Antibiotic prophylaxis to prevent infective endocarditis

Archie Ying-sui Lo 羅鷹瑞

HK Pract 2015;37:143-145

Summary

Use of pre-operative antibiotic prophylaxis (PAP) against infective endocarditis (IE) has often been overly enthusiastic. Most guidelines since 2008 have endorsed a major paradigm shift that emphasises restraint in prescribing PAP.

PAP should be prescribed only for patients who carry the highest risk medical diagnoses, and who are undergoing the highest risk procedures. Native valvular regurgitation/stenosis generally do not require AP any more.

The highest risk conditions include prosthetic heart valves, complex congenital heart disease, prior infective endocarditis and valvulopathy in a transplanted heart, while the highest risk procedures mainly comprise selected dental and respiratory tract procedures.

摘要

過往一向都非常重視在手術前使用抗生素預防感染性心內膜炎。然而，從2008年開始，多數臨床指引都作出指導性改變： 強調需 要節制地 使用術前抗生素。認為預防性抗生素只 適用於最高風險的心臟病患者，和在接受最高風險的外科程式時使用。心瓣膜反流或狹窄，一般不再需要預防性抗生素。屬於最高風險的疾病包括人工瓣膜、複雜發紺性先天性心臟病、曾患感染性心內膜炎和在移植心臟內的心臟瓣膜病；而屬於最高風險的程式主要包括入侵性的牙科（包括洗 牙)和呼吸道手術。除非正值患上感染， 否則腸胃科、泌尿科和產科手術通常無需作術前抗生素預防。

lntroduction

In both inpatient and outpatient practices, cardiologists have often received calls from dentists, endoscopists or surgeons enquiring about whether their patients with cardiac conditions, especially those with valvular lesions, require pre-operative antibiotic prophylaxis (PAP).

Most cardiologists can still remember the days when PAP was advised for common valvular lesions such as mitral valve prolapse with trivial mitral regurgitation or mild aortic regurgitation. However, the 2007 American Heart Association (AHA) guideline for the prevention of infective endocarditis (IE) was published with a major paradigm shift, supporting the use of PAP only for patients with the highest risk medical conditions undergoing high risk procedures.¹

Since 2007, the joint American College of Cardiology/AHA guidelines on the management of valvular heart disease had been updated several times, most recently in 2014.² The 2009 European Society of Cardiology (ESC) guidelines³ are largely in agreement with the American guidelines. The United Kingdom’s National Institute for Health and Clinical Excellence (NICE) recommended complete cessation of antibiotic prophylaxis for prevention of IE in March 2008.⁴ After years of monitoring, NICE announced on 1st June 2015 that its original guidance on the use of antibiotics to prevent infective endocarditis will remain unchanged following a review of evidence published since the 2008 guidance.⁵

The tendency to prescribe PAP may have markedly decreased in America and Europe since 2009. However, it appears that many physicians in Hong Kong still continue to prescribe PAP despite the new guidelines. Clearly the overly aggressive PAP regimens in the past are now deemed inappropriate, because it results in widespread antibiotic resistance, increases medical costs, and causes antibiotic-related side effects. Patients often complain about having to ingest 10 pills all at once (ampicillin). Often, medications for “preventing” gastric discomfort will also be prescribed, thus contributing to polypharmacy.

Rationale for the need to exercise restraint in prescribing PAP

There has been no human study to-date demonstrating that PAP can prevent endocarditis after invasive procedures. Observational studies have provided, at best, conflicting evidence of treatment benefit.^6-9 The 2007 AHA guideline concluded that “bacteraemia resulting from daily activities is much more likely to cause IE than bacteraemia associated with a dental procedure; that only an extremely small number of cases of IE might be prevented by PAP even if prophylaxis is 100% effective; that PAP is not recommended based solely on an increased lifetime risk of acquisition of IE”.

PAP can fail as well and IE may still occur despite its administration prior to surgical procedures, even though the majority of the pathogens were susceptible to the PAP agents administered.¹⁰ Epidemiologic studies have reported that up to 5% of all cases of IE are preceded by a dental procedure.¹¹ However, despite a close temporal relationship between a dental procedure and the occurrence of IE, it is always difficult to ascertain as to whether IE occurred as a complication of the dental pathology that led to the procedure to begin with, or from routine tooth brushing.

