NEW METHOD FOR EVALUATING LEFT-VENTRICULAR WALL-MOTION BY COLOR-CODEDTISSUE DOPPLER IMAGING - IN-VITRO AND IN-VIVO STUDIES

Objectives. The aim of this study was to examine the accuracy and vali dity of a newly developed tissue Doppler imaging system in in vitro an d in vivo studies. Background. Because quantitative measurement of wal l motion velocity in real time is still difficult by conventional echa cardiography, we developed a new system for evaluating ventricular wal l motion by analyzing Doppler signals from cardiac tissue. Methods. We used a modified Doppler color imaging system, omitting the high pass filter to allow Doppler signals from cardiac tissue to enter the auto correlator. Ultrasound carrier and pulse repetition frequencies were 3 .75 MHz and 3.0 to 6.0 kHz,respectively. Under these conditions, the l owest measurable velocity was 0.2 cm/s. Results. In the rotating spong e model, the measured velocity correlated well with the actual velocit y (y = 0.97x + 2.17, r = 0.99). In clinical settings, the mid-ejection mean velocity at either endocardial or epicardial sites of the left v entricular posterior wall measured by M-mode tissue Doppler imaging co rrelated well with that measured by conventional M-mode echocardiograp hy (y = 0.94x + 0.64, r = 0.99) During systole, in healthy subjects, t he anterior left ventricular wall was color coded blue and the posteri or wall was color coded red, whereas the akinetic regions associated w ith myocardial infarction showed no color throughout the cardiac cycle . The ventricular posterior wall excursion velocity, defined as the di fference between velocities at the endocardial and epicardial sites, w as significantly slower in patients with dilated cardiomyopathy (0.4 /- 0.3 cm/s) than in normal subjects (2.0 +/- 0.6 cm/s). Conclusions. These results indicate that the present system accurately represents t issue velocity and can create two-dimensional color images that facili tate visual assessment of ventricular wall motion.