Quantification of incremental alterations in regional myocardial function induced by low dose dobutamine using tissue Doppler imaging

Low dose oobutamine echocardiography has been shown to be useful to detect myocardial viability. However, routine visual wall motion assessment is subjective and the incremental effects of very low dose dobutamine on normal myocardium have not been quantified previously. To objectively quantify the effects of low dose dobutamine on regional ventricular (LV) function, 12 normal subjects had tissue Doppler studies at baseline and during dobutamine infused at 1, 2, 3, and 5 μg/kg/min. The tissue Doppler system (Toshiba 380A) was interfaced with a computer which converted color-coded video data into a 35 pixel/cm × 0.1 sec digital velocity matrix.. Anteroseptal and posterior wall (example shown) endocardial time-velocity plots were analyzed for each staee (ANOVA for reneated measures) Significant changes from baseline were detected with only 2 μg/kg/min: peak systolic velocity increased from 44 ±7 to 56 ±10*mm/sec and systolic time-velocity integral (TVI) increased from 7.5 ±2.2 to 9.8 ±2.3 mm (*p<0.02 vs. baseline). Further significant alterations occurred from 3 to 5 μg/kg/min: peak systolic velocity increased from 60 ±12 to 77 ±14**mm/sec and TVI increased from 10.2 ±2.5 to 12.5 ±3.1**mm (**p<0.002 vs. 3 μg/kg/min). Heart rate was unchanged throughout the protocol. Conclusion: Tissue Doppler velocity has potential to objectively quantify incremental alterations in regional myocardial function induced by very low dose dobutamine.