Limitations of digital subtraction contrast echocardiography in enhancing left ventricular endocardial definition

The purpose of this study was to evaluate whether the digital subtraction technique, applied to contrast echocardiography of the left ventricle (LV), might improve endocardial edge identification by two-dimensional echocardiography. Injections of the polysaccharide agent SHU-454 were made into the LV of five closed-chest dogs. Data were obtained at different levels of ejection fraction (EF) induced by pharmacologic or mechanical interventions and were documented by left ventriculography (VGRAM) in the right anterior oblique projection. Contrast echocardiography was recorded in the apical four-chamber view. The echocardiographic images were digitized off-line into a 256 X 256 pixel matrix with 256 gray levels/pixel. Two end-diastolic frames prior to contrast appearance were averaged to obtain a mask that was subtracted from end-diastolic contrast frames corresponding to the two beats of peak intensity. The same procedure was repeated for the systolic frames. LV edges from echocardiographic images prior to contrast appearance, from digitally subtracted echo-contrast images, and from VGRAM were traced on two occasions by two different observers. LV volumes were calculated by single-plane Simpson's rule and EF was derived by the classical equation. The intra- and interobserver reproducibility in the measurement of EF was excellent for VGRAM (r = 0.95 and 0.94, respectively), it was good for two-dimensional echocardiography (r = 0.87 and 0.73), and was fair for contrast-echo (r = 0.79 and 0.68).(ABSTRACT TRUNCATED AT 250 WORDS)