34 patients with ventricular dysfunction (18 in NYHA class II and 16 in NYHA class III heart failure) whose clinical status was stabilized by diuretics and systemic vasodilators, entered a randomized trial to compare the effects of short-term oral digoxin and active placebo on left ventricular diastolic function, non invasively evaluated by echo-Doppler transmitral left ventricular filling flow. At baseline patients were subdivided by reversal--the ratio of peak early (E) and late (A) transmitral filling velocities--E/A < 1 (group I) or normal--E/A > or = 1 (group II) echo-Doppler E/A ratio; group II exhibited a shorter deceleration time (125 +/- 20 ms vs 198 +/- 38 ms, p > 0.05) and isovolumic relaxation time (64 +/- 15 ms vs 93 +/- 10 ms; p < 0.05) as well as a higher peak E velocity (85 +/- 28 cm/s vs 54 +/- 20 cm/s; p < 0.05), ("restrictive" left ventricular filling pattern). After 4 weeks, no changes in all echo-Doppler parameters were noted in group I in response to either oral digoxin or active placebo. Clinical amelioration (defined as reduction by at least one functional class) was observed in 3 patients after digoxin.(ABSTRACT TRUNCATED AT 250 WORDS)