Patrick J. Lynch

Comparison and reproducibility of visual echocardiographic and quantitative radionyclide left ventricular ejection fractions

Left ventricular (LV) ejection fraction (EF) is commonly assessed by equilibrium radionuclide angiography and echocardiography. These methods are presumed to be interchangeable for this purpose. This study (1) compares quantification of LVEF by equilibrium radionuclide angiography with visual estimation of LVEF by echocardiography, (2) determines the reproducibility of both methods, and (3) evaluates whether differences in determinations of LVEF are of clinical relevance. Seventy-three clinically stable patients had both equilibrium radionuclide angiography and echocardiography performed within a 4-day period. LVEF by both techniques was compared after blinded analysis by 3 echocardiographers and 3 nuclear technologists. Reproducibility was assessed by blinded repeat analysis after a 1-week interval. The frequency of differences in repeat assessments of EF that the authors considered to be of potential clinical relevance (i.e., difference > or = 10% EF units) was assessed for both techniques. Correlation of LVEF determined by both methods was good (r = 0.81, SEE = 3.5) but with substantial differences in individual patients (limits of agreement, 23.6%). Intra- and inter-observer reproducibility was good for both methods, but better for radionuclide LVEF than for echocardiographic LVEF. Limits of agreement were substantially better for radionuclide LVEF than for echocardiographic LVEF (1.8% to 3.6% versus 13.4% to 17.4%, respectively). Clinically relevant differences did not occur on repeat processing of equilibrium radionuclide angiography. In contrast, potentially clinically relevant differences occurred in 8% to 26% of studies on repeat analysis of echocardiography. Thus, LVEF determined by equilibrium radionuclide angiography and echocardiography show good agreement. Both methods provide clinically valuable measurements for LV function. However, when a precisely reproducible measurement is required for patient management decisions, equilibrium radionuclide angiography is the method of choice.

Aesthetics and trust: visual decisions about web pages

Eyetracking studies seem to suggest that users do not look at large expressive graphics on web pages [1,2], as seen in the relatively few gaze fixations such graphics attract from users in task-driven eyetracking studies. However, many studies show that users react in very fast important ways to the overall design of web pages, and that such reactions have a profound effect on users judgments of the usability, aesthetic merit, and trustworthiness of web page designs [3,4].

Hypermedia and echocardiography: an interface design for guided discovery

INTRODUCTION: ECHOCARDIOGRAPHY Echocardiogmphy is a noninvasive ultrasound technique that allows two-dimensional real-time imaging of cardiac function. By aligning an external “probe” at a limited number of sites, it is possible to generate different “views” of cardiac function which can be used for diagnosis. Despite the importance of this technique, diagnostic training is usually restricted to a small group of residents because of the demands of individualized training by a specialist in radiology or cardiology. In order to overcome this obstacle, we are evaluating a hypermedia system as a means to provide such individualized training. Our implementation includes: echocardiograms from actual patient cases stored on videodisc; schematic images focusing on the essential elements in those displays; anatomical characterizations of the heart; textual descriptions of structure, function, and disease; organizational charts providing a means to associate various types of information; and cardiac sound as normally heard through a stethoscope.