NORD gratefully acknowledges Katherine McGuckin & Brett Segobiano, NORD Editorial Interns from the University of Notre Dame, Barb Calhoun, MSN, RN, NP, Nurse Practitioner and Outreach Coordinator, Boler-Parseghian Center for Rare and Neglected Diseases at the University of Notre Dame, and Catherine M. Otto, MD, Editor-in-Chief, Heart; J. Ward Kennedy-Hamilton Endowed Chair in Cardiology; Professor of Medicine, University of Washington, for assistance in the preparation of this report.
Infective endocarditis (IE) is an infection of the inner lining of the heart muscle (endocardium) caused by bacteria, fungi, or germs that enter through the bloodstream. IE occurs most frequently in patients with abnormal (leaky or narrow) heart valves, artificial (prosthetic) heart valve or in people who have a pacemaker lead. Any structural heart disease can predispose a person to developing IE. In the past, rheumatic fever was the main precursor to IE and still remains a common predisposition in developing countries. The presenting symptoms are a low-grade persistent fever without an obvious cause, fatigue and shortness of breath on exertion. Patients also may have joint and muscle pain and their health care provider may hear a new or changing murmur.
The endocardium covers the heart valves, and it is these valves which are primarily affected by infective endocarditis. If the infection remains untreated, multiplying bacteria may eventually destroy the valves and result in heart failure. Bacteria may also form small clots (emboli) which move through the blood and block small arteries. These clots may lodge in various parts of the body including the brain and cause serious damage.
The prevalence of cases of IE has risen in the United States due to the increase in the number of elderly patients receiving invasive surgeries as well as the rise in the number of individuals using IV drugs. Other risk factors include congenital heart disease, prior episode of IE and mitral valve prolapse with leaky valve. Therefore, early diagnosis is key to improve clinical outcomes and survival. Antibiotics are essential for treatment and are most effective if the disease is caught early. However, in many cases heart surgery also is needed.
Endocarditis was first described by William Osler in 1885. Developments in medical science and research in microbiology have contributed to a better understanding of the disease. The most common risk factors for infective endocarditis are previous heart damage, recent heart surgery or poor dental hygiene.
Infective endocarditis is an infection of the valves and/or lining of the heart. The presenting symptoms are a low-grade persistent fever without an obvious cause and fatigue and shortness of breath on exertion. Patients also may have joint pain (arthralgia) and muscle pain (myalgia) and their health care provider may hear a new or changing murmur. In addition, the following signs and symptoms occur:
Infection on the heart valve results in destruction of the leaflet tissue, leaking of the valve and heart failure. Extension of infection into tissue next to valve may result in an abscess with rupture between different chambers of the heart. Clots (emboli) resulting from infective endocarditis may produce serious damage. Symptoms depend upon the location of the clot. In 20-40% of individuals with infective endocarditis, clots lodge in the brain and may cause weakness on one side of the body, loss of vision or stroke. Clots may also cause abdominal pain, flank pain, or arterial insufficiency in an extremity. An eye doctor might see bleeding in the back of the eye (Roth spots). Damage from clots may be temporary or permanent.
Bacteria that cause infective endocarditis reach the heart through the bloodstream. Normally, heart valves are highly resistant to the attachment of bacteria and resulting infection. Damage to the heart valves and inner lining of the heart is the main risk factor for infective endocarditis because it leaves the tissue susceptible to bacterial overgrowth. As the microorganisms quickly move past the damaged valve lining, those strains that can most strongly adhere to the surface are bacteria that have the best chance of producing infective endocarditis. Clumps of bacteria and cells called vegetations form on the heart valves affecting proper function of the heart. If left untreated, this vegetation may cause the valve to leak or may result in an abscess next to the valve or in the heart muscles leading to tissue damage and blockage of the normal electrical conduction pathways. In addition, the vegetation may break loose and cause damage to the brain (stroke), kidneys or lungs.
Risk factors that contribute to the onset of Infective Endocarditis include:
People who are on immunosuppressive medication (such as after heart transplantation) also are at higher risk. In patients with risk factors, any dental procedure (including routine dental cleaning) risks the spread of bacteria which is prevented by treatment with antibiotics just before dental procedures in people at highest risk. Infections elsewhere in the body and chronic indwelling catheters (such as for chemotherapy) also increase the risk of infective endocarditis.
Approximately 80% of infective endocarditis cases are caused by the bacteria streptococci and staphylococci. The third most common bacteria causing this disease is enterococci, and, like staphylococci, is commonly associated with healthcare-associated infective endocarditis. While very rare, infections due to gram-negative and fungal pathogens are often acquired in healthcare settings.
The mouth is a major portal for bacteria to enter the body, specifically streptococcal bacteremia. Historically, prophylactic treatment with antibiotics was used for all patients at high risk for developing IE when undergoing surgical, dental or other invasive procedures. The American Heart Association recommended penicillin prophylaxis in 1955 for patients with congenital heart disease and rheumatic heart disease prior to undergoing any dental procedures. Emerging resistance to antibiotics due to overuse and lack of research to support the use of prophylaxis led the USA and Europe to restrict the use of antibiotics by 2009. The United Kingdom went on to abandon the use of antibiotic prophylaxis entirely. The USA reserves this treatment for those with prosthetic heart valves, prior IE, congenital heart disease and cardiac transplant recipients.
