Acute bacterial endocarditis usually begins suddenly with a high fever (102° to 104°F [38.9° to 40°C]), fast heart rate, fatigue, and rapid and extensive heart valve damage.
Subacute bacterial endocarditis may cause such symptoms as fatigue, mild fever (99° to 101° F [37.2° to 38.3°C]), a moderately fast heart rate, weight loss, sweating, and a low red blood cell count (anemia). These symptoms can be subtle and may occur for months before endocarditis results in blockage of an artery or damages heart valves and thus makes the diagnosis clear to doctors.
In both acute and subacute bacterial endocarditis, arteries may become blocked if accumulations of bacteria and blood clots on the valves (called vegetations) break loose (becoming emboli), travel through the bloodstream to other parts of the body, and lodge in an artery, blocking it. Sometimes blockage can have serious consequences. Blockage of an artery to the brain can cause a stroke, and blockage of an artery to the heart can cause a heart attack. Emboli can also cause an infection in the area in which they lodge and/or block small blood vessels and damage organs. Organs that are often affected include the lungs, kidneys, spleen, and brain. Emboli also often travel to the skin and back of the eye (retina). Collections of pus (abscesses) may develop at the base of infected heart valves or wherever infected emboli settle.
Heart valves may become perforated and may start to leak (causing regurgitation) — within a few days. Some people go into shock, and their kidneys and other organs stop functioning (a condition called septic shock). Infections in arteries can weaken artery walls, causing them to bulge or rupture. A rupture can be fatal, particularly if it occurs in the brain or near the heart.
Other symptoms of acute and subacute bacterial endocarditis may include
Painful nodules under the skin
Tiny reddish spots that resemble freckles may appear on the skin and in the whites of the eyes. Small streaks of red (called splinter hemorrhages) may appear under the fingernails. These spots and streaks are caused by tiny emboli that have broken off the heart valves. Larger emboli may cause stomach pain, blood in the urine, or pain or numbness in an arm or a leg as well as a heart attack or a stroke. Heart murmurs may develop, or preexisting ones may change. The spleen may enlarge.
Prosthetic valve endocarditis may be an acute or subacute infection. Compared with infection of a natural valve, infection of a replacement valve is more likely to spread to the heart muscle at the base of the valve and can loosen the attachment of the valve to the heart. Alternatively, the heart’s electrical conduction system may be interrupted, resulting in slowing of the heartbeat, which may lead to a sudden loss of consciousness or even death.