The clinical presentation of fever, new heart murmur, Janeway lesions, and positive blood cultures for Staphylococcus aureus in an IV drug user strongly suggests infective endocarditis. The definitive echocardiographic finding that would confirm this diagnosis is vegetation on heart valves. Vegetations are masses of platelets, fibrin, microorganisms, and inflammatory cells that attach to the heart valves. They are the hallmark finding in infective endocarditis and can be visualized on echocardiography, particularly transesophageal echocardiography which has higher sensitivity than transthoracic studies.
