Infective endocarditis

Infective endocarditis occurs in cardiac conditions that result in turbulent blood flow and in association with a significant pressure gradient. An isolated secundum atrial septal defect (ASD), an example of a lesion without pressure gradient, does no increase the risk of endocarditis, as compared to individuals without structural heart disease. Patients with mitral valve prolapse and regurgitation are at increased risk for endocarditis.

Endocarditis should be suspected in any patient with unexplained fever and evidence of valvular or congenital heart disease. Various diagnostic criteria have been published, all of which are based on a combination of clinical features, blood cultures and echocardiography.

Four basic processes are responsible for the signs and symptoms of endocarditis and its complications. Damage to the valve, embolization, sustained bacteremia, that results in fever and multiple constitutional symptoms, and circulating immune complexes that result in vasculitis and glomerulonephritis.

Cardiovascular manifestatins of endocarditis include murmurs that are usually regurgitant and due to pre-existing structural heart disease or the destructive effects of the infection. Local myocardial abscess formation that may involve the valve ring or the interventricular septum, resulting in A-V conduction problems and fistulae. Mycotic aneurysms due to microbial invasion of the distal vasculature that may form anywhere in the arterial system and rupture with disastrous complications.