The aim of this study was to assess whether a sudden increase in left ventricular (LV) afterload in a pre-dilated condition of idiopathic cardiomyopathy, in associated with some non-invasively detectable impairment of LV function. Ten subjects (Group A, 7 males, 3 females, mean age 36.7 +/- 11.4 years), submitted to cardiac catheterization because of severe symptoms related to ventricular arrhythmias, were found to have normal coronary arteries and left ventricular function, but histological features suggestive of congestive cardiomyopathy at endomyocardial biopsy. Echocardiography was performed during handgrip for 5 min at 30% of the maximal effort, in order to obtain a sharp increase in systolic LV pressure of more than 40 mm Hg. Ten healthy subjects were used as controls (Group B). Results in Group A showed a significant decrease in LV ejection fraction (from 62.4 +/- 6.9 to 57 +/- 7; p < 0.005) and LV shortening fraction (from 34.2 +/- 5.1 to 31 +/- 4.3; p < 0.01); a significant increase in LV systolic volume (from 48.2 +/- 9.1 to 60.0 +/- 12.0; p < 0.005) and systolic stress (from 114.6 +/- 33.2 to 178.8 +/- 58.2; p < 0.001). At the first minute of recovery LV function normalized quickly while LV systolic volume remained moderately increased (52.5 +/- 10.2). In conclusion, in pre-congestive dilated cardiomyopathy a latent impairment in LV function can be detected during a sharp increase of LV afterload. Isometric stress is particularly useful in eliciting these transient changes, as the method allows a reliable echocardiographic examination during maximal stress and not only during the recovery phase, as in dynamic stress.