Background: It is well-known that responses to medical management are heterogenous in patients with chronic heart failure. We investigated the role of contractile reserve in predicting response to medical management in nonischemic dilated cardiomyopathy. We also evaluated the usefulness of LV synchrony measured by tissue Doppler imaging (TDI) at rest and with low-dose dobutamine for predicting response to medical management. Methods: Nineteen patients (mean age: 52 짹 0.5 yrs, women: 9) who were followed for at least 3 months with the diagnosis of idiopathic dilated cardiomyopathy (LV ejection fraction < 40%) were enrolled. Ischemic heart disease was excluded by coronary angiography or myocardial SPECT. At baseline, comprehensive echocardiographic examination was performed and LV volume was measured by biplane Simpson method. Also, TDI was performed using a 6-basal, 6-mid segmental model to assess the time from R wave to peak systolic velocity (Ts). The standard deviation (SD) of Ts was an indicator of systolic synchrony. The measurements were repeated with dobutamine infusion at 10mcg/kg/min. After 6 months of medical therapy with angiotensin-converting enzyme inhibitors and/or beta-blockers, follow-up echocardiography was performed. Results: After 6 months of medical management, LVEF was significantly improved (32.9 짹 10.5% vs 36.7 짹 8.8%, p=0.05) but standard deviation of Ts was not significantly different from baseline (66 짹 48 vs 62 짹 42 msec). Forty-two percent of patients showed more than 10% improvement in LVEF whereas 26% of patients showed decrease of LVEF. Changes of LVEF at 6 month follow up were correlated with DLVEF with dobutamine infusion (r=0.6, p<0.01). Also, positive correlation was observed between D standard deviation of Ts after dobutamine and Dstandard deviation of Ts after 6 month-follow up (r=0.712, p<0.05). However, there was no significant correlation between standard deviation of Ts and the change of LVEF at 6 month-follow up. Conclusion: Changes of LVEF and LV synchrony with low-dose dobutamine appear to be useful for predicting the response to medical management in patients with nonischemic cardiomyopathy.