What is Infective Endocarditis?
Infective Endocarditis (IE) is an infection of the endocardial surface of the heart, including the heart valves. It is typically caused by bacteria, though fungi and other microorganisms can also be culprits. This infection can lead to serious complications if not treated promptly.
Histopathological Features
Histologically, IE is characterized by the presence of
vegetations on the heart valves. These vegetations are aggregates of fibrin, platelets, microorganisms, and inflammatory cells. They can lead to valve destruction and a range of other complications. The vegetations in IE are often friable and can break off, leading to systemic emboli.
Types of Infective Endocarditis
IE can be classified into two main types: acute and subacute. Acute IE is typically caused by highly virulent organisms like
Staphylococcus aureus and progresses rapidly. In contrast, subacute IE is generally caused by less virulent organisms, such as
Streptococcus viridans, and has a more insidious onset.
Pathophysiology
The pathogenesis of IE involves the adherence of microorganisms to the endocardial surface, followed by the formation of vegetations. The initial damage to the endocardium can be due to trauma, congenital heart defects, or other factors. Once the endocardium is damaged, microorganisms in the bloodstream adhere to the exposed subendothelial tissue, leading to the formation of vegetations.Microscopic Examination
Under the microscope, vegetations are seen as masses of fibrin and platelets interspersed with colonies of bacteria. Special stains, such as the
Gram stain, can be used to identify the bacterial species. The inflammatory response in the surrounding tissue can range from acute inflammation with neutrophils to chronic inflammation with lymphocytes and macrophages.
Complications
IE can lead to numerous complications, including valve destruction, abscess formation, and systemic embolization. Emboli can cause infarctions in various organs, leading to phenomena such as
Janeway lesions and
Osler nodes. The histological examination of affected organs can reveal microabscesses and infarcts caused by emboli.
Diagnosis
The diagnosis of IE is based on a combination of clinical, microbiological, and histological criteria. Blood cultures are essential for identifying the causative organism. Echocardiography can visualize vegetations and assess the extent of valve damage. Histologically, samples from valve resections or biopsy can confirm the presence of vegetations and identify the microorganisms involved.Treatment
The treatment of IE involves prolonged courses of antibiotics to eradicate the infection. In some cases, surgical intervention may be necessary to repair or replace damaged valves. Histological examination of resected valves can provide valuable information about the extent of infection and guide further treatment.Prevention
Preventive measures include prophylactic antibiotics for high-risk individuals undergoing certain medical or dental procedures. Maintaining good oral hygiene and managing predisposing conditions, such as congenital heart defects, can also reduce the risk of IE.
