Overview: Antibiotics are antimicrobial medications, used against infections.

HCM patients who develop infective endocarditis (a bacterial infection of the heart lining) are at greater risk of serious complications than other patients. 

Infective endocarditis is not common, but it can cause severe valve damage. It is often fatal if left untreated. Oral bacteria are an important source of  infective endocarditis. Gum bleeding caused by dental work can permit these bacteria to enter the bloodstream and cause endocarditis.

Antibiotic treatment before dental work can greatly reduce this risk. For this reason, general practice for many years was for patients at relatively high risk (such as those with certain valve problems or artificial valves, transplant patients, and those with HCM) to take a single dose of an antibiotic an hour before dental work. Giving an antibiotic (typically, amoxicillin) ahead of dental work was incorporated in guidelines from the American Heart Association (AHA) and a number of specialist societies in 1997.

In recent years, there has been some debate about this practice. A 2007 revision of the AHA guidelines suggested that prophylactic antibiotics before dental work should be prescribed only for those with the greatest risk of serious damage from infective endocarditis. The argument for the change is that there are no randomized, controlled trials supporting prophylactic antibiotics, and there is a risk of anaphylaxis (dangerous allergic response) to antibiotics. Leading HCM specialists criticized this change in the guidelines. They argue that randomized trials would be difficult at best to conduct for a condition that is relatively uncommon. Also, since there are no published cases of anaphylaxis in patients taking a single prophylactic dose of these drugs, the risk appears very small. Many HCM specialists continue to prescribe antibiotics before dental work. At least one prospective study supports this practice.

Antibiotics can be problematic to HCM patients in one other context: a group of antibiotics called fluoroquinolones can cause serious damage to heart valves. This group of drugs includes ciprofloxacin (Cipro), gemifloxacin (Factive), levofloxacin (Levaquin), moxifloxacin (Avelox), and ofloxacin (Floxin). Fluoroquinolones are more than twice as likely to cause valve damage as other antibiotics. The heart problems caused by fluoroquinolones are not common, and under some circumstances they may still be the best choice. But you should consult with your cardiologist about taking them.

HCMA 6/2021