EARLY INFECTIVE ENDOCARDITIS ON PROSTHETIC VALVES

Despite major advances in cardiovascular surgical techniques and routine use of prophylactic antimicrobial agents, prosthetic valve endocarditis (PVE) continues to complicate the course of a small percentage of patients after cardiac valve replacement. Using actuarial methods to describe the risk of PVE after valve implementation, several studies have shown that its incidence peaked at around 5 weeks and levelled off to a stable rate by 12 months, for a cumulative risk of 3% at that time. The microbial aetiology of early PVE is dominated by staphylococcal species, S. epidermis and S. aureus accounting for about 30% and 20% of cases, respectively, even though prophylactic regimens wed today are targeted against these microorganisms. In nearly all patients, infection spread behind the site of attachment of the valve prosthesis, resulting in valve ring abscesses and valve dehiscence in 60% of cases. valve obstruction by vegetations is much more uncommon except in patients with mitral or tricuspid valve endocarditis. The clinical course of early PVE tends to be frequently fulminant, with rapid deterioration of the haemodynamic status due to valvular or annular destruction or persistent bacteraemia. In some cases, however, the classic symptoms of endocarditis may be less noticeable because signs related to an initial source of bactria, such as sternotomy wound infection, may be more prominent While various non-invasive and invasive studies have been proposed to aid in the diagnosis of PVE, transoesophageal echocardiography is now the technique of choice for that purpose, as well as for detecting prosthetic valve dysfunction and other intracardiac complications of PVE. The overall mortality of early PVE remains very high, ranging from 40 to 60%. In many patients, surgical approach may offer the only possibility to stabilize cardiac haemodynamics, to eradicate the infection, and to reduce the mortality.