100 QUESTIONS IN CARDIOLOGY

99 Which patients should receive antibiotic

prophylaxis for endocarditis, and which procedures

should be covered in this way?

Peter Wilson

There is little firm scientific evidence for present advice on

antibiotic prophylaxis for endocarditis, mainly because of the rarity

of the disease. Only 10% of cases are related to bacteraemia caused

by invasive procedures. Prevention of endocarditis in patients with

abnormal heart valves can be achieved by many general measures,

for example, regular dental care. The convention for the use of

antibiotics in the prevention of endocarditis derives from animal

models and clinical experience. Although dental extraction results

in a bacteraemia of about 100cfu/mL, no obvious relationship has

been found between the number of circulating bacteria and the

likelihood of developing endocarditis.

In man, case-control studies suggest 17% of cases might be

prevented if prophylaxis is given for all procedures in patients

with abnormal valves.^1 Individual cases of endocarditis

following dental or urological procedures have been reported but

the risk of developing endocarditis must be very low. Underlying

cardiac abnormalities greatly increase the risk of endocarditis,

e.g. patent ductus arteriosus, prosthetic valves, hypertrophic

cardiomyopathy, aortic valve disease or previous endocarditis.

Mitral valve prolapse is common but merits antibiotic prophy-

laxis if it causes a murmur.

Procedures causing gingival bleeding should be covered by

prophylaxis as should tonsillectomy, adenoidectomy and dental

work. Other procedures in which prophylaxis should be used

include oesophageal dilatation or surgery or endoscopic laser

procedures, sclerosis of oesophageal varices, abdominal surgery,

instrumentation of ureter or kidney, surgery of prostate or urinary

tract. Flexible bronchoscopy with biopsy, cardiac catheterisation,

endoscopy with biopsy, liver biopsy, endotracheal intubation and

urethral catheterisation in the absence of infection do not need

prophylaxis. Patients having colonoscopy or sigmoidoscopy

probably do not require prophylaxis unless there is a prosthetic

valve or previous endocarditis or unless biopsy is likely to be

performed. Recommendations for prophylaxis in patients under-

going obstetric or gynaecological procedures are required for