In idiopathic dilated cardiomyopathy (IDC), an impaired left ventricular filling as assessed by the Doppler echocardiographic mitral flow pattern is closely related to the severity of congestive heart failure. This study examined the relation of left ventricular filling and the clinical course of the disease in patients with a recent diagnostic procedure and initiation of medical therapy (group 1, n = 15) as compared with patients in a chronic stage of the disease (group 2, n = 24) with the diagnosis established > 1 year before. All patients had to be in sinus rhythm to facilitate the Doppler echocardiographic evaluation of left ventricular filling. The clinical status was assessed by the New York Heart Association classification and a heart failure score at baseline and after a period of 12 +/- 7 months. At baseline the ratio of the peak early/atrial Doppler velocities (VE/VA) was shifted toward the early diastole in group 1 as compared to group 2 (1.84 +/- 1.02 vs 1.12 +/- 0.55; p < 0.05). Symptoms of heart failure were more severe in group 1. During follow-up, VE/VA tended to decrease in group 1 from 1.84 +/- 1.02 to 1.35 +/- 1.03 (p = 0.07) and remained unchanged in group 2 (1.12 +/- 0.55 and 1.34 +/- 1.23; not significant). In a subgroup of 10 patients who underwent repeat right heart catheterization, the decrease of VE/VA coincided with a decrease of the pulmonary capillary wedge pressure.(ABSTRACT TRUNCATED AT 250 WORDS)