Endocarditis

Introduction

• Endocarditis is an inflammation of the endocardium, the membrane lining the chambers of the heart and covering the cusps of the heart valves. Infective endocarditis (IE) refers to infection of the heart valves by microorganisms, primarily bacteria.
• Endocarditis is often referred to as either acute or subacute depending on the clinical presentation. Acute bacterial endocarditis is a fulminating infection associated with high fevers, systemic toxicity, and death within days to weeks if untreated. Subacute infectious endocarditis is a more indolent infection, usually occurring in a setting of prior valvular heart disease.

Clinical Presentation

General The clinical presentation of infective endocarditis is highly variable and nonspecific. Symptoms: Fever, chills, weakness, dyspnea, night sweats, weight loss, and/or malaise.

Signs: Fever is common, as well as a heart murmur (sometimes new or changing). The patient may or may not have embolic phenomenon, splenomegaly, or skin manifestations (e.g., Osler nodes or Janeway lesions).

Laboratory tests: White blood cell count may be normal or only slightly elevated. Nonspecific findings include anemia (normocytic or normochromic), thrombocytopenia, an elevated erythrocyte sedimentation rate or C-reactive protein, and altered urinary analysis (proteinuria/microscopic hematuria). The hallmark laboratory finding is continuous bacteremia; three sets of blood cultures should be collected over 24 hours. Other diagnostic tests An electrocardiogram, chest radiograph, and echocardiogram are commonly performed. Echocardiography to determine the presence of valvular vegetations plays a key role in the diagnosis of infective endocarditis; it should be performed in all suspected cases.

Treatment

• Goals of Treatment: relieve the signs and symptoms of disease. Decrease morbidity and mortality associated with infection. Eradicate the causative organism with minimal drug exposure. Provide cost-effective antimicrobial therapy. Prevent IE in high-risk patients with appropriate prophylactic antimicrobials.

NONPHARMACOLOGIC THERAPY

• Surgery is an important adjunct to management of endocarditis in certain patients. In most cases, valvectomy and valve replacement are performed to remove infected tissues and restore hemodynamic function. Indications for surgery include heart failure, persistent bacteremia, persistent vegetation, an increase in vegetation size, or recurrent emboli despite prolonged antibiotic treatment, valve dysfunction, paravalvular extension (eg, abscess), or endocarditis caused by resistant organisms.

Pharmacotherapy:

• Recommended therapy in the uncomplicated case caused by fully susceptible strains in native valves is 4 weeks of either high-dose penicillin G or ceftriaxone, or 2 weeks of combined or penicillin G or ceftriaxone therapy plus gentamicin
• For patients with complicated infection (eg, extracardiac foci) or when the organism is relatively resistant (MIC = 0.12–0.5 mcg/mL), combination therapy with an aminoglycoside and penicillin (higher dose) or ceftriaxone for the first 2 weeks is recommended followed by penicillin or ceftriaxone alone for an additional 2 weeks.
• The recommended therapy for patients with left-sided IE caused by methicillinsensitive S. aureus (MSSA) is 6 weeks of nafcillin or oxacillin, often combined with a short course of gentamicin
• For methicillin-resistant staphylococci (both MRSA and coagulase-negative staphylococci), vancomycin is used with rifampin for 6 weeks or more.