Infective endocarditis appears to be approximately twice as common in men as women. In the past, disease onset occurred at an average age of 35 years of age. However, with more patients having artificial heart valves and pacemakers, the average age at onset has increased to over 50 years. Infective endocarditis has an incidence rate of 3-10 cases in every 100,000 people. No race or ethnicity is more affected than others. Prognosis of infective endocarditis remains poor despite advances in diagnosis and therapies. Mortality rates are approximately 25% even with the best therapies available.
Infective endocarditis most commonly affects people who:
For those with heart valve replacements, the risk of infection is highest within the first year after the procedure takes place. Those who have had this type of procedure remain at higher risk for infective endocarditis for the rest of their life compared to those who have not had these procedures.
Acute bacterial endocarditis is usually caused by staphylococcus aureus bacteria and occasionally by the bacterial strains brucella and listeria. This form of infective endocarditis, compared to other forms, is more likely to affect normal heart valves.
Subacute bacterial endocarditis is usually caused by streptococcal bacteria. This form of the disease usually develops on damaged valves after dental surgery involving infected gums, reproductive or urinary (genitourinary tract) surgery or operations on the gastrointestinal tract. A history of a preceding dental, genital or urologic procedure is common. Symptoms usually begin within two weeks following the procedure, but diagnosis is often delayed because symptoms are subtle and patients may not seek care immediately and because diagnosis can be difficult, especially early in the disease course. A previous history of heart disease is present in most individuals with subacute bacterial endocarditis.
In developing countries, heart damage caused by rheumatic heart disease is the leading predisposing condition for infective endocarditis; however in developed countries, rheumatic heart disease is implicated in less than 5% of infective endocarditis cases.
Prosthetic valvular endocarditis (PVE) develops in 2% to 3% of individuals in the year following artificial (prosthetic) valve placement or tissue valve replacement, occasionally resulting from organisms accidentally implanted during surgery. The number of reported cases of prosthetic valvular endocarditis is highest with artificial aortic valve replacement. These infections frequently result from contamination during an operation. Approximately 30% of the reported cases are caused by staphylococcus.
The key step in the diagnosis of endocarditis is obtaining blood cultures before antibiotics are started. People with risk factors for endocarditis, particularly those with prosthetic valves and pacemakers, should know the symptoms of endocarditis and should insist on blood culture when they have an unexplained fever. Diagnosis of infective endocarditis can be done based on pathology or by meeting certain clinical diagnostic criteria. These criteria are known as the Duke Clinical Criteria and a patient must show either: 2 major, 1 major and 3 minor, or 5 minor criteria to be diagnosed with infective endocarditis. These include
Major Clinical Criteria
Minor Clinical Criteria
Cardiac CT scan (computed tomography), an imaging test, may be indicated in the event the results of TTE and TEE are inconclusive and clinical presentation is consistent with IE.
Without prompt, appropriate treatment, infective endocarditis results in serious heart damage or death. Mortality rate within the first 30 days of infection has been reported to be ~20% but survival without antibiotic therapy is unlikely. Therefore, early diagnosis and aggressive therapy are critical for successful treatment. Therapeutic measures typically include intravenous infusion of high doses of appropriate antibiotic drugs. Antibiotic therapy is needed for at least six or eight weeks and is provided intravenously for at least 2 weeks and often for the entire treatment duration. The specific drugs or drug combinations used may depend upon the bacterium responsible for the infection and other factors (e.g., bacterial strain resistance to certain antibiotics). The specific antibiotics uses in each patient are selected based on the blood culture results and determining which antibiotics kill the specific bacteria isolated in each patient. Often more than one antibiotic is given together to increase effectiveness. The type of antibiotic needed will be determined in consultation with infectious disease specialists.
In many affected individuals, antibiotics alone are not sufficient to control the infection, because the antibiotics cannot reach the infected valve material or abscess. In patients with a prosthetic heart valve or other implanted material, surgery is almost always needed to remove the infected artificial material and repair the heart. Surgery also is needed if there is an abscess with blockage of the heart electrical signal, rupture between chambers of the heart, or persistent infection even with antibiotic therapy. In patients with an infected pacemaker or lead, the entire pacemaker system usually needs to be removed to control the infection. Surgery may also be recommended if there is heart failure due to severe valve leakage or if vegetation is large to prevent stroke. In many cases, heart surgery may be recommended urgently, during the same hospitalization. In other patients, surgery may be done at a later date, after completing antibiotic treatment.
In 2015, The European Society of Cardiology developed guidelines for the treatment of infective endocarditis. These guidelines provide clear, simple recommendations for health care providers in diagnosis and treatment of IE: https://academic.oup.com/eurheartj/article/36/44/3075/2293384#108779576
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