Infective endocarditis represents the infection of the endocardium, most commonly that of the valves or congenital heart defects, but the mural area, prosthetic valves or implantable devices may also be involved. Acute bacterial endocarditis usually has a fulminant course and leads to death if left untreated, whereas the subacute variant has a slower progression, leading to a variety of clinical signs. The most frequent bacterial etiologic agents of acute endocarditis are enterococci. The emergence of multi-drug resistant strains make treatment more difficult and prognosis more grim.
Acute bacterial endocarditis patients are usually severely ill, with high fever, chills, poor appetite, weight loss and possible signs of embolism, acute heart failure or heart block. These may be patients who have previously been diagnosed with a congenital heart disease, individuals who recently underwent various procedures that can cause bacteremia or in whom bacteremia is the primary source. Fever may be absent in elderly or immunocompromised patients .
Clinical examination must be carefully performed and special attention must be paid to new murmurs or to a change in character of preexisting murmurs, suggestive of valvular dysfunction . However, murmurs are absent in about 33% of acute bacterial endocarditis cases. Heart rate evaluation is also important because intramyocardial abscesses, especially those originating from the aortic valve , can involve the conduction system and cause heart block . The patient may also exhibit acute heart failure symptoms , as well as signs of peripheral embolic phenomena, located in the central nervous system, lungs, kidneys, liver and spleen  Anterior mitral leaflet vegetations, especially if large and friable, are most likely to embolize , but the risk decreases after antibiotic treatment begins. Pulmonary embolism presents with chest pain, acute dyspnea and cough.
Peripheral signs of acute bacterial endocarditis are represented by Janeway lesions, located on the palms and soles and caused by vasculitis. The patient may also have articular or osseous pain, due to septic arthritis or osteomyelitis (most often vertebral). If consciousness level is decreased, the physician should suspect acute stroke or meningitis, that is usually purulent in acute endocarditis . If an implantable device is present, it requires special attention . Macroscopic hematuria may signify the presence of glomerulonephritis or embolic renal infarction.
While evaluating an acute bacterial endocarditis patient, all efforts should be made to identify the etiological agent. A minimum of three blood cultures should be obtained, preferably while the patient is febrile. Blood workup should also include determination of the inflammatory markers and rheumatoid factor. Leukocytosis is usually present. Baseline workup should also include creatinine, urea, blood urea nitrogen, glycemia, and electrolytes.,
The electrocardiogram is able to highlight rhythm and conduction abnormalities if present. The chest radiography is used to mark out concomitant pulmonary infection or pulmonary embolic pyogenic abscesses.
The definitive diagnosis is established following echocardiography, both transthoracic and transesophageal if needed . Emphysema, obesity and valve prosthesis make transthoracic diagnosis more difficult . A vegetation is described as an oscillating mass, usually attached to a valve, but may also be appended to implanted material or ventricular wall. This method is able to describe the size, motility, and consequences of the pathological process, such as leaflet perforation or pillar rupture, dehiscence of a prosthetic valve , abscess , aneurysm or fistula formation .
Computer tomography and magnetic resonance imaging are adjunct methods for acute bacterial endocarditis diagnosis, not widely used in clinical practice, except for selected cases .