Identification Of Viable Myocardium By Using Low Dose Dobutamine Echocardiography Combined With Doppler Tissue Imaging

Assessing viable myocardium early after thrombolytic therapy on acute myocardial infarction is of great prognostic and therapeautic significance .To evaluate the predicting value and safety of conventional low dose dobutamine stress echocardiography(LDDSE) as well as the feasibility of combining with Doppler tissue imaging(DTI) in identification of viable myocardium, 12patients with primary acute myocardial infarction were selected. Each underwent LDDSE 7.5+1.0 days after acute myocardial infarction. 16-segment model and semi quantitative analysis method were taken. We selected 33 segments which show hypokinetic or akinetic at resting echocardiography to undergo identification ofviability.Pulsed-wave Doppler tissue imaging(PW-DTI) was recorded at mid-point of endocardium of every selected segment, at inner and outer mitral annul us as well.Then we measured the parameters. Furthermore, at 1 month after acute myocardial infarction, a follow-up was taken. The main results were:1.18 out of 33 segments showed improvement of wall motion during LDDSE, and among these 12 segments were viable at foliow-up(score was decreased by more than 1).Although the rest (14" segments) showed no change during LDDSE, two of them were viable at follow-up. The sensitivity, specificity, positive predicting value, negative predictive value and accuracy of LDDSE test in assessing viable myocardium are 85.7%,68.5%,66.7%,86.7%and75.8%, respectively.Two patients' tests were interrupted because their electrocardiogram showed elevated ST segment, and one patient didn't continue his test on account of frequent ventricular premature .No severe responses were observed.2.PW-DTI was feasible in 27 out of 33 segments. These segments weredivided into viable myocardium (group A) and non-viable myocardium (group B) depending on the improvement of wall motion at follow-up. During LDDSE group A and group B showed the tendency of increased peak velocity of ejection phrase (Vs).However, the Vs of group A was larger than group B at each dosageCompared with resting state ,the increase of Vs in group A was larger than group B at end-point(3.26+1.49cm/s VS 2.13+1.21 cm/s,P<0.05).The rest parameters didn't show obviously regular change during LDDSE.3.1 month after acute myocardial infarction, routine indexes of heart function and peak velocity of ejection phase( Vs),peak velocity of early diastole ( Ve), peak velocity of late diastole (Va), the ratio of e to a(e/a) at inner and outer mitral annulus showed no significance compared with resting states.Conclusion: 1. Conventional LDDSE is a safe and convenient method in evaluating viable myocardium of patients with acute myocardial infarction, and it can predict the improvement of regional wall motion; 2.PW-DTI combined with LDDSE in identification of viable myocardium is feasible, Vs may be the main parameter.