Use of antimicrobial prophylaxis for prevention of bacterial endocarditis is based on theoretical advantage rather than data from clinical trials.
The 2007 American Heart Association (AHA) guideline for the prevention of infective endocarditis (IE)  made major revisions to the 1997 AHA guideline, the 2005 update of those guidelines published by the Medical Letter , and the 2006 American College of Cardiology (ACC)/AHA guideline on the management of valvular heart disease . Since the publication of the 2007 AHA guideline, the ACC/AHA guideline was updated several times, most recently in 2014 . The 2009 European Society of Cardiology (ESC) guidelines are largely in agreement with the American guidelines .
The theoretical basis for use of antimicrobial prophylaxis for prevention of bacterial endocarditis and the American Heart Association 2007 guideline on the prevention of infective endocarditis will be reviewed here .
The pathogenesis of infective endocarditis (IE) is presumed to involve the following sequence of events :
●Formation of a small thrombus on an abnormal endothelial surface