Infective endocarditis means infection of the inner layer of the myocardial wall. This layer is known as endocardium and it consists of a thin membrane lining the atria, ventricles and heart valves. The endocarditis is usually caused by bacteria, especially from groups of streptococci and staphylococci. Rarely, it may be also caused by fungal infection.
The underlying cause of infective endocarditis is usually a combination of more risk factors named below.
The presence of bacteria within the heart
When bacteria enter the heart cavities, they get in a close contact with heart endocardium. And how do they get into the heart? The easiest way is with the blood that flows through the heart. It turned out that bacteria enter our bloodstream many times a day during various common everyday activities (e.g. when cleaning teeth, during defecation, etc.) and during many invasive medical procedures. However, our immune system is more than capable to get us rid of those unwelcomed guest. Increased risk of infective endocarditis is in people with weakened immunity and in people, whose circulatory system comes to a close direct contact with the environment (patients with central venous catheters, patients undergoing chronic dialysis, intravenous drugs users, etc.). Every injection can be dangerous without proper hygiene.
Disorders of endocardium and heart valves
There may be many endocardial disorders that can increase the risk of infective endocarditis. It includes heart valve diseases, congenital heart defects, presence of artificial valves and post-cardiosurgical states. In damaged or abnormal endocardium there is an increased risk of blood clot formation and such blood clots are a good environment for bacteria.
Combination of these two factors causes a real risk of infective endocarditis. When bacteria enter the bloodstream, and when our immune system can not stop them, they enter the heart and can colonize any blood clot occurring in the endocardium. Such infected blood clot is referred to as infectious vegetation.
The infectious vegetation can grow and narrow a valve causing resistance to the blood flow, or it can erode the valve tissue and cause its insufficiency. Both conditions can lead to symptoms of heart failure. In addition, small pieces of infectious vegetation can break off and travel with the blood stream to distant tissues and organs. These pieces are referred to as infectious emboli. They can damage distant tissues by local obstruction of small arteries and they can also become sources of further infection.
The symptoms of infective endocarditis can be acute or chronic; sometimes they are very indefinite and insidious. Infective endocarditis usually manifests with fever, general malaise, fatigue, loss of appetite and night sweats. The signs of heart failure may develop slowly or occur suddenly (shortness of breath, painful enlargement of the liver filled with blood, leg swelling, etc). Sometimes, the emergence of infectious vegetation on a heart valve may result in a heart murmur that can be heard when listening with a stethoscope.
The infectious emboli mentioned above can have many symptoms according to their presence. In brain they can cause classical ischemic stroke and due to bacterial presence, this can lead to occurrence of a brain abscess. Septic emboli can get into small blood vessels on the fingers and cause formation of small hemorrhages in then nail beds.
The best way how to confirm the infection is the echocardiography as it can found the vegetations affecting the endocardium. Transesophageal echocardiography is more efficient in diagnostics than the normal one. Samples of venous blood may be taken for a microbiological examination (so-called hemocultures) to determine the bacterial presence.
The prevention involves preventive administration of antibiotics before medical procedures that could cause bacterial penetration into the heart (such as pacemaker implantation, dental procedures, etc.). Of course, the majority of people do not receive the antibiotics; these are reserved for people with increased risk such as people with congenital heart defects, people with artificial heart valves, dialyzed patients and people who have already undergone infective endocarditis in the past.
Endocarditis is a dangerous disease and it must be treated during hospitalization with high doses of intravenous antibiotics for several weeks. The auxiliary therapy should focus on complications, especially signs of heart failure. If the conservative therapy is inefficient and the vegetations are too large, it is sometimes necessary to perform a cardiosurgical intervention with removal of the vegetations with the affected valve and replace it with an artificial one.