The aim for this study was to evaluate the hemodynamic changes that appear in patients with myocardiopathy at functional stage II (NYHA) subjected to standard treatment (digital+diuretics) plus nitrates. We used isosorbide-5-mononitrate (IS-5-MN). We studied 20 patients for 100 days in different phases. The placebo-controlled, crossover, double-blind stage random distribution was from day 2 to 5. From day 6 to 20 all the patients took 40 mg/12 hours of IS-5-MN, taking 40 mg/8 hours of active ingredient from day 21 to 100. We performed basal cycloergometrics 3 and 6 hours after administration on days 2, 5, 20, 34 and 100 of the treatment, as well as echocardiograms on these same days. We compared the results obtained versus placebo (p < 0.05). There were no significant differences in heart rate at rest or systolic arterial tension at rest or maximum. Maximum heart rate increased significantly in the tests at days 34 (basal: 143 +/- 9; 3 hours: 139 +/- 8; 6 hours: 140 +/- 7) and 100 (basal: 145 +/- 7; 3 hours: 141 +/- 8; 6 hours: 142 +/- 6) versus the tests carried out with placebo (basal: 136 +/- 8; 3 hours: 135 +/- 7; 6 hours: 136 +/- 7). There were no differences in the tests after acute dose or at treatment day 20.(ABSTRACT TRUNCATED AT 250 WORDS)