Value of digital image processing of two-dimensional echocardiograms in differentiating active from chronic vegetations of infective endocarditis.

Abstract

The ability of a computer-based image digitizing system to differentiate "active" from "chronic" valvular vegetations was evaluated. Twenty-two patients with newly diagnosed infective endocarditis were studied prospectively by serial two-dimensional echocardiograms. Two comparable images (active and chronic) from the same patient taken several weeks apart (range, 4-17 weeks) after initiation of therapy were obtained at end diastole with identical gain settings. The images were digitized, magnified, and displayed on a high-resolution color monitor. The mean pixel intensity of the valvular vegetation in the active stage was 20.6 +/- 3.6 (mean +/- SD), which increased to 34.4 +/- 4.3 in the chronic stage (p less than 0.01). Because there was some overlap of values, an additional standardization procedure was used in the last eight patients. In these eight patients, the mean pixel intensity of the vegetations in the active stage was 17.5 +/- 1.1, and it increased at 4 weeks to 25.0 +/- 1.2 (p less than 0.05) and further increased in the chronic stage to 33.6 +/- 3.1 (p less than 0.05). There was no overlap of values between the active and chronic stages. Three clinical states are of particular interest: 1) The mean pixel intensity of the vegetations remained unchanged (23 vs. 24) in one patient who did not respond to antibiotic therapy. 2) The mean pixel intensity of the vegetations fell from 35 to 24 when one patient developed reinfection of the same valve, and with treatment, mean pixel intensity once again increased to 34. 3) The mean pixel intensity of the vegetations in five patients with culture negative infective endocarditis was low (21.6 +/- 1.9) and increased (33.6 +/- 6.0, p less than 0.05) during the chronic stage. The mean vegetation size was 0.73 +/- 0.30 cm2 in the active stage and decreased to 0.56 +/- 0.24 cm2 (p less than 0.05) in the chronic stage; however, in six of 22 patients (27%), vegetation size did not decrease with clinical cure.(ABSTRACT TRUNCATED AT 250 WORDS)