Postsystolic shortening (PSS), a positive myocardial velocity after aortic valve closure as assessed by Doppler tissue imaging, is a common pathologic finding in patients with myocardial disease. Beta-blocker therapy can improve global and regional myocardial function. The aim of the present study was to examine whether the beta-blocker carvedilol might reduce the incidence and magnitude of PSS in patients with idiopathic dilated cardiomyopathy. Before and 2 months after carvedilol therapy, 19 patients (7 men, 12 women; mean age 59 +/- 13 years) underwent conventional echocardiographic assessment and Doppler tissue imaging. Time-velocity curves were constructed at the 12 basal and mid myocardial segments of the left ventricular (LV) walls. PSS was defined if positive myocardial velocity after aortic valve closure was greater than the ejection peak. The number of segments showing PSS was assessed before and after carvedilol therapy. Carvedilol decreased LV end-diastolic dimension (from 66 +/- 5 to 62 +/- 7 mm, p <0.01), increased the LV ejection fraction (from 28 +/- 9% to 36 +/- 8%, p <0.01), and increased early diastolic mitral annular velocity (Ea) (from 5.0 +/- 1.6 to 5.5 +/- 1.7 cm/ms, p <0.01). This was associated with significant reductions in the number of segments showing PSS (from 2.8 +/- 3.0 to 0.8 +/- 1.4, p <0.01). There was a correlation between changes in the number of segments showing PSS and changes in Ea (r = -0.56, p = 0.01). In conclusion, PSS may reflect the severity of LV diastolic function during pharmacologic reverse remodeling in patients with idiopathic dilated cardiomyopathy. These data provide new insights into the mechanisms by which carvedilol improves cardiac function and symptoms in these patients.