Infective endocarditis (IE) is a serious infection of the heart’s inner lining, the endocardium, often involving the heart valves. This infection arises when bacteria or fungi enter the bloodstream and attach to damaged heart tissue, forming growths called vegetations. These vegetations are collections of germs and debris that can disrupt normal heart function and lead to severe complications throughout the body. The disease can be lethal if not treated promptly with antibiotics, which may or may not be accompanied by surgery.
Cardiac Complications
Infective endocarditis causes damage within the heart. The vegetations can directly destroy heart valves. This destruction can lead to valvular insufficiency, where the valves leak blood backward, or stenosis, where they narrow and obstruct blood flow. Such damage often necessitates surgical intervention to repair or replace the affected valves.
Severe valvular damage or the spread of infection within the heart muscle can impair the heart’s pumping ability, leading to heart failure. Heart failure means the heart struggles to pump sufficient blood to meet the body’s demands, resulting in symptoms like shortness of breath and swelling.
Perivalvular abscesses, which are pockets of pus, can form around the heart valves or in adjacent heart tissue. These abscesses can disrupt the heart’s electrical system, potentially causing abnormal heart rhythms, or lead to the formation of fistulas, which are abnormal connections between heart chambers or blood vessels. Perivalvular abscesses are relatively common and are associated with increased illness and death rates.
Embolic Complications
Embolic complications occur when fragments of vegetations detach and travel through the bloodstream. These fragments, called emboli, can block blood vessels, leading to tissue damage or infarction in various organs. Systemic embolization is a common occurrence in patients with infective endocarditis.
When emboli reach the brain, they can cause ischemic strokes, which are blockages of blood supply to brain tissue. Neurological complications, including strokes, develop in patients with infective endocarditis and represent serious complications. Symptoms can vary depending on the affected brain area but may include sudden weakness, numbness, or difficulty speaking.
Emboli can also travel to the spleen, leading to splenic infarction, which is the death of spleen tissue due to lack of blood flow, or the formation of splenic abscesses. Renal emboli can block renal arteries, causing kidney damage known as renal infarction. These blockages can impair organ function and may require medical intervention.
Emboli can also travel to arteries in the limbs, potentially causing limb ischemia, characterized by pain, numbness, and tissue death. In severe cases, this can lead to gangrene and may necessitate amputation. If the infection is located on the right side of the heart, emboli can travel to the lungs, causing pulmonary embolism, a blockage in the lung arteries.
Systemic Infection and Abscess Formation
Beyond cardiac damage and embolic events, infective endocarditis can spread, forming new infection sites or affecting blood vessels. Brain abscesses, distinct from embolic strokes, are collections of pus that form within the brain tissue due to the direct spread of bacteria. These can cause neurological symptoms and require prompt treatment.
Mycotic aneurysms are a serious complication, involving weakened and bulging areas in blood vessel walls caused by bacterial infection. These infected aneurysms can rupture, leading to severe bleeding, particularly when they occur in the brain.
The bacteria from the heart can also spread through the bloodstream to bones, causing osteomyelitis, or to joints, leading to septic arthritis. These skeletal and joint infections can cause pain, swelling, and long-term damage to the affected areas. Other organs, such as the liver or kidneys, can also develop abscesses as a result of the bacteria spreading through the blood.
Immune-Mediated Complications
The body’s immune response to the ongoing infection in infective endocarditis can also lead to complications, even without direct bacterial invasion or emboli. Glomerulonephritis is an inflammation of the kidney’s tiny filtering units. This condition occurs when immune complexes, which are formations of antibodies and bacterial antigens, deposit in the kidneys, impairing their ability to filter waste from the blood and leading to kidney dysfunction.
Vasculitis, which is the inflammation of blood vessels, can also occur as an immune-mediated complication. It can affect various blood vessels throughout the body, potentially leading to a range of symptoms depending on the vessels involved. The immune system’s sustained activation can also manifest as other systemic signs.
These can include general signs like arthritis, causing joint pain and swelling, or specific skin lesions. Examples include Janeway lesions, which are painless red spots on the palms and soles, and Osler’s nodes, which are tender red or purple bumps on the fingers or toes. These manifestations are often a result of the body’s immune reaction to the persistent infection rather than direct bacterial presence.