The AHA recom- mends that for those in the highest-risk groups, prophylactic antibiotic drugs before certain dental procedures may be considered3 (Class IIb; Level of Evidence C). Table 11. Echocardiographic Features Suggesting Potential Need for Surgical Intervention* Vegetation Persistent vegetation after systemic embolization Anterior mitral leaflet vegetation, particularly with size >10 mm 1 Embolic event during first 2 wk of antimicrobial therapy 2 Embolic events during or after antimicrobial therapy Increase in vegetation size after 4 wk of antimicrobial therapy Valvular dysfunction Acute aortic or mitral insufficiency with signs of ventricular failure Heart failure unresponsive to medical therapy Valve perforation or rupture Perivalvular extension Valvular dehiscence, rupture, or fistula New heart block Large abscess or extension of abscess despite appropriate antimicrobial therapy *See text for more complete discussion or indications for surgery based on vegetation characterizations. Surgery may be required because of risk of recurrent embolization. Surgery may be required because of risk of embolization. Surgery may be required because of heart failure or failure of medical therapy. Reprinted from Bayer et al.102 Copyright 1998, American Heart Association, Inc. 