Infective endocarditis

History	Common causative organism
Native valve	Streptococcus viridans, Staphylococcus aureus
Prosthetic valve	Staphylococcus epidermidis
IVDA	Staphylococcus aureus

Presentation is nonspecific and variable, but the most common symptoms are fever and malaise.
The classic triad of fever, new heart murmur, and anemia is rare.
Patients may present acutely with critical illness, or subacutely with low-grade fever, fatigue, weight loss, and distal emboli.

Patients may present in acute or progressive congestive heart failure with dyspnea, frothy sputum, and chest pain. This is the most common complication.
The second most common complication is arterial embolization of valve vegetation fragments. These emboli can affect any body system:
- Central nervous system (CNS): cerebrovascular accidents (CVA), subarachnoid hemorrhage (SAH), acute monocular blindness.
- Renal: back pain, hematuria, renal failure.
- Pulmonary: pneumonia, infarction, pleural effusion.
- Gastrointestinal (GI): splenic infarction, mesenteric ischemia.
Heart blocks and arrhythmias are also possible as the infection may extend through the septum and into the cardiac conduction system.
Patients may present with respiratory compromise, diminished pulmonary capacity, altered mental status, or evidence of sepsis.

Definitive diagnosis is made by positive blood culture(s), and evidence of valvular injury or vegetations on echocardiogram.
Echocardiography should be performed as soon as possible.
A transesophageal echocardiogram is more sensitive and should be performed in patients with a high clinical suspicion and a normal transthoracic echocardiogram.
Nonspecific laboratory findings include leukocytosis, normocytic anemia, elevated C-reactive protein (CRP), elevated erythrocyte sedimentation rate (ESR), and hematuria.
There are no specific findings on ECG or chest radiography.
Other physical examination findings are due to circulating immune complexes that are embolizing (Table 56.2).
The Duke Criteria are widely used to diagnose infective endocarditis and have a sensitivity of about 90% (Table 56.3). A positive diagnosis consists of
- Two major criteria, or
- One major criterion and three minor criteria, or
- All five minor criteria.