Indications for PAP

According to the 2007 AHA guideline¹, PAP should only be prescribed for patients who carry the highest risk medical diagnoses, and who are undergoing the highest risk procedures (those likely to result in bacteraemia with a microbe that has the potential to cause IE).

The AHA guideline considers the following as the highest risk medical conditions:

• Prosthetic heart valves, including bioprosthesis and homografts.
• History of prior IE.
• Selected congenital heart disease:
  • Unrepaired cyanotic congenital heart disease, including palliative shunts and conduits.
  • Completely repaired congenital heart defects with prosthetic material/device, whether placed by surgery or by catheter intervention, during the first 6 months post-procedure.
  • Repaired congenital heart disease with residual defects at the site or adjacent to the site of the prosthetic device. ( Except for the conditions listed above, PAP is no longer recommended for any other form of congenital heart disease, including VSD and ASD).
  • Cardiac valvulopathy in a transplanted heart.

It should be emphasised that common valvular lesions for which PAP was often prescribed in the past are no longer routine indications for PAP. These include acquired aortic stenosis/regurgitation, mitral stenosis/regurgitation, mitral valve prolapse with or without regurgitation, and bicuspid aortic valve. Obstructive hypertrophic cardiomyopathy is also not an indication any more.

The following are considered to be the highest risk procedures:

• Dental procedures. PAP is reasonable for those that involve manipulation of either gingival tissue or the periapical region of teeth, or perforation of the oral mucosa; routine dental cleaning is included. The following procedures and conditions do not need PAP: routine anesthetic injections through non-infected tissue, taking dental x-rays, placement of removable prosthodontic or orthodontic appliances, adjustment of orthodontic appliances, placement of orthodontic brackets, shedding of deciduous teeth, and bleeding from trauma to the lips or oral mucosa. The preferred regimen is amoxicillin 2g given 30 to 60 minutes before the procedure (oral); or cefazolin or ceftriaxone 1g (IM or IV); or if allergic to penicillins, cephalexin 2g, or clindamycin 600mg, or azithromycin/clarithromycin 500mg (oral). Penicillin-allergic patients unable to take oral drugs may be given cephazolin or ceftriaxone 1g (IM or IV), or clindamycin 600mg (IM or IV). For patients already on antibiotic(s) at the time of dental or other procedures, an antibiotic from a different class should be chosen. For example, if a patient on amoxicillin undergoes a dental procedure and requiring PAP, clindamycin, cefuroxime or clarithromycin can be chosen.
• Respiratory tract procedures. PAP is reasonable for those involving incision or biopsy of the respiratory tract mucosa, including tonsillectomy, adenoidectomy, or bronchoscopy with biopsy. Simple bronchoscopy without biopsy does not warrant PAP. Patients who undergo invasive respiratory tract procedures as part of treatment for an ongoing infection (such as drainage of empyema or abscess) should receive antibiotic coverage active against viridans group streptococci. For those with infections known or suspected to be caused by Staphylococcus aureus, coverage should be with agent(s) active against it.
• Genitourinary (GU) and gastrointestinal (GI) procedures. Routine PAP, in the absence of active infection, is not warranted for any GI or GU procedure, even for patients with high-risk cardiac conditions. Patients with high-risk cardiac conditions and ongoing GI or GU infection warrant therapy with activity against enterococci (amoxicillin or ampicillin); vancomycin is an alternative for those intolerant of beta-lactams.
• Skin and musculoskeletal infections - Patients with such infections undergoing procedures should receive agents active against staphylococci and beta-hemolytic streptococci.
• Obstetrical procedures - Routine PAP is not indicated for routine vaginal or cesarean delivery in the absence of active infection. It is reasonable to consider PAP against IE before vaginal delivery at the time of membrane rupture in select patients with high risk medical conditions, similar to what was listed above.

Conclusion

In summary, PAP has often been prescribed indiscriminately and should be reserved only for patients with the highest risk medical conditions undergoing high risk procedures which are likely to result in bacteraemia with a microbe that is potentially pathogenic for IE.