The lesions of infective endocarditis are infected vegetations which usually develop on a pre-existing congenital or acquired cardiac lesion where blood is abnormally turbulent. Platelets and fibrin are deposited and can be invaded by circulating micro-organisms. Turbulence and pressure are related so that mitral and aortic valves are more often infected than are pulmonary or tricuspid valves (although lesions of the tricuspid are increasing owing to illicit drug administration), and ventricular rather than atrial septal defects. Predisposing valve lesions are usually a consequence of rheumatic heart disease but in addition valves which were previously normal or only slightly abnormal (bicuspid aortic valve, mitral valve prolapse) can become infected. Undiagnosed patent ductus arteriosus or aortic coarctation can also be involved. As the population grows older, infections on degenerate aortic valves are more often found and endocarditis on prosthetic valves is also more frequent. This is not due to an increase in the percentage of valves becoming infected but to an increasing number of surgically treated patients at risk.
KeywordsInfective Endocarditis Patent Ductus Arteriosus Positive Blood Culture Prosthetic Valve Bicuspid Aortic Valve
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