TEE examination is critical among patients with S aureus bacteremia, because the rate of endocarditis is significant.67 Several prognostic features may be better defined on transthoracic echocardiography than on TEE, such as pericardial effusion, ventricular dysfunction and dyssynchrony, and pulmonary vascular pressure estimations. Concomitant or subsequent transthoracic echocardiography acquired at the time of diagnosis of CIED infection can serve as a baseline for additional studies that may be required during the course of the patient s illness or follow-up. A mass adherent to the lead that is seen on echocardiog- raphy is usually a thrombus or infected vegetation. Because it is impossible to distinguish between the 2 with echocardiog- raphy and recognizing that 5% of adherent masses were deemed thrombus in 1 retrospective survey,68 there will be some patients who are labeled as manifesting CIED-related endocarditis who may not have a lead infection. Masses that are detected in patients without positive blood cultures or other suggestive features for infection are likely to represent thrombus and by themselves do not require lead removal or antibiotic treatment. In addition, the failure to visualize a mass adherent to a lead with TEE does not exclude lead infection. Cultures of generator-pocket site tissue and lead tips at the time of device removal are useful in identifying the causative organism and to support a diagnosis of CIED infection. The sensitivity of pocket-site tissue culture is higher than that of swab culture of the pocket.69 Gram staining, in addition to both anaerobic and aerobic bacterial cultures, should be done. Both tissue and the lead tip should be cultured for fungi and mycobacteria if the initial Gram stain is negative; mycobac- teria and fungal stains also should be obtained on resected pocket tissue. 