Bacterial endocarditis is an inflammation of the inner layer of the heart caused by bacteria. It most commonly affects the heart valves (either native or prosthetic). Apart from heart valves endocarditis may affect the interventricular septum, the chordae tendinae, the mural endocardium and in some cases intracardiac devices. In endocarditis there is a formation of a specific prototypic lesion, the vegetation made of a mass of platelets, fibrin, microcolonies of microorganisms and scant inflammatory cells. In case of subacute form of endocarditis the center of the vegetation is in a form of granulomatous tissue that may undergo fibrosis or calcification.
Endocarditis in general can be classified into infective and non-infective. Bacterial endocarditis is a form of infective endocarditis.
Clinical Characteristics of Acute Bacterial Endocarditis
Bacteria endocarditis develops as a consequence of bacteriemia and there is a local invasion of these organisms, peripheral embolization and formation of immune complexes. Patients suffering from bacterial endocarditis may develop numerous non-specific symptoms. Still, almost 99% of all patients develop increased body temperature. It is essential to pay special attention to patients who are already suffering from congenital heart diseases. Additional symptoms and signs of bacterial endocarditis include chills, sweats, malaise, cough, headache, myalgia, arthralgia and confusion.The condition develops in a form of acute, toxic and febrile illness and the symptoms last for less than 2 weeks. In majority of cases infection is caused by Staphylococcus aureus.
Diagnosing Acute Bacterial Endocarditis
The diagnosis of acute bacterial endocarditis is set according to the Duke criteria and is based on specific pathologic as well as clinical findings. Pathologic criteria include the presence of microorganisms on cultures or histological conformation of active disease in the vegetation or tissue obtained from intracardial abscess. Clinical criteria that are taken into consideration when it comes to diagnosing bacterial endocarditis are classified as major and minor. Major criteria include positive blood cultures or persistently positive blood cultures (the precise infective agent is identified) and positive echocardiography findings such as oscillating mass and/or vegetation, paravalvular abscess or dehiscence of a prosthetic valve. Another major criteria is new valvular regurgitation. Minor criteria include predisposition (for example history of IV use or congenital heart disease), fever with temperature of more than 38°C, vascular phenomena such as arterial emboli, septic pulmonary infarcts etc., immunologic phenomena (glomerulonephritis, Osler nodes, Roth spots etc.) and positive blood culture findings.
Treatment for Acute Bacterial Endocarditis
Acute bacterial endocarditis is treated with a high dose of antibiotics. These medications are administered intravenously. This way the effects of the treatment are much better. The patient receives antibiotics for a longer period of time (2-6 weeks). Surgical debridement of infected material and replacement of the valve with an artificial valve is only performed in patients who have not managed to fight microorganisms and whose valves are seriously damaged by the infection. Surgery is also performed on patients with unstable prosthetic valve or obstruction, recurrent septic emboli, early closure of mitral valve, gram negative species, large vegetations and abscess formation.