QUANTIFICATION OF THE MYOCARDIAL RESPONSE TO LOW-DOSE DOBUTAMINE USING TISSUE DOPPLER-ECHOCARDIOGRAPHIC MEASURES OF VELOCITY AND VELOCITY-GRADIENT

Low-dose dobutamine echocardiography has been clinically useful in myo cardial viability studies, although routine visual assessment of wall motion is subjective. The objective was to quantify the incremental my ocardial response to low-dose dobutamine infusion using a new semiauto mated tissue Doppler (TD) analysis system and to compare these data wi th routine echocardiographic measures in the same subjects. Twelve sub jects had TD and routine echocardiographic studies at baseline and dur ing 10-minute stages of dobutamine infusion at 1, 2, 3, and 5 mu g/kg/ min. Color TD video data were converted to a digital velocity matrix ( 4.5 velocity data points/mm at 500 Hz) for analysis of mitral annular velocity, endocardial velocity, and velocity gradient at each stage. P osterior wall percent thickening and ejection fraction were calculated from the routine images. Mitral annular peak systolic velocity signif icantly increased with only 1 mu g/kg/min of dobutamine 69 +/- 9 to 77 +/- 7 mm/s (p < 0.05 vs baseline), and further incremental increases occurred with each subsequent dose. Anteroseptal and posterior wall pe ak endocardial velocity increased with 2 mu g/kg/min of dobutamine fro m 33 +/- 7 to 46 +/- 15 mm/s and 50 +/- 9 to 61 +/- 10 mm/s, respectiv ely (p < 0.01 vs baseline) and further increased with 5 mu g/kg/min (p < 0.0001 vs 3 mu g/kg/min). Posterior wall peak systolic gradient als o increased with 2 mu g/kg/min of dobutamine from 3.1 +/- 0.6 to 5.4 /- 1.6 s(-1) (p < 0.05 vs baseline). Routine measures of percent wall thickening or ejection fraction did not detect increases until the 3 m u g/kg/min dose. TD can detect subtle alterations in contractility ind uced by low-dose dobutamine and has the potential to quantify regional ventricular function objectively. (C) 1998 by Excerpta Medica, Inc.