What is Infective Endocarditis?
Infective endocarditis is an infection that establishes itself on the inner surfaces of the heart. This critical internal layer, called the endocardium, provides the lining for the heart chambers and covers the heart valves. The disease begins when microorganisms, typically bacteria, enter the bloodstream and attach to these surfaces.
The hallmark of this condition is the formation of infectious masses known as vegetations. These are clumps composed of the invading microbes mixed with blood cells like platelets and fibrin. The presence of these vegetations directly threatens the structural integrity of the heart valves, which can prevent them from opening and closing correctly and lead to severe damage.
Causes:Infective endocarditis is triggered by a specific sequence of events that allows microorganisms from another part of the body to enter the bloodstream and establish a colony inside the heart. The process is driven by the following critical factors:
- Breach of Bodily Defenses (Bacteremia): The process begins when bacteria or other microbes breach the body's natural barriers and enter the circulatory system. Common entry points include the gums during dental procedures, breaks in the skin from cuts or the use of intravenous catheters, or through the intestinal wall.
- Creation of an Adherent Surface: For the circulating microbes to colonize the heart, they need a suitable surface to latch onto. This is often created by pre-existing damage to the endocardium, turbulent blood flow caused by a structural heart defect, or the presence of a foreign object like an artificial heart valve, which provides an ideal anchor point.
- Formation of Infectious Vegetations: Once bacteria adhere to a susceptible area on the heart lining or valve, they begin to multiply. The body's clotting system responds by depositing platelets and fibrin over the bacteria, inadvertently creating a protective biofilm. This combination of microbes and blood components forms a mass known as a vegetation.
While a bloodstream infection can theoretically lead to endocarditis in anyone, the actual risk is vastly higher for individuals whose hearts are already structurally vulnerable. The following conditions and factors create a predisposition for this dangerous infection:
- The Presence of Artificial Heart Valves: Individuals with prosthetic heart valves, whether mechanical or made from biological tissue, are at a significantly elevated risk. These non-native surfaces are particularly susceptible to bacterial colonization.
- A History of Previous Endocarditis: A prior episode of infective endocarditis permanently damages the heart's inner lining, leaving scarred tissue that is more prone to future infections.
- Specific Congenital Heart Defects: People born with certain structural abnormalities of the heart have an increased lifelong risk. These defects can cause turbulent blood flow that erodes the endocardium, creating rough patches where bacteria can attach.
- Damaged Heart Valves (Valvulopathy): Any condition that has damaged the heart valves, such as rheumatic fever or age-related calcium deposits, makes them more likely to become infected.
- Intravenous Drug Use: The use of non-sterile needles to inject illicit drugs is a major risk factor, as this practice directly introduces bacteria from the skin and other sources into the bloodstream.
