Infective endocarditis (IE) is an infection of the endocardial surfaces of the heart, which includes 1 or more heart valves. The incidence of infective endocarditis hospitalization in the United States is estimated at 12.7 per 100,000, annually.[1] A majority of the patients (57.7%) were male and more than a third were at the age of 70 and older.[1] Several risk factors predispose patients to IE, such as structural heart disease (valvular disease or congenital heart disease), prosthetic heart valves, indwelling cardiovascular device, an intravascular catheter, chronic hemodialysis, human immunodeficiency virus infection, diabetes, or history of infective endocarditis. Other risk factors include male older than 60 years, male gender, intravenous (IV) drug use, poor dentition, or dental infection. Infective endocarditis may present as acute or subacute infection.[2] Acute infections present as a rapidly progressive disease with high fevers, rigors, and sepsis. On the other hand, subacute bacterial endocarditis diagnosis is often delayed and presents as non-specific symptoms such as weight loss, fatigue, dyspnea over several weeks to months. There are several differences between subacute bacterial endocarditis and acute bacterial endocarditis. Most cases of subacute bacterial endocarditis are caused by penicillin sensitive Streptococcus viridans, while Staphylococcus aureus causes most cases of acute bacterial endocarditis.[3] Subacute bacterial endocarditis mostly happens in pre-existing heart disease while acute bacterial endocarditis mostly happens in healthy hearts.[3] After treatment, subacute bacterial endocarditis rarely leads to severe cardiac damage; however, most patients who survive acute bacterial endocarditis often die of cardiac failure within weeks or months.[3]  

As the incidence of infective endocarditis continues to rise in the United States, healthcare providers must make appropriate decisions regarding antibiotic prophylaxis to prevent further complications. Antibiotic prophylaxis before procedures, especially dental procedures, used to be widely utilized to prevent infective endocarditis despite a lack of established evidence to support this practice. In guidelines published by the American Heart Association (AHA) in 2007, the recommended indications to use antibiotics for endocarditis prophylaxis were significantly restricted.[4] There were several reasons for this change. Firstly, infective endocarditis was more likely to occur with everyday activities such as teeth brushing and flossing rather than with a single medical or dental procedure. Secondly, it was felt that prophylaxis with antibiotics for dental procedures prevented very few IE cases.[4] The cost of antibiotic therapy and the risk of adverse events and risk of promoting antibiotic resistance significantly outweighed the benefit of such prophylaxis. Thirdly, consistently good oral hygiene is considered more beneficial in preventing IE than a single dose of antibiotics.[4]

The function of prophylactic therapy for subacute bacterial endocarditis are the following:

1. Infective endocarditis is a fatal disease, and prevention is preferable to treatment of established infection.
2. Specific cardiac conditions predispose to infective endocarditis.
3. Reduce the incidence of bacteremia associated with invasive dental, oral, gastrointestinal (GI), and genitourinary (GU) tract procedures.
4. In animal studies, it was proven that antimicrobial prophylaxis to be effective for the prevention of infective endocarditis.
5. In humans, it is thought that antimicrobial prophylaxis to be effective for the prevention of IE in dental, oral, GI, or GU tract procedures.

Infective endocarditis is fatal if untreated or unrecognized. It causes significant morbidity and mortality, despite present-day advances in antimicrobial therapy and surgical treatment. As a result, the prevention of infective endocarditis is necessary. Some animal studies have shown antibiotics prophylaxis to prevent infective endocarditis, but the data in humans is still lacking. Current guidelines in the United States still recommend the use of antimicrobial prophylaxis for patients undergoing several procedures who are at risk for infective endocarditis.

The American Heart Association currently recommends antibiotic prophylaxis only in patients with the following high-risk cardiac conditions:

1. Patients with prosthetic cardiac valves
2. Patients with previous infective endocarditis
3. Cardiac transplant recipients with valve regurgitation due to a structurally abnormal valve
4. Patients with congenital heart disease with:

• Unrepaired cyanotic congenital heart disease, including palliative shunts and conduits,
• Totally repaired congenital heart defect repaired with prosthetic material or device that has been placed by surgery or catheter intervention, during the first 6 months after the procedure
• Repaired congenital heart disease with residual defects at the site or adjacent to the site of a prosthetic patch or prosthetic device

Patients with these high-risk conditions should receive antibiotics for the following procedures:

1. Dental procedures that involve manipulation of gingival tissue, manipulation of the periapical region of teeth, or perforation of the oral mucosa. This does not include routine anesthetic injections through noninfected tissue, dental radiographs, placement or adjustment of orthodontic devices or trauma to the lips and teeth.[4][5][4]
2. The 2007 AHA guidelines also recommended prophylaxis for invasive respiratory tract procedures that involve incision or biopsy of the respiratory mucosa (e.g., tonsillectomy, adenoidectomy). Antibiotic prophylaxis has not been recommended for bronchoscopy unless the procedure involves incision of the respiratory tract mucosa.[4]
3. Procedures of infected skin, skin structures, or musculoskeletal tissue.[4]

Prophylaxis against IE is not recommended in patients who are at risk of IE for other nondental procedures, for example, TEE, esophagogastroduodenoscopy, colonoscopy, or cystoscopy, in the absence of active infection.[4][6][7][4]

Patient's ability to tolerate oral medication are influenced by medication allergies, and by the most likely pathogen. For dental and respiratory procedures, the most common bacteria are the various Streptococcus viridans species. The recommended prophylactic antibiotic is amoxicillin 2 grams orally 1 hour before the procedure. If the patient needs intravenous (IV) medication, ampicillin or ceftriaxone may be used. Cephalexin, clindamycin, or azithromycin may be used in patients with a penicillin allergy. There is new penicillin resistance of the Streptococcus viridian. The prescribing physician must consider the resistance in his/her area of practice when prescribing the appropriate antibiotic. In cases where Staphylococcus aureus is suspected, antistaphylococcal penicillin or vancomycin is recommended.

Currently, there is no indication for dental, gastrointestinal, or genitourinary procedural prophylaxis for patients with implantable cardiovascular devices. However, prophylaxis with an anti-staphylococcal antibiotic is indicated at the time of cardiovascular device implantation and any subsequent manipulation of the surgically created device pocket.

For patients who have undergone coronary artery bypass graft surgery, antibiotic prophylaxis is not needed for dental procedures, as there is no increased risk of long-term infection.  Similarly, for patients with coronary artery stents, antibiotic prophylaxis is not needed for dental procedures.[4]

Further studies to evaluate the efficacy of antimicrobial prophylaxis in the prevention of infective endocarditis are needed.[8][9][10]