Endocarditis is defined at "exudative and proliferative inflammatory alterations of the endocardium, characterized by the presence of vegetations on the surface of the endocardium or in the endocardium itself, and most commonly involving a heart valve, but sometimes affecting the inner lining of the cardiac chambers or the endocardium elsewhere. It may occur as a primary disorder or as a complication of or in association with another disease".
Role of patient characteristics
As the Duke Criteria relies heavily on the results of echocardiography, research has addressed when to order an echocardiogram by using signs and symptoms to predict occult endocarditis among patients with intravenous drug abuse and among non drug-abusing patients . Unfortunately, this research is over 20 years old and it is possible that changes in the epidemiology of endocarditis and bacteria such as staphylococcus make the following estimates incorrectly low.
Among patients who do not use illicit drugs and have a fever in the emergency room, there is a less than 5% chance of occult endocarditis. Mellors  in 1987 found no cases of endocarditis nor of staphylococcal bacteremia among 135 febrile patients in the emergency room. The upper confidence interval for 0% of 135 is 5%, so for statistical reasons alone, there is up to a 5% chance of endocarditis among these patients. In contrast, Leibovici  found that among 113 non-selected adults admitted to the hospital because of fever there were two cases (1.8% with 95%CI: 0% to 7%) of endocarditis.
Among patients who do use illicit drugs and have a fever in the emergency room, there is about a 10% to 15% prevalence of endocarditis. This estimate is not substantially changed by whether the doctor believes the patient has a trivial explanation for their fever. Weisse found that 13% of 121 patients had endocarditis. Marantz  also found a prevalence of endocarditis of 13% among such patients in the emergency room with fever. Samet  found a 6% incidence among 283 such patients, but after excluding patients with initially apparent major illness to explain the fever (including 11 cases of manifest endocarditis), there was a 7% prevalence of endocarditis.
Clinical prediction rule. A clinical prediction rule, that has not been validated, suggests there is no chance of endocarditis in the absence of "vasculitic/embolic phenomena; the presence of central venous access; a recent history of injected drug use; presence of a prosthetic valve; and positive blood cultures".
Among patients with staphylococcus aureus bacteremia (SAB), one study found a 29% prevalence of endocarditis in community-acquired SAB versus 5% in nosocomial SAB. However, only 2% of strains were resistant to methicillin and so these numbers may be low in areas of higher resistance. The likelihood of endocarditis may be higher for MSSA than MRSA.
The role of electrocardiography has been addressed in clinical practice guidelines from theAmerican Heart Association, with endorsement by the Infectious Diseases Society of America, have been updated in 2015.
The transthoracic echocardiogram has a sensitivity and specificity of approximately 65% and 95% if the echocardiographer believes there is 'probabable' or 'almost certain' evidence of endocarditis.
Patients at highest risk of endocarditis should have early transesophageal echocardiography.
Computed tomographic cardiac angiography
About half of patients will require cardiac surgery.
Clinical practice guidelines for the United Kingdom have been created by the National Institute for Health and Clinical Excellence.
United States Guidelines
The following two lists are quoted from the guidelines:
- The committee concluded that only an extremely small number of cases of infective endocarditis may be prevented by antibiotic prophylaxis for dental procedures even if such prophylactic therapy were 100 percent effective.
- Infective endocarditis prophylaxis for dental procedures is reasonable only for patients with underlying cardiac conditions associated with the highest risk of adverse outcome from infective endocarditis.
- For patients with these underlying cardiac conditions, prophylaxis is reasonable for all dental procedures that involve manipulation of either gingival tissue or the periapical region of teeth or perforation of oral mucosa.
- Prophylaxis is not recommended solely on the basis of an increased lifetime risk of acquisition of infective endocarditis.
Highest risk cardiac conditions are:
- Patients with prosthetic heart valves and patients with a history of infective endocarditis. (Level of Evidence: C)
- Patients who have complex cyanotic congenital heart disease (e.g., single-ventricle states, transposition of the great arteries, tetralogy of Fallot). (Level of Evidence: C)
- Patients with surgically constructed systemic pulmonary shunts or conduits. (Level of Evidence: C)
- Patients with congenital cardiac valve malformations, particularly those with bicuspid aortic valves, and patients with acquired valvular dysfunction (e.g., rheumatic heart disease). (Level of Evidence: C)
- Patients who have undergone valve repair. (Level of Evidence: C)
- Patients who have hypertrophic cardiomyopathy when there is latent or resting obstruction. (Level of Evidence: C)
- Patients with MVP and auscultatory evidence of valvular regurgitation and/or thickened leaflets on echocardiography.low asterisk (Level of Evidence: C)
According to the 2006 clinical practice guidelines from the American Heart Association, the following patients are "Highest Risk of Adverse Outcome From Endocarditis for Which Prophylaxis With Dental Procedures Is Reasonable" if they are undergoing "dental procedures that involve manipulation of gingival tissue or the periapical region of teeth or perforation of the oral mucosa":
- "Prosthetic cardiac valve or prosthetic material used for cardiac valve repair"
- "Previous IE [infective endocarditis]"
- "Congenital heart disease (CHD)*"
- "Unrepaired cyanotic CHD, including palliative shunts and conduits"
- "Completely repaired congenital heart defect with prosthetic material or device, whether placed by surgery or by catheter intervention, during the first 6 months after the procedure"
- "Repaired CHD with residual defects at the site or adjacent to the site of a prosthetic patch or prosthetic device (which inhibit endothelialization)"
- Cardiac transplantation recipients who develop cardiac valvulopathy
- Anonymous (2023), Bacterial endocarditis (English). Medical Subject Headings. U.S. National Library of Medicine.
- Durack D, Lukes A, Bright D (1994). "New criteria for diagnosis of infective endocarditis: utilization of specific echocardiographic findings. Duke Endocarditis Service.". Am J Med 96 (3): 200-9. PMID 8154507.
- Weisse A, Heller D, Schimenti R, Montgomery R, Kapila R (1993). "The febrile parenteral drug user: a prospective study in 121 patients.". Am J Med 94 (3): 274-80. PMID 8452151.
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- Samet J, Shevitz A, Fowle J, Singer D (1990). "Hospitalization decision in febrile intravenous drug users.". Am J Med 89 (1): 53-7. PMID 2368794.
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- Marantz P, Linzer M, Feiner C, Feinstein S, Kozin A, Friedland G (1987). "Inability to predict diagnosis in febrile intravenous drug abusers.". Ann Intern Med 106 (6): 823-8. PMID 3579068.
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- Leibovici L, Cohen O, Wysenbeek A (1990). "Occult bacterial infection in adults with unexplained fever. Validation of a diagnostic index.". Arch Intern Med 150 (6): 1270-2. PMID 2353860.
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- Mellors J, Horwitz R, Harvey M, Horwitz S (1987). "A simple index to identify occult bacterial infection in adults with acute unexplained fever.". Arch Intern Med 147 (4): 666-71. PMID 3827454.
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