Clinical impact of transesophageal echocardiography in the diagnosis and management of infective endocarditis.

Transesophageal echocardiography (TEE) has assumed a prominent role in the diagnosis and management of infective endocarditis (IE). The impact of negative TEE findings on the management of patients suspected of having IE is not clear. To better understand how a negative TEE examination would influence patient management, the medical records of 93 consecutive patients undergoing TEE to evaluate for IE were examined. The influence of TEE was assessed based on changes in diagnosis, antibiotic therapy, or the need for surgical intervention during hospitalization. The negative predictive value of TEE was found to be 100% in native valves and 90% in prosthetic valves. The overall impact of negative TEE findings was significant in terms of final diagnosis and duration of antibiotic therapy (a negative TEE resulted in 60% reduction in antibiotic duration, p = 0.0001). These findings suggest that in patients with native heart valves, a negative TEE examination virtually excludes IE. In patients with prosthetic valves, a negative TEE significantly decreases the likelihood of IE but does not completely exclude the diagnosis; therefore, in this setting, a negative finding should be closely correlated with the clinical course.

Relation of mean pixel intensity to concentration of sonicated albumin microspheres: effects of ultrasound system settings.

Myocardial contrast echocardiography (MCE) is a recently developed technique to assess myocardial perfusion. Previous studies have shown that MCE frequently underestimates coronary reserve as compared with other methods. Previous reports have suggested that some of the limitations of MCE are due to the nonlinear processing algorithms of the ultrasound systems. Therefore we designed an in vitro model to study the effects of various processing algorithms and levels of acoustic power (AP) on the relation between concentration of echocontrast and mean pixel intensities. A beaker containing a commercially produced, diluted solution of sonicated albumin microspheres was imaged with a commercial Hewlett Packard ultrasound system, and mean pixel intensities were determined with an off-line computer system. The solution was imaged at a wide range of APs (40-10 dB) and time gain compensation (40-60 dB). Concentration versus intensity curves were generated using all possible combinations of compression and processing algorithms available on the ultrasound system used. Contrast effect diminished rapidly when exposed to high AP. Lower powers had less effect on contrast intensity duration, with no effect seen below 20 dB. Changes in time gain compensation did not affect contrast intensities. Regardless of the processing algorithm examined, the relation between concentration of echocontrast and mean pixel intensities was near linear in the first two to three concentrations; thereafter, the curves flattened during increasing concentrations of contrast. At higher concentrations, acoustic shadowing produced a decrease in pixel intensities.(ABSTRACT TRUNCATED AT 250 WORDS)