The heart, a four-chambered muscular organ, that indefatigably pumps blood to the entire throughout life can also get infected and inflamed. Infections in the heart pose a more challenging clinical situation. Prompt treatment and prevention of further episodes are essential to keep the heart in good health.
Bacterial endocarditis (BE) is an inflammation of the heart valves and the innermost lining of the heart called the endocardium. In addition, the septae that separate the chambers of the heart and the chordae tendineae (fibrous supports that enable the opening and closing of the valves) may be inflamed. The inflammation occurs due to infection with microorganisms called bacteria.
An inflammation that may occur suddenly, called acute bacterial endocarditis, is caused by a bacterium called staphylococci. At other times, the inflammation may have a slower onset and a longer course, called subacute endocarditis, which is caused by viridans streptococci, enterococci, and coagulase negative staphylococci.
Bacterial endocarditis typically occurs in people who have defective heart valves. The heart valves may be defective since birth (congenital defects) or may have been damaged due to diseases like a heart attack or rheumatic heart disease later in life.
Any implanted devices like an artificial valve or pacemaker implanted to replace the defective natural ones pose a higher risk for bacterial endocarditis. A tubing or catheter left in the blood vessels for long periods allow entry of bacteria into the bloodstream and hence cause endocarditis. Drug abusers who inject drugs into the blood vessels are similarly at high risk.
Dental and medical procedures can increase the risk for BE. The causative bacteria like the Streptococcus viridans are a part of the resident flora in the crevices between teeth and the skin. Any procedures done on teeth or in the urinary system or digestive tract allow invasion into the bloodstream due to exposure of blood vessels during these procedures.
Teeth that are in poor health and hygiene when brushed vigorously enough to cause micro abrasions or bleeding, can lead to invasion of bacteria into the bloodstream. Having tubings inserted into blood vessels for long for infusions of medicines and fluids makes a portal of entry of bacteria into the bloodstream and then to the heart.
BE can cause signs and symptoms which may vary over time and may differ in individuals. A few endocarditis symptoms are mentioned below. The commonest ones are the flu-like symptoms such as;
There are several potential complications in BE. The bacterial colonies growing along the edges of the valves may fragment and then be carried away in the bloodstream. These fragments called emboli can block other smaller blood vessels in the lungs, spleen, kidneys, or brain. This can cause the death of tissues called infarction in these organs.
Bleeding into the brain, called brain hemorrhage, and the failure of the heart or kidneys may occur. If blood vessels in the bones are occluded by these emboli, it can cause bone pains. The emboli may be infected with bacteria and hence may spread the infection throughout the body causing sepsis.
BE is diagnosed by using a battery of tests. The most common initial test is blood culture. Samples of blood drawn at regular intervals are tested for causative organisms which are then allowed to grow under laboratory conditions. These may then be isolated and tested for their sensitivities to anti-infective medicines.
Other blood tests include a count of different cells in the blood, called a complete blood count (CBC), and tests for some markers of inflammation.
An analysis of the inner heart lining and valves is done with an echocardiogram that works on the reflection of sound waves. This may be done through the chest (transthoracic echo) or the food pipe (transesophageal echo). The latter is more precise as it allows a closer and more direct view of the heart.
An electrocardiogram (ECG) may be done to check the electrical activity, beating, and rhythmicity of the heart though it is not conclusively diagnostic of BE. This is done by placing sensors containing paddings at some specific points on the body. The diagnosis of BE is made in accordance with the Duke’s criteria which comprises major and minor criteria.
The presence of typical organisms, the positive spread of bacteria in the bloodstream (bacteremia), positive testing for bacteria called Coxiella brunetii, positive culture, and a positive result on echo is the major criteria.
The minor criteria include the presence of fever greater than 38° C, valvular heart disease, skin lesions, drug abuse using injections into blood vessels, the presence of single positive blood culture, and suggestive findings on echo. BE is diagnosed in presence of one major and three minor criteria.
BE is treated with medicines to fight infection called antibiotics which are given as injections into the blood vessels (Intravenous or IV route) for up to 6 weeks.
The common antibiotics used for treatment are penicillin, ceftriaxone, vancomycin, and a combination of penicillin, ceftriaxone, or vancomycin and gentamicin.
A damaged or heavily infected heart valve, whether natural or artificial, may need to be replaced surgically. Surgery may be done to clean up the heavy growing colonies.
BE can be prevented. It is important to seek medical help at the very first suggestive symptoms.