Bacterial endocarditis in idiopathic hypertrophic subaortic stenosis.

Bacterial endocarditis complicating idiopathic hypertrophic subaortic stenosis (IHSS) is uncommon but endocarditis may be the first clinical manifestation of IHSS. In this report of such a case, the aortic and the mitral valves were the sites of the bacterial infection. Many chordae tendineae to the mitral valve were ruptured from the extension of the infectious process. The endothelial lesions, which served as the seat for the bacterial infection on the anterior mitral leaflet, likely resulted from its abutting action against the septal prominence. Damage to the aortic valve leaflet may have resulted from abnormal valve motion caused by IHSS and created an environment conducive to endocarditis. This patient developed aortic insufficiency during the course of bacterial endocarditis, suggesting that the occasional association of aortic insufficiency in patients with IHSS may be secondary to healed endocarditis of the aortic valve.