Myocardial hypertrophy and interstitial fibrosis are common in acromegalic hearts and may induce left ventricular (LV) dysfunction. The transmitral flow pattern was examined by pulsed-wave Doppler in 20 patients with active acromegaly and nine with acromegaly cured by pituitary microsurgery. Control groups consisted of 25 normal subjects and 13 patients with systemic hypertension. We related Doppler indices of LV filling (E and A peak velocities and E/A ratio) to the duration of acromegalic disease, the GH plasma levels and LV mass. The LV mass/BSA was significantly greater in active acromegaly (187 +/- 53 g/sq m) and systemic hypertension groups (161 +/- 48 g/sq m) than in cured acromegaly (125 +/- 35 g/sq m) and the normal control group (109 +/- 36 g/sq m) (p < 0.01 for both). No differences were found in the E peak velocity, A peak velocity, and E/A ratio in the groups with active acromegaly (E/A: 0.9 +/- 0.2), cured acromegaly (E/A: 0.9 +/- 0.3), and systemic hypertension (E/A: 0.8 +/- 0.5). An E/A ratio < 1 was found in 13 patients with active and four with cured acromegaly; (p = NS). In the active acromegaly group, the E/A ratio was related to either LV mass or the duration of disease (r:-0.45 and -0.47, respectively; p < 0.05). In the cured acromegaly group, the E/A ratio was related to the duration of disease before surgery (r:-0.70; p < 0.05) and not to LV mass (r:0.12). In conclusion, an impairment in LV filling may be present not only in the patients with active acromegaly but also in those successfully treated by surgery after a long duration of the disease, despite normal LV mass. These LV filling abnormalities may be in part determined by nonreversible myocardial changes, such as interstitial tissue fibrosis.