Similarly, perivalvular fistulas and pseudoaneurysms develop over time, and negative early TEE images do not exclude the potential for their development. False-positive results from TEE or TTE studies may occur when valvular abnormalities are seen that may not be related to a current infection. Previous scarring, severe myxomatous change, and even normal structures such as Lambl excres- cences may be indistinguishable from active changes in the valves. As echocardiographic technology improves with higher frequencies and refined beam-forming technology, subtle findings continue to be recognized and may add to the category of indeterminate findings. One approach to minimiz- ing confusion from these latter structures is to exploit the high frame rates that are often available with current equipment to improve temporal resolution and to clearly visualize rap- idly moving structures such as microcavities from prosthetic valves or fibrillar components. Several echocardiographic features identify patients at high risk for a complicated course or with a need for surgery (Table 5). These features include large (>10 mm in diameter) vegetations, severe valvular insufficiency, abscess cavities or pseudoaneurysms, valvular perforation or dehiscence, and evidence of decompensated heart failure.21 The ability of echo- cardiographic features to predict embolic events is limited.55 57 The greatest risk of embolic complications appears to occur with large ( 10 mm) vegetations on the anterior mitral leaf- Vegetation size and mobility may be taken into account, along with bacteriological factors and other indications for surgery, when considering early surgery to avoid emboliza- tion, although mobility characteristics alone should not be the principal driver as a surgical indication.59 Recommendation 1. TTE should be performed in all cases of suspected IE (Class I; Level of Evidence B). 