac surgery is increased in patients who have moderate to severe heart failure due to dysfunction of the prosthesis. Uncontrolled bacteremia, fever persisting for more than 10 d during appropriate antibiotic therapy, recurrent arterial emboli, and relapse after appropriate antimicrobial therapy are other indications for surgery. In addition, infections caused by fungi, S. aureus and Gram-negative bacteria often require surgical intervention.

4.5. Prevention

Prosthetic valves may become infected because of bacteremia resulting from invasive procedures (24). Elderly patients often have dental, gastrointestinal (GI), or genitourinary (GU) procedures that may cause a transient bacteremia. Table 5 reviews the dental procedures for which endocarditis prophylaxis including PVE is recommended. The indications for endocarditis prophylaxis for GI procedures are noted in Table 6 and the indications for PVE prophylaxis for GU (and respiratory) procedures are noted in Table 7. Note that prophylaxis is considered "optional" for some procedures but might be useful for high-risk patients such as those with prosthetic valves, a previous history of infective endocarditis, cyanotic congenital heart disease, ventricular septal defect, aortic valve disease, and mitral regurgitation. Moderate-risk cardiac conditions include mitral valve prolapse with regurgitation, tricuspid valve disease, mitral stenosis, and degenerative valve disease of the elderly. The regimens used for prophylaxis for patient allergic to penicillin may include clindamycin or azithromycin. (See chapter "Infective Endocarditis," Tables 5-7 [this chapter] for specific antibiotic regimens for oral and respiratory tract, and gastrointestinal and genitourinary tracts procedures, respectively).

Table 4

Prosthetic Valve Endocarditis Treatment

Streptococci

Highly penicillin-susceptible viridans streptococci or S. bovis (MIC s 0.1 ^g/mL) In patients whose infection involves prosthetic valves or other prosthetic materials, a 6-wk regimen of penicillins recommended together with gentamicin for at least the first 2 wk.

Streptococci with an MIC >0.1 ^g/mL

It may be desirable to administer the aminoglycoside for more than 2 wk (4-6 wk). Vancomycin can be used in penicillin allergic patients

Enterococci and nutritionally variant streptococci

Ampicillin or vancomycin plus gentamicin or streptomycin for 6-8 wk.

Methicillin-sensitive S. aureus

Nafcillin (or a first-generation cephalosporin or vancomycin if allergic) plus rifampin for 6 wk plus gentamicin for 2 wk. Rifampin plays a unique role in the eradication of staphylococcal infection involving prosthetic material; combination therapy is essential to prevent emergence of rifampin resistance

Methicillin-resistant S. aureus

Vancomycin plus rifampin for 6 wk plus gentamicin for 2 wk

Coagulase-negative staphylococci

Vancomycin plus rifampin for 6 wk plus gentamicin for 2 wk

HACEK

Third-generation cephalosporin for 6 wk Ampicillin plus gentamicin for 6 wk

For culture-negative or empiric treatment

Vancomycin plus gentamicin plus ceftriaxone or ampicillin-sulbactam plus gentamicin

MIC, minimum inhibitory concentration; HACEK, Haemophilus spp., Actinobacillus actinomycetam-comitans, Cardiobacterium hominis, Eikenella spp., Kingella kingae.

Your Heart and Nutrition

Your Heart and Nutrition

Prevention is better than a cure. Learn how to cherish your heart by taking the necessary means to keep it pumping healthily and steadily through your life.

Get My Free Ebook


Post a comment