| Objective: To investigate whether dobutamine could induce or worsen abnormal contractile responses in patients with idiopathic dilated cardiomyopathy (IDC), and to investigate electromechanical activity synchronism and heart systolic and diastolic function in EDC.Methods: Eighteen patients with IDC ( mean age 48.8 ±14.1 years, New York Heart Association class II-III, mean left ventricular ejection fraction 33.2 ± 9.2%) underwent low dosage dobutamine stess echocardiography (5-10-20ug/kg . min). Wall motion and thickening was assessed in 16 segments using a four-point scale recommended by the American Society of Echocardiography. Transthoracic echocardiograms was reorded with the use of a HP Sonos 5500 color echocardiographic diagnostic system. During dobutamine infusion, abnormally contracting segments were classified into four different patterns of contractile response: improved (wall motion score decreased >1 point compared with base or upper level ), unchanged, worsened (wall motion score increased >1 point compared with base or upper level ), and biphasic (i.e., improvement at low dosage dobutamine followed by worsening at peak stress). Abnormal contractile responses was defined as unchanged, worsened, and biphasic segments. Among them, worsened and biphasic segments were judged to be ischemia-like responses.Apical four-chamber, five-chamber, and anterior and posterior atrioventricular annulus were recorded during studying electromechanical activity synchronism and cardiac function at rest and each stage of dobutamine infusion. We acquired flow spectrum and left ventricular systolic (LVSEV) and diastolic end volume (LVDEV). Stoke volume (SV) and left ventricular ejective fraction (LVEF) were derived. We measured the peak velocities of early (Ev) and atrial (Av) transmitral flow, the peakvelocities of aortic folw (As), total E wave (ED) and A wave duration, left ventricular filling (FT) and ejective time (ET). The Z ratio and CO were derived by them respectively. The Z ratio was calculated from the sum of FT and ET, derived by the RR interval, and expressed as a percentage. After transferring the image into Doppler tissue imaging (DTI) mode, we recorded the peak systolic velocity (S), the peak early diastolic velocity (E), and the atrial systolic wall motion velocity (A) in atrioventricular annulus. Electromechanical dispersion (Tcd) was derived by electromechanical time. Tcd resembled electromechanical synchronism of left ventricular. We calculated the means of S, E, and A (Sm, Em and Am).Results: Eighteen patients all showed abnormal contracile responses (100%), and thirteen ones were ischemia-like responses (94.4%). In total 225 segments, 126 segments showed abnormal contracile responses (56%). In the middle of them, 29 segments were ischemia-like responses (12.9%), 97 segments were unchanged segments (43.1%), 16 segments were worsened segments (7.1%), and 13 segments were biphasic segments (5.8%). Heart rate, As and CO increased transparently. There were statistical difference in LVSEV, SV, and LVEF between rest and stress, but the total tendency wasn't changed greatly. Ev, Av, and Ev/Av didn't show statistical difference. CO correlated with heart rate statistically. Sm and Em increased with stress dosage, but only 20ug/kg min showed statistical difference comparing with other dosages. Sm correlated with Em positively. Am and Em/Am had no difference at rest and each stage. Corrected Tcd didn't show worsened tendency as anticipation and improvement of synchronism. Remained time intervals (corrected ED, AD, ET, IVRT, and Z ratio) all showed no difference.Conclusion:1. Myocardial abnormal contractile responses could be induced by dobutamine stress echocardiography.2 IDC had ischemia-like energy mismatch between demand and supply which would be related to etiology and progress of IDC.3 Dobutamine could neither improve nor worsen the synchronism of the left ventricular electromechanical activity.4 Low dose dobutamine (<10ug/kg min) could hardly improve cardial function...
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