Bacterial Endocarditis

The presentation of bacterial endocarditis is classified as subacute or acute [1]. While both forms share similar features, they differ regarding duration and rate of progression.

Subacute

Patients with this type experience an insidious onset of nonspecific symptoms such as low-grade fever, fatigue, anorexia, weight loss, malaise, night sweats, chills, and arthralgia. These may persist for weeks to months [2].

Acute

The clinical picture of acute bacterial endocarditis consists of a sudden onset of fever [3] along with a rapid and aggressive course [4]. Septic shock may occur in these critically ill individuals. The majority of patients will have a heart murmur.

Complications

Patients with bacterial endocarditis are at risk for congestive heart failure (CHF), stroke, various types of infection [2], myocardial infarction, etc.

Physical exam

Up to half of all patients will exhibit classic physical signs such as 1) petechiae, 2) splinter hemorrhages, 3) Osler's nodes, 4) Janeway lesions and 5) Roth's spots. The latter three are considered minor criteria used for diagnosis of bacterial endocarditis [5].

Notable vital sign findings include fever and tachycardia. The patient overall appears toxic and pale. Also, patients with CHF present with jugular vein distension and peripheral edema. Moreover, focal neurologic deficits occur in up to 40% of affected patients [6]. Delirium and other mental status changes may be evident. Additionally, conjunctival hemorrhage may also be apparent.

The cardiac exam is a crucial component of the physical assessment as auscultation typically reveals the presence of a murmur. This may either be new or an exacerbation of a preexisting murmur. Other abnormal heart and lung sounds may include gallops, rales, pericardial rub, and pleural friction rub.

The clinical assessment should include a detailed history of the patient and the inquiry about risk factors such as congenital heart defects, history of the rheumatic disease, and the presence of prosthetic valves [7] as well as intravenous drug use (IVDU) [8].

The clinical presentation, history, and physical exam findings should raise suspicion for bacterial endocarditis. Further testing is necessary as described below. Also, the clinician must follow the Duke diagnostic criteria for endocarditis to establish the diagnosis [5].

Laboratory tests

The American Heart Association (AHA) recommends obtaining at least three blood cultures, of which the initial and final sets are drawn at least one hour apart [5]. Furthermore, the samples should be retrieved from 3 different venipuncture sites. Very importantly, initiation of empiric antibiotic treatment should be postponed until after cultures are provided.

The workup further includes a complete blood count (CBC), complete metabolic panel (CMP), erythrocyte sedimentation rate (ESR), complement panel, coagulation studies, and rheumatoid factor (RF). These tests may reveal leukocytosis, anemia, elevated ESR, and positive RF. Also, urinalysis typically shows microscopic hematuria and may also depict red blood cell (RBC) casts.

Imaging

The AHA also recommends the use of echocardiography to investigate the presence of valvular vegetations and annular abscess [5] and to evaluate the valvular and heart function overall. Specifically, transthoracic echocardiography (TTE) is the initial imaging modality performed in most individuals while transesophageal echocardiogram (TEE) is the study of choice for those with a cardiac implantable electronic device (CIED) [9] or prosthetic valves [5].

Note that a patient with manifestations suggestive of cerebral emboli should be evaluated with a head computed tomography (CT) scan [10] or magnetic resonance imaging (MRI) [5].

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8. Berlin JA, Abrutyn E, Strom BL, et al. Incidence of infective endocarditis in the Delaware Valley, 1988–1990. Am J Cardiol. 1995;76(12):933–6.
9. Baddour LM, Epstein AE, Erickson CC, et al. Update on cardiovascular implantable electronic device infections and their management: a scientific statement from the American Heart Association. Circulation. 2010;121(3):458-77.
10. Roe MT, Abramson MA, Li J, Heinle SK, et al. Clinical information determines the impact of transesophageal echocardiography on the diagnosis of infective endocarditis by the duke criteria. Am Heart J. 2000; 139(6):945-51.